Lathe: Work Centeringthe Mechanic

Lathe Machine Repair Service, Lathe Repair Services Providers in India. Get contact details and address of Lathe Machine Repair Service, Lathe Repair Services firms and companies. LATHE The lathe is a machine tool used principally for shaping pieces of metal (and sometimes wood or other materials) by causing the workpiece to be held and rotated by the lathe while a tool bit is advanced into the work causing the cutting action. The basic lathe that. Nov 20, 2020 Aftermath released of Russian worker killed, sucked in by lathe machine in metal factory in Russia. OG video here: Man dies after getting sucked in by machine at work inside metal factory in Russia WORK ACCIDENT: Farm worker decapitated & dismembered by agricultural machinery. This lathe will take some cleaning and adjustment to really work well, but for the price it is a good deal. There is so much information on the internet about set-up, improvement, use, and projects to make with this lathe.

  1. Lathe: Work Centering The Mechanic Tools
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Engine lathe’s attachments accessories

Engine lathe’s attachments accessories


This chapter will help you to identify the engine lathe’s attachments, accessories, and their uses. Also, it will identify and explain different machining operations and the factors related to machining operations. Of course, you will be expected to know and to follow the safety precautions associated with machining operations.
There are a number of different types of lathes installed in the machine shops. These include the engine lathe, the horizontal turret lathe, and several variations of the basic engine lathe, such as bench, toolroom, and gap lathes. All lathes, except the vertical turret type, have one thing in common. For all usual machining operations, the workpiece is held and rotated about a horizontal axis, while being formed to size and shape by a cutting tool. In the vertical turret lathe, the workpiece is rotated about a vertical axis. Of the various types of lathes, the type you are most likely to use is the engine lathe. Therefore, this chapter deals only with engine lathes and the machining operations you may have to perform.
NOTE: Before you attempt to operate any lathe, make sure you know how to operate it. Read all operating instructions supplied with the machine. Learn the locations of the various controls and how to operate them.
An engine lathe similar to the one shown in figure below is found in every machine shop. It is used mostly for
Figure—Typical engine lathe.
turning, boring, facing, and thread cutting. But it may also be used for drilling, reaming, knurling, grinding, spinning, and spring winding. Since you will primarily be concerned with turning, boring, facing, and thread cutting, we will deal primarily with those operations in this chapter.
The work held in the engine lathe can be revolved at any one of a number of different speeds, and the cutting tool can be accurately controlled by hand or power for longitudinal feed and cross feed. (Longitudinal feed is the movement of the cutting tool parallel to the axis of the lathe; cross feed is the movement of the cutting tool perpendicular to the axis of the lathe.)
Lathe size is determined by two measurements: (1) the diameter of work it will swing (turn) over the ways and (2) the length of the bed. For example, a 14-inch by 6-foot lathe will swing work up to 14 inches in diameter and has a bed that is 6 feet long.
Engine lathes vary in size from small bench lathes that have a swing of 9 inches to very large lathes for turning large diameter work such as low-pressure turbine rotors. The 16-inch lathe is the average size for general purposes and is the size usually installed in ships that have only one lathe.

To learn the operation of the lathe, you must be familiar with the names and functions of the principal parts. Lathes from different manufacturers differ somewhat in construction, but all are built to perform the same general functions. As you read the description of each part, find its location on the lathe in figure and the figures that follow. (For specific details of features of construction and operating techniques, refer to the manufacturer’s technical manual for your machine.)
Bed and Ways
The bed is the base or foundation of the parts of the lathe. The main feature of the bed is the ways, which are formed on the bed’s upper surface and run the full length of the bed. The ways keep the tailstock and the carriage, which slide on them, in alignment with the headstock.
The headstock contains the headstock spindle and the mechanism for driving it. In the belt-driven type, shown in figure, the driving mechanism consists of
Figure—Belt-driven type of headstock.
a motor-driven cone pulley that drives the spindle cone pulley through a drive belt. The spindle can be rotated either directly or through back gears.
When the headstock is set up for direct drive, a bull-gear pin, located under a cover to the right of the spindle pulley, connects the pulley to the spindle. This connection causes the spindle to turn at the same speed as the spindle pulley.
When the headstock is set up for gear drive, the bull-gear pin is pulled out, disconnecting the spindle pulley from the spindle. This allows the spindle to turn freely inside the spindle pulley. The back-gear lever, on the left end of the headstock, is moved to engage the back-gear set with a gear on the end of the spindle and a gear on the end of the spindle pulley. In this drive mode, the drive belt turns the spindle pulley, which turns the back-gear set, which turns the spindle. Each drive mode provides four spindle speeds, for a total of eight. The back-gear drive speeds are less slower than the direct-drive speeds.

Lathe: work centering the mechanic software

The primary purpose of the tailstock is to hold the dead center to support one end of the work being
Figure—Side view of a carriage mounted on a bed.
machined. However, the tailstock can also be used to hold tapered shank drills, reamers, and drill chucks. It can be moved on the ways along the length of the bed and can be clamped in the desired position by tightening the tailstock clamping nut. This movement allows for the turning of different lengths of work. The tailstock can be adjusted laterally (front to back) to cut a taper by loosening the clamping screws at the bottom of the tailstock.
Before you insert a dead center, drill, or reamer, carefully clean the tapered shank and wipe out the tapered hole of the tailstock spindle. When you hold drills or reamers in the tapered hole of the spindle, be sure they are tight enough so they will not revolve. If you allow them to revolve, they will score the tapered hole and destroy its accuracy.
The carriage is the movable support for the crossfeed slide and the compound rest. The compound rest carries the cutting tool in the tool post. Figure 9-3 shows how the carriage travels along the bed over which it slides on the outboard ways.
The carriage has T-slots or tapped holes to use for clamping work for boring or milling. When the carriage is used for boring and milling operations, carriage movement feeds the work to the cutting tool, which is rotated by the headstock spindle.
You can lock the carriage in any position on the bed by tightening the carriage clamp screw. But you do this only when you do such work as facing or parting-off, for which longitudinal feed is not required. Normally the carriage clamp is kept in the released position. Always move the carriage by hand to be sure it is free before you engage its automatic feed.
The apron is attached to the front of the carriage and contains the mechanism that controls the movement of the carriage and the crossslide.
Feed Rod
The feed rod transmits power to the apron to drive the longitudinal feed and crossfeed mechanisms. The feed rod is driven by the spindle through a train of gears. The ratio of feed rod speed to spindle speed can be varied by using change gears to produce various rates of feed.
Figure—Compound rest.
The rotating feed rod drives gears in the apron; these gears in turn drive the longitudinal feed and crossfeed mechanisms through friction clutches.
Some lathes do not have a separate feed rod, but use a spline in the lead screw for the same purpose.
Lead Screw
The lead screw is used for thread cutting. It has accurately cut Acme threads along its length that engage the threads of half-nuts in the apron when the half-nuts are clamped over it. The lead screw is driven by the spindle through a gear train. Therefore, the rotation of the lead screw bears a direct relation to the rotation of the spindle. When the half-nuts are engaged, the longitudinal movement of the carriage is controlled directly by the spindle rotation. Consequently, the cutting tool is moved a definite distance along the work for each revolution that the spindle makes.
Crossfeed Slide
The crossfeed slide is mounted to the top of the carriage in a dovetail and moves on the carriage at a right angle to the axis of the lathe. A crossfeed screw allows the slide to be moved toward or away from the work in accurate increments.
Compound Rest
The compound rest, mounted on the compound slide, provides a rigid adjustable mounting for the cutting tool. The compound rest assembly has the following principal parts:
1. The compound rest SWIVEL, which can be swung around to any desired angle and clamped in position. It is graduated over an arc of 90° on each side of its center position for easier setting to the angle selected. This feature is used for machining short, steep tapers, such as the angle on bevel gears, valve disks, and lathe centers.
2. The compound rest, or TOP SLIDE, which is mounted on the swivel section on a dovetailed slide. It is moved by the compound rest feed screw.
Figure—Common types of toolholders.
Figure—Knurling and threading toolholders.

This arrangement permits feeding the tool to the work at any angle (determined by the angular setting of the swivel section). The graduated collars on the crossfeed and compound rest feed screws read in thousandths of an inch for fine adjustment in regulating the depth of cut.
Accessories and Attachments
Accessories are the tools and equipment used in routine lathe machining operations. Attachments are special fixtures that may be mounted on the lathe to expand the use of the lathe to include taper cutting, milling, and grinding. Some of the common accessories and attachments are described in the following paragraphs.
TOOL POST.—The sole purpose of the tool post is to provide a rigid support for the tool. It is mounted in the T-slot of the compound rest. A forged tool or a toolholder is inserted in the slot in the tool post. By tightening a setscrew, you will firmly clamp the whole unit in place with the tool in the desired position.
TOOLHOLDERS—Some of the common toolholders used in lathe work are illustrated in figure . Notice the angles at which the tool bits are set in the various holders. These angles must be considered with respect to the angles ground on the tools and the angle that the toolholder is set with respect to the axis of the work.
Two types of toolholders that differ slightly from the common toolholders are those used for threading and knurling.
The threading toolholder has a formed cutter which needs to be ground only on the top surface for sharpening. Since the thread form is accurately shaped
Figure—Lathe tools and their applications.
over a large arc of the tool, as the surface is worn away by grinding, the cutter can be rotated to the correct position and secured by the setscrew.
A knurling toolholder carries two knurled rollers which impress their patterns on the work as it revolves. The purpose of the knurling tool is to provide a roughened surface on round metal parts, such as knobs, to give a better grip in handling. The knurled rollers come in a variety of patterns.
ENGINE LATHE TOOLS.—Figure shows the most popular shapes of ground lathe cutter bits and their applications. In the following paragraphs we will discuss each of the types shown.
Left-Hand Turning Tool.—This tool is ground for machining work when it is fed from left to right, as indicated in figure below, view A. The cutting edge is on the right side of the tool, and the top of the tool slopes down away from the cutting edge.
Figure–A. Four-Jaw chuck. B. Three-Jaw chuck.
Round-Nosed Turning Tool.–This tool is for general-purpose machine work and is used for taking light roughing cuts and finishing cuts. Usually, the top of the cutter bit is ground with side rake so the tool may be fed from right to left. Sometimes this cutter bit is ground flat on top so the tool may be fed in either direction ( view B).
Right-Hand Turning Tool.–This is just the opposite of the left-hand turning tool and is designed to cut when it is fed from right to left ( view C). The cutting edge is on the left side. This is an ideal tool for taking roughing cuts and for all-around machine work.
Left-Hand Facing Tool.–This tool is intended for facing on the left-hand side of the work (view D). The direction of feed is away from the lathe center. The cutting edge is on the right-hand side of the tool, and the point of the tool is sharp to permit machining a square corner.
Threading Tool.–The point of the threading tool is ground to a 60-degree included angle for machining V-form screw threads (view E). Usually, the top of the tool is ground flat, and there is clearance on both sides of the tool so it will cut on both sides.
Right-Hand Facing Tool.–This tool is just the opposite of the left-hand facing tool and is intended for facing the right end of the work and for machining the right side of a shoulder (view F).
Square-Nosed Parting (Cutoff) Tool.–The principal cutting edge of this tool is on the front (view G). Both sides of the tool must have sufficient clearance to prevent binding and should be ground slightly narrower at the back than at the cutting edge. This tool is convenient for machining necks and grooves and for squaring comers and cutting off.
Boring Tool.–The boring tool ( view H) is usually ground the same shape as the left-hand turning
Figure –Draw-in collet chuck.
Figure —Faceplate.
tool so that the cutting edge is on the right side of the cutter bit and may be fed in toward the headstock.
Inside-Threading Tool.—The inside-threading tool ( view J) has the same shape as the threading tool in figure ( view E), but it is usually much smaller. Boring and inside-threading tools may require larger relief angles when used in small diameter holes.
LATHE CHUCKS.—The lathe chuck is a device for holding lathe work. It is mounted on the nose of the spindle. The work is held by jaws which can be moved in radial slots toward the center of the chuck to clamp down on the sides of the work. These jaws are moved in and out by screws turned by a special chuck wrench.
The four-jaw independent lathe chuck, view A in figure , is the most practical chuck for general work The four jaws are adjusted one at a time, making it possible to hold work of various shapes and to adjust the center of the work to coincide with the axis of the spindle. The jaws are reversible.
The three-jaw universal or scroll chuck, view B in figure, can be used only for holding round or hexagonal work All three jaws move in and out together in one operation and bring the work on center automatically. This chuck is easier to operate than the four-jaw type, but, when its parts become worn, its accuracy in centering cannot be relied upon. Proper lubrication and constant care are necessary to ensure reliability.
The draw-in collet chuck is used to hold small work for machining in the lathe. It is the most accurate type of chuck made and is intended for precision work. Figure shows the parts assembled in place in the lathe spindle. The collet, which holds the work, is a split-cylinder with an outside taper that fits into the tapered closing sleeve and screws into the threaded end of the hollow drawbar. As the handwheel is turned clockwise, the drawbar is moved toward the handwheel. This tightening up on the drawbar pulls the collet back into the tapered sleeve, thereby closing it firmly over the work and centering the work accurately and quickly. The size of the hole in the collet determines the diameter of the work the chuck can handle.
The faceplate is used for holding work that, because of its shape and dimensions, cannot be swung between centers or in a chuck. The T-slots and other openings on its surface provide convenient anchors for bolts and clamps used in securing the work to it. The faceplate is mounted on the nose of the spindle.
The driving plate is similar to a small faceplate and is used mainly for driving work that is held between centers. The primary difference between a faceplate and a driving plate is that a faceplate has a machined face for precision mounting, while the face of a driving plate is left rough. When a driving plate is used, the bent tail of a dog clamped to the work is inserted into a slot in the faceplate. This transmits rotary motion to the work.
Figure —60-degree lathe centers.
Figure —Lathe dogs.
Lathe Centers
The 60-degree lathe centers shown in figure provide a way to hold the work so it can be turned accurately on its axis. The headstock spindle center is called the LIVE CENTER because it revolves with the work. The tailstock center is called the DEAD CENTER because it does not turn. Both live and dead centers have shanks turned to a Morse taper to fit the tapered holes in the spindles; both have points finished to an angle of 60°. They differ only in that the dead center is hardened and tempered to resist the wearing effect of the work revolving on it. The live center revolves with the work and is usually left soft. The dead center and live center must NEVER be interchanged. (There is a groove around the hardened dead center to distinguish it from the live center.)
The centers fit snugly in the tapered holes of the headstock and tailstock spindles. If chips, dirt, or burrs prevent a perfect fit in the spindles, the centers will not run true.
To remove the headstock center, insert a brass rod through the spindle hole and tap the center to jar it loose; then pull it out with your hand. To remove the tailstock center, run the spindle back as far as it will go by turning the handwheel to the left. When the end of the tailstock
Figure —Center rest.
screw bumps the back of the center, it will force the center out of the tapered hole.
Lathe Dogs
Lathe dogs are used with a driving plate or faceplate to drive work being machined on centers; the frictional contact alone between the live center and the work is not sufficient to drive the work
The common lathe dog, shown at the left in figure , is used for round work or work having a regular section (square, hexagon, octagon). The piece to be turned is held firmly in the hole (A) by the setscrew (B). The bent tail (C) projects through a slot or hole in the driving plate or faceplate so that when the tail revolves with the spindle it turns the work with it. The clamp dog, illustrated at the right in figure , may be used for rectangular or irregularly shaped work. Such work is clamped between the jaws,
Center Rest
The center rest, also called the steady rest, is used for the following purposes:
1. To provide an intermediate support for long slender bars or shafts being machined between centers. The center rest prevents them from springing, or sagging, as a result of their otherwise unsupported weight.
Figure —Follower rest.

Figure —Taper attachment.
2. To support and provide a center bearing for one end of the work, such as a shaft, being bored or drilled from the end when it is too long to be supported by a chuck alone. The center rest is clamped in the desired position on the bed and is kept aligned by the ways, as illustrated in figure . The jaws (A) must be carefully adjusted to allow the work (B) to turn freely and at the same time remain accurately centered on the axis of the lathe. The top half of the frame is a hinged section (C) for easier positioning without having to remove the work from the centers or to change the position of the jaws.
Follower Rest
The follower rest is used to back up small diameter work to keep it from springing under the cutting
Figure —Thread dial Indicator.
pressure. It can be set to either precede or follow the cutting action. As shown in figure, it is attached directly to the saddle by bolts (B). The adjustable jaws bear directly on the part of the work opposite the cutting tool.
Taper Attachment
The taper attachment, illustrated in figure , is used for turning and boring tapers. It is bolted to the back of the carriage. In operation, it is connected to the cross slide so that it moves the cross slide traversely as the carriage moves longitudinally, thereby causing the cutting tool to move at an angle to the axis of the work to produce a taper.
The desired angle of taper is set on the guide bar of the attachment. The guide bar support is clamped to the lathe bed Since the cross slide is connected to a shoe that slides on this guide bar, the tool follows along a line parallel to the guide bar and at an angle to the work axis corresponding to the desired taper.
The operation of the taper attachment will be further explained under the subject of taper work
Thread Dial Indicator
The thread dial indicator, shown in figure , eliminates the need to reverse the lathe to return the carriage to the starting point each time a successive threading cut is taken. The dial, which is geared to the lead screw, indicates when to clamp the half-nuts on the lead screw for the next cut.
The threading dial consists of a worm wheel which is attached to the lower end of a shaft and meshed with
Figure —Micrometer carriage stop.
the lead screw. On the upper end of the shaft is the dial. As the lead screw revolves, the dial is turned and the graduations on the dial indicate points at which the half-nuts may be engaged.
Carriage Stop
The carriage stop can be attached to the bed at any point where the carriage should stop. It is used primarily for turning, facing, or boring duplicate parts, as it eliminates taking repeated measurements of the same dimension. In operation, the stop is set at the point where the feed should stop. To use the stop, just before the carriage reaches the stopping point, shut off the automatic feed and manually run the carriage up against the stop. Carriage stops are provided with or without micrometer adjustment. Figure shows a micrometer carriage stop. Clamp it on the ways in the approximate position required, and then adjust it to the exact setting by using the micrometer adjustment. (Do not confuse this stop with the automatic carriage stop that automatically stops the carriage by disengaging the feed or stopping the lathe.)
Every lathe must be maintained strictly according to requirements of the Maintenance and Material Management (3-M) Systems. The first requirement of maintenance to your lathe is proper lubrication. Make it a point to oil your lathe daily where oil holes are provided. Oil the ways daily-not only for lubrication but to protect their scraped surfaces. Oil the lead screw often while it is in use; this is necessary to preserve its accuracy, for a worn lead screw lacks precision in thread cutting. Make sure the headstock is filled to the proper oil level; drain the oil out and replace it when it becomes dirty or gummy. If your lathe is equipped with an automatic oiling system for some parts, make sure all those parts are getting oil. Make it a habit to CHECK frequently to see that all moving parts are being lubricated.
Before engaging the longitudinal ‘feed, be certain that the carriage clamp screw is loose and that the carriage can be moved by hand. Avoid running the carriage against the headstock or tailstock while it is under the power feed; running the carriage against the headstock or tailstock puts an unnecessary strain on the lathe and may jam the gears.
Do not neglect the motor just because it may be out of sight; check its lubrication. If it does not run properly, notify the Electrician’s Mate who is responsible for caring for it. He or she will cooperate with you to keep it in good condition. On lathes with a belt driven from the motor, avoid getting oil or grease on the belt when you oil the lathe or motor.
Keep your lathe clean. A clean and orderly machine is an indication of a good mechanic. Dirt and chips on the ways, on the lead screw, and on the crossfeed screws will cause serious wear and impair the accuracy of the machine.
NEVER put wrenches, files, or other tools on the ways. If you must keep tools on the bed, use a board to protect the finished surfaces of the ways.
NEVER use the bed or carriage as an anvil. Remember, the lathe is a precision machine, and nothing must be allowed to destroy its accuracy.
A knowledge of the basic setup is required if you are to become proficient in performing machine work with a lathe. Some of these setups are considered in the following sections.
Cutting Speeds and Feeds
Cutting speed is the rate at which the surface of the work passes the point of the cutting tool. It is expressed in feet per minute (fpm).
Feed is the amount the tool advances for each revolution of the work. It is usually expressed in thousandths of an inch per revolution of the spindle. Cutting speeds and tool feeds are determined by various considerations: the hardness and toughness of the metal being cut; the quality, shape, and sharpness of the cutting tool; the depth of the cut; the tendency of the work to spring away from the tool; and the strength and power of the lathe. Since conditions vary, it is good practice to find out what the tool and work will stand and then select the most practical and efficient speed and feed for the finish desired.
When ROUGHING parts down to size, use the greatest depth of cut and feed per revolution that the work, the machine, and the tool will stand at the highest practical speed. On many pieces where tool failure is the limiting factor in the size of the roughing cut, you may be able to reduce the speed slightly and increase the feed to remove more metal. This will prolong tool life. Consider an example where the depth of cut is 1/4 inch, the feed 0.020 inch per revolution, and the speed 80 fpm. If the tool will not permit additional feed at this speed, you can drop the speed to 60 fpm and increase the feed to about 0.040 inch per revolution without having tool trouble. The speed is therefore reduced 25 percent, but the feed is increased 100 percent. Thus the actual time required to complete the work is less with the second setup.
For the FINISH TURNING OPERATION, take a very light cut, since you removed most of the stock during the roughing cut. Use a fine feed to run at a high surface speed. Try a 50 percent increase in speed over the roughing speed. In some cases, the finishing speed may be twice the roughing speed. In any event, run the work as fast as the tool will withstand to obtain the maximum speed during this operation. Be sure to use a sharp tool when you are finish turning.

A cutting lubricant serves two main purposes: (1) It cools the tool by absorbing a portion of the heat and reducing the friction between the tool and the metal being cut. (2) It also keeps the cutting edge of the tool flushed clean.
The best lubricants to use for cutting metal must often be determined by experiment. Water-soluble oil is acceptable for most common metals. Special cutting compounds containing such ingredients as tallow, graphite, and lard, marketed under various names, are also used. But these are expensive and used mainly in manufacturing where high cutting speeds are the rule.
Some common materials and their cutting lubricants are as follows:
A lubricant is more important for threading than for straight turning. Mineral lard oil is recommended for threading the majority of metals that are used by the Navy.
Chatter is vibration in either the tool or the work The finished work surface appears to have a grooved or lined finish instead of a smooth surface. The vibration is set up by a weakness in the work, work support, tool, or tool support and is probably the most elusive thing you will find in the entire field of machine work As a general rule, strengthening the various parts of the tool support train will help. It is also advisable to support the work by a center rest or follower rest.
The fault may be in the machine adjustments. Gibs may be too loose; hearings may, after a long period of heavy service, be worn; the tool may be sharpened improperly, and so on. If the machine is in excellent condition, the fault may be in the tool or tool setup. Grind the tool with a point or as near a point as the finish specified will permit; avoid a wide, round leading edge on the tool. Reduce the overhang of the tool as much as possible. Be sure all the gib and bearing adjustments are properly made. See that the work receives proper support for the cut and, above all, do not try to turn at a surface speed that is too high. Excessive speed is probably the greatest cause of chatter. The first thing you should do when chatter occurs is reduce the speed.
Direction of Feed
Regardless of how the work is held in the lathe, the tool should feed toward the headstock. This causes most
Figure —Checking a center’s point with a center gauge.
of the pressure of the cut to bear on the work-holding device and the spindle thrust bearings. When you must feed the cutting tool toward the tailstock, take lighter cuts at reduced feeds. In facing, the general practice is to feed the tool from the center of the workpiece outward.
Before starting a lathe machining operation, always ensure that the machine is set up properly. If the work is mounted between centers, check the alignment of the dead center and the live center and make any necessary changes. Ensure that the toolholder and cutting tool are set at the proper height and angle. Check the work-holding accessory to ensure that the workpiece is held securely. Use the center rest or follower rest to support long workpieces.
The first step in preparing the centers is to see that they are accurately mounted in the headstock and tailstock spindles. The centers and the tapered holes in which they are fitted must be perfectly clean. Chips and dirt left on the contact surfaces prevent the bearing surfaces from fitting perfectly. This will decrease the accuracy of your work. Make sure that there are no burrs in the spindle hole. If you find burrs, remove them by carefully scraping and reaming the hole with a Morse taper reamer. Burrs will produce the same inaccuracies as chips or dirt.
A center’s point must be finished accurately to an angle of 60°. Figure shows the method of checking this angle with a center gauge. The large notch of the center gauge is intended for this purpose. If this test shows that the point is not perfect, you must true it in the lathe by taking a cut over the point with the compound rest set at 30°. You must anneal the hardened tail center before it can be machined in this manner, or you can grind it if a grinding attachment is available.
Figure —Aligning lathe centers.

Figure —Tool overhang.
To turn a shaft straight and true between centers, be sure the centers are aligned in a plane parallel to the ways of the lathe. You can check the approximate alignment of the centers by moving the tailstockup until the centers almost touch and observing their relative positions as shown in figure .
To test center alignment for very accurate work, take a light cut over at each end with a micrometer and, if readings are found to differ, adjust the tailstock accordingly. Repeat the procedure until alignment is obtained.
The first requirement for setting the tool is to have it rigidly mounted on the tool post holder. Be sure the tool sets squarely in the tool post and that the setscrew is tight. Reduce overhang as much as possible to prevent the tool bit from springing during cutting. If the tool has too much spring, the point of the tool will catch in the work, causing chatter and damaging both the tool and the work The distances represented by A and B in figure
Figure —Drilling a center hole.
show the correct overhang for the tool bit and the holder.
The point of the tool must be correctly positioned on the work Place the cutting edge. slightly above the center for straight turning of steel and cast iron and exactly on the center for all other work To set the tool at the height desired, raise or lower the point of the tool by moving the wedge in or out of the tool post ring. By placing the point opposite the tailstock center point, you can adjust the setting accurately.
You cannot perform accurate work if the workpiece is improperly mounted. The requirements for proper mounting are as follows:
1. The work center line must be accurately centered along the axis of the lathe spindle.
2. The work must be held rigidly while being turned.
3. The work must NOT be sprung out of shape by the holding device.
4. The work must be adequately supported against any sagging caused by its own weight and against springing caused by the action of the cutting tool.
There are four general methods of holding work in the lathe: (1) between centers, (2) on a mandrel, (3) in a chuck, and (4) on a faceplate. Work may also be clamped to the carriage for boring and milling, in which case the boring bar or milling cutter is held and driven by the headstock spindle.
Other methods of holding work to suit special conditions are (1) one end on the live center or in a chuck and the other end supported in a center rest, and (2) one end in a chuck and the other end on the dead center.
Holding Work Between Centers
To machine a workpiece between centers, drill center holes in each end to receive the lathe centers. Secure a lathe dog to the workpiece. Then mount the work between the live and dead centers of the lathe.
CENTERING THE WORK.—To center round stock where the ends are to be turned and must be concentric with the unturned body, mount the work on the head spindle in a universal chuck or a draw-in collet chuck If the work is long and too large to pass through the spindle, use a center rest to support one end. Mount a center drill in a drill chuck in the tailstock spindle and feed it to the work by turning the tailstock handwheel.
For center drilling a workpiece, the combined drill and countersink is the most practical tool. These combined drills and countersinks vary in size and the drill points also vary. Sometimes a drill point on one end will be 1/8 inch in diameter, and the drill point on the opposite end will be 3/16 inch in diameter. The angle of the center drill must always be 60° so that the countersunk hole will fit the angle of the lathe center point. If a center drill is not available, center the work with a small twist drill. Let the drill enter the work a sufficient distance on each end; then follow with a 60° countersink.
In center drilling, use a drop or two of oil on the drill. Feed the drill slowly and carefully to prevent breaking the tip. Take extreme care when the work is heavy, because you will be less able to “feel” the proper feed of the work on the center drill.
If the center drill breaks during countersinking and part of the broken drill remains in the work, you must remove this part. Sometimes you can drive the broken piece out by a chisel or by jarring it loose, but it may stick so hard that you cannot remove it this way. Then you must anneal the broken part of the drill and drill it out.
We cannot overemphasize the importance of proper center holes in the work and a correct angle on the point of the lathe centers. To do an accurate job between centers on the lathe, you must ensure that the center-drilled holes are the proper size and depth and that the points of the lathe centers are true and accurate.
Figure —Examples of work mounted between centers.
MOUNTING THE WORK.—Figure shows correct and incorrect ways to mount work between centers. In the correct example, the driving dog is attached to the work and held rigidly by the setscrew. The tail of the dog rests in the slot of the faceplate, without touching the bottom of the slot. The tail extends beyond the base of the slot so that the work rests firmly on both the headstock center and the tailstock center. In the incorrect example, note that the tail of the dog rests on the bottom of the slot on the faceplate at A and pulls the work away from the center’s point, as shown at B and C. This causes the work to revolve eccentrically.
In mounting work between centers for machining, be sure there is no end play between the work and the dead center. However, do not have the work held too tightly by the tailstock center. If you do, as the work revolves, it will heat the center’s point, destroying both itself and the center. To help prevent overheating, lubricate the tailstock center with grease or oil.

Holding Work on a Mandrel
Many parts, such as bushings, gears, collars, and pulleys, require all the finished external surfaces to run true with their center hole, or bore.
General practice is to finish the bore to a standard size within the limit of the accuracy desired. Thus a 3/4-inch standard bore would have a finished diameter of from 0.7495 to 0.7505 inch This variation is due to a tolerance of 0.0005 inch below and above the true standard of exactly 0.750 inch. First drill the hole to within a few thousandths of an inch of the finished size; then remove the remainder of the material with a machine reamer, following with a hand reamer if the limits are extremely close.
Then press the piece on a mandrel tightly enough so the work will not slip while being machined Clamp a dog on the mandrel, which is mounted between centers. Since the mandrel surface runs true with respect to the lathe axis, the turned surfaces of the work on the mandrel will be true with respect to the bore of the piece. A mandrel is simply a round piece of steel of convenient length which has been center drilled and ground true with the center holes. Commercial mandrels are made of tool steel, hardened and ground with a slight taper (usually 0.0005 inch per inch). This taper allows the standard hole in the work to vary according to the usual shop practice and still provides a drive to the work when the mandrel is pressed into the hole. The taper is not great enough to distort the hole in the work The center-drilled centers of the mandrel are lapped for accuracy. The ends are turned smaller than the body of the mandrel and provided with flats, which give a driving surface for the lathe dog.
Holding Work in Chucks
The independent chuck and universal chuck are used more often than other work-holding devices in lathe operations. The universal chuck is used for holding relatively true cylindrical work when the time required to do the job is more important than the concentricity of the machined surface and the holding power of the chuck When the work is irregular in shape, must be accurately centered, or must be held securely for heavy feeds and depth of cuts, an independent chuck is used. FOUR- JAW INDEPENDENT CHUCK.-Figure shows a rough cylindrical casting mounted in a four-jaw independent lathe chuck on the spindle of the lathe. Before truing the work, determine which part you wish to have turned true. To mount this casting in the chuck, proceed as follows:
1. Adjust the chuck jaws to receive the casting. The same point on each jaw should touch the same ring on the face of the chuck If there are no
Figure —Work mounted in a four-jaw chuck.
rings, put each jaw the same distance from the outside edge of the body of the chuck.
2. Fasten the work in the chuck by turning the adjusting screw on jaw 1 and then on jaw 3, a pair of jaws which are opposite each other. Next, tighten jaws 2 and 4.
3. At this stage the work should be held in the jaws just tightly enough so it will not fall out of the chuck while you turn it.
4. Revolve the spindle slowly by hand and, with a piece of chalk, mark the high spot (A) on the work while it is revolving. Steady your hand on the tool post while holding the chalk.
5. Stop the spindle. Locate the high spot on the work and move the high spot toward the center of the chuck by releasing the jaw opposite the chalk mark and tightening the one nearest the mark
6. Sometimes the high spot on the work will be located between adjacent jaws. In that case, loosen the two opposite jaws and tighten the jaws adjacent to the high spot.
THREE-JAW UNIVERSAL CHUCK.—The three-jaw universal or scroll chuck is made so that all jaws move at the same time. A universal chuck will center almost exactly at the first clamping, but after a long period of use may develop inaccuracies of up to 0.010 inch in centering the work. You can usually correct the inaccuracy by inserting a piece of paper or thin shim stock between the jaw and the work on the high side.
When you chuck thin sections, be careful not to clamp the work too tightly because the work will distort. If you machine distorted work, the finished work will have as many high spots as there are jaws, and the turned surface will not be true.
Care of Chucks
To preserve the accuracy of a chuck, handle it carefully and keep it clean and free from grit.
NEVER force a chuck jaw by using a pipe as an extension on the chuck wrench.
Before mounting a chuck, remove the live center and fill the hole with a rag to prevent chips and dirt from getting into the tapered hole of the spindle. Clean and oil the threads of the chuck and the spindle nose. Dirt or chips on the threads will not allow the chuck to run true when it is screwed up to the shoulder. Screw the chuck on carefully, tightening it just enough to make it difficult to remove. Never use mechanical power to install a chuck.
To remove a chuck, place a spanner wrench on the collar of the chuck and strike a smart blow on the handle of the wrench with your hand. When you mount or remove a heavy chuck, lay a board across the bed ways to protect them; the board will support the chuck as you put it on or take it off.
The comments on mounting and removing chucks also apply to faceplates.
Holding Work on a Faceplate
A faceplate is used for mounting work that cannot be chucked or turned between centers because of its size or shape.
Work is secured to the faceplate by bolts, clamps, or any suitable clamping means. The holes and slots in the faceplate are used for anchoring the holding bolts. Angle plates may be used to position the work at the desired
Figure —Work clamped to an angle plate.
angle, as shown in figure . Note the counterweight added for balance.
For work to be mounted accurately on a faceplate, the surface of the work in contact with the faceplate must be accurately faced. It is good practice to place a piece of paper between the work and the faceplate to prevent slipping.
Before you clamp the work securely, move it about on the surface of the faceplate until the point to be machined is centered accurately with the axis of the lathe. Suppose you wish to bore a hole, the center of which has been laid out and marked with a prick punch. First, clamp the work to the approximate position on the faceplate. Slide the tailstock up until the dead center just touches the work. (NOTE: The dead center should have a sharp, true point.) Now revolve the work slowly; if the work is off center, the point will scribe a circle on the work. If the work is on center, the point of the dead center will coincide with the prick punch mark.

Using the Center Rest and Follower Rest
Place the center rest on the ways where it will give the greatest support to the workpiece. This is usually at about the middle of its length.
Figure —Work mounted in a chuck and center rest.
Ensure that the jaws of the center rest are adjusted to support the work while allowing it to turn freely. Figure shows how a chuck and center rest are used for machining the end of a workpiece.
The follower rest differs from the center rest in that it moves with the carriage and provides support against the forces of the cut only. Set the tool to the diameter selected, and turn a “spot” about 5/8 to 3/4 inch wide. Then adjust the follower rest jaws to the finished diameter to follow the tool along the entire length to be turned.
Use a thick oil on the center rest and follower rest to prevent “seizing” and scoring of the workpiece. Check the jaws frequently to see that they do not become hot. The jaws may expand slightly if they get hot, pushing the work out of alignment (when using the follower rest) or binding (when using the center rest).
Holding Work in a Draw-In Collet Chuck
The draw-in collet chuck is used for very fine, accurate work of small diameter. Long work can be passed through the hollow drawbar. Short work can be placed directly into the collet from the front. The collet is tightened on the work by rotating the drawbar to the right; this draws the collet into the tapered closing sleeve. The opposite operation releases the collet. Accurate results are obtained when the diameter of the work is exactly the same size as the dimension stamped on the collet. In some cases, the diameter may vary as much as 0.002 inch; that is, the work may be 0.001 inch smaller or larger than the collet size. If the work diameter varies more than this, it will impair the accuracy and efficiency of the collet. That is why a separate collet should be used for each small variation or work diameter, especially if precision is desired.
Figure .—Facing a cylindrical piece.

Figure —Facing a shoulder.
Up to this point, you have studied the preliminary steps leading to the performance of machine work in the lathe. You have learned how to mount the work and the tool and which tools are used for various purposes. Now, you need to consider how to use the proper tools in combination with the lathe to perform various machining operations.
Facing is the machining of the end surfaces and shoulders of a workpiece. In addition to squaring the ends of the work, facing provides a way to cut work to length accurately. Generally, only light cuts are required since the work will have been cut to approximate length or rough machined to the shoulder.
Figure shows the facing of a cylindrical piece. The work is placed between centers and driven by a dog. A right-hand side tool is used as shown. Take a light cut on the end of the work, feeding the tool (by hand crossfeed) from the center toward the outside. Take one or two light cuts to remove enough stock to true the work Then reverse the workpiece, install the dog on the just finished end, and face the other end to make the work the proper length. To provide an accurate base from which to measure, hold another rule or straightedge on the end you faced first. Be sure there is no burr on the edge to keep the straightedge from bearing accurately on the finished end. Use a sharp scribe to mark off the dimension desired. Figure shows the use of a turning tool in finishing a shouldered job having a fillet corner. Take a finish cut on the small diameter. Machine the fillet with a light cut. Then use the tool to face the work from the fillet to the outside of the work.
In facing large surfaces, lock the carriage in position, since only crossfeed is required to traverse the tool across the work. With the compound rest set at 90° (parallel to the axis of the lathe), you can use the micrometer collar to feed the tool to the proper depth of cut.
Turning is the machining of excess stock from the periphery of the workpiece to reduce the diameter. In most lathe machining operations requiring removal of large amounts of stock, a series of roughing cuts is taken to remove most of the excess stock Then a finishing cut is taken to accurately “size” the workpiece.
Rough Turning
When a great deal of stock is to be removed, you should take heavy cuts to complete the job in the least possible time. This is called rough turning. Select the proper tool for taking a heavy chip. The speed of the work and the amount of feed of the tool should be as great as the tool will stand.
When you take a roughing cut on steel, cast iron, or any other metal that has a scale on its surface, be sure to set the tool deep enough to get under the scale in the first cut. Unless you do, the scale on the metal will dull or break the point of the tool.
Rough machine the work to almost the finished size; then take careful measurements.
Bear in mind that the diameter of the work being turned is reduced by an amount equal to twice the depth of the cuts; thus, if you desire to reduce the diameter of a piece by 1/4 inch, you must remove 1/8 inch of metal from the surface.
Figure shows the position of the tool for taking a heavy cut on large work. Set the tool so that if anything
Figure —Position of the tool for a heavy cut.
Figure —Machining to a shoulder.
occurs during machining to change the position of the tool, it will not dig into the work, but rather will move in the direction of the arrow-away from the work
Finish Turning
When you have rough turned the work to within about 1/32 inch of the finished size, take a finishing cut. A fine feed, the proper lubricant, and, above all, a keen-edged tool are necessary to produce a smooth finish. Measure carefully to be sure you are machining the work to the proper dimension. Stop the lathe when you take measurements.
If you must finish the work to close tolerances, be sure the work is not hot when you take the finish cut. If you turn the workpiece to exact size when it is hot, it will be undersize when it has cooled.
Perhaps the most difficult operation for a beginner in machine work is to make accurate measurements. So much depends on the accuracy of the work that you should make every effort to become proficient in the use of measuring instruments. You will develop a certain “feel” in the application of micrometers through experience alone; do not be discouraged if your first efforts do not produce perfect results. Practice taking micrometer measurements on pieces of known dimensions. You will acquire skill if you are persistent.
Turning to a Shoulder
Machining to a shoulder is often done by locating the shoulder with a parting tool. Insert the parting tool about 1/32 inch from the shoulder line toward the small diameter end of the work Cut to a depth 1/32 inch larger than the small diameter of the work. Then machine the stock by taking heavy chips up to the shoulder. This procedure eliminates detailed measuring and speeds up production.
Figure illustrates this method of shouldering. A parting tool has been used at P and the turning tool is taking a chip. It will be unnecessary to waste any time in taking measurements. You can devote your time to rough machining until the necessary stock is removed. Then you can take a finishing cut to accurate measurement.
Boring is the machining of holes or any interior cylindrical surface. The piece to be bored must have a drilled or cored hole, and the hole must be large enough to insert the tool. The boring process merely enlarges the hole to the desired size or shape. The advantage of boring is that a true round hole is obtained, and two or more holes of the same or different diameters may be bored at one setting, thus ensuring absolute alignment of the axis of the holes.
Work to be bored may be held in a chuck, bolted to the faceplate, or bolted to the carriage. Long pieces must be supported at the free end in a center rest. When the boring tool is fed into the hole of work being rotated on a chuck or faceplate, the process is called single point boring. It is the same as turning except that the cutting chip is taken from the inside. The cutting edge of the boring tool resembles that of a turning tool. Boring tools may be the solid forged type or the inserted cutter bit type.
When the work to be bored is clamped to the top of the carriage, a boring bar is held between centers and driven by a dog. The work is fed to the tool by the automatic longitudinal feed of the carriage. Three types of boring bars are shown in figure. Note the center holes at the ends to fit the lathe centers.
Figure, view A, shows a boring bar fitted with a fly cutter held by a headless setscrew. The other setscrew, bearing on the end of the cutter, is for adjusting the cutter to the work
Figure, view B, shows a boring bar fitted with a two-edged cutter held by a taper key. This is more of a finishing or sizing cutter, as it cuts on both sides and is used for production work.
The boring bar shown in figure, view C, is fitted with a cast-iron head to adapt it for boring work
Figure –Boring bars.
Figure –Tapers.
of large diameter. The head is fitted with a fly cutter similar to the one shown in view A of figure . The setscrew with the tapered point adjusts the cutter to the work
Although you will probably have little need to machine tapers, we have provided the following explanation for your basic knowledge.
A taper is the gradual decrease in the diameter of a piece of work toward one end. The amount of taper in any given length of work is found by subtracting the size of the small end from the size of the large end. Taper is usually expressed as the amount of taper per foot of length or taper per inch of length. We will take two examples.
Example l.–Find the taper per foot of a piece of work 2 inches long. The diameter of the small end is 1 inch; the diameter of the large end is 2 inches.
The amount of taper is 2 inches minus 1 inch, which equals 1 inch. The length of the taper is given as 2 inches. Therefore, the taper is 1 inch in 2 inches of length. In 12 inches of length the taper is 6 inches. (See fig. 9-31.) Example 2.–Find the taper per foot of a piece 6 inches long. The diameter of the small end is 1 inch; the diameter of the large end is 2 inches. The amount of taper is the same as in example 1, that is, 1 inch. However, the length of this taper is 6 inches; hence the taper per foot is 1 inch times 12/6, which equals 2 inches per foot .
In machining operations, always keep safety in mind, no matter how important the job is or how well you know the machine you are operating.
Listed here are some safety precautions that you MUST follow:
1. Before starting any lathe operations, always prepare yourself by rolling up your shirt sleeves and removing your watch, rings, and other jewelry that might become caught while you operate the machine.
2. Wear goggles or an approved face shield at all times whenever you operate a lathe or when you are near a lathe that is being operated.
3. Be sure the work area is clear of obstructions that you might fall or trip over.
4. Keep the deck area around your machine clear of oil or grease to prevent the possibility of slipping or falling into the machine.
5. Always use assistance when handling large workpieces or large chucks.
6. NEVER remove chips with your bare hands. Use a stick or brush, and always stop the machine.
7. Always secure power to the machine when you take measurements or make adjustments to the chuck.
8. Be attentive, not only to the operation of your machine, but also to events going on around it. NEVER permit skylarking in the area.
9. Should it become necessary to operate the lathe while the ship is underway, be especially safety conscious. (Machines should be operated ONLY in relatively calm seas.)
10. Be alert to the location of the cutting tool while you take measurements or make adjustments.
11. Always observe the specific safety precautions posted for the machine you are operating.
In this chapter, you have learned the principal parts, the attachments and accessories, the uses and the basic operation of the engine lathe. Additionally, you have learned the basic operational safety precautions.

Lathe: Work Centering The Mechanic Tools

Lathe: Work Centeringthe Mechanic


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Lathe: Work Centering The Mechanic Training

MARVELOUS accomplishments in the mechanical world have become so common in this day and age that we scarcely realize the slow process of evolution which machine shop work has been undergoing during th...
Part I. Hand-Operated Tools
Simultaneous Use of Hand Tools and Machines. Machine shop work is usually understood to include all cold metal work in which a portion of the metal is removed to make the piece of the required shape a...
Measuring Tools
Angular Measurement Surface Gage The surface gage is used in laying out work for the bench, lathe, or planer. The ordinary form consists of a heavy base, an upright which is firmly attached to t...
Measuring Tools. Part 2
Keyseat Rule For drawing lines and laying off distances on curved surfaces, such as shafts, a combination of two straightedges, or a straightedge and a rule, is used. This is often called a keyseat...
Measuring Tools. Part 3
Protractor The bevel can be adjusted only by direct application to lines or surfaces having the proper angular relation. It often happens that such adjustment is not feasible and, therefore, a regi...
Measuring Tools. Part 4
Dividers For transferring and comparing distances, dividers are commonly used. They are classified according to the style of joint and the length of the leg. The most simple joint is the friction a...
Outside and Inside Calipers. Instead of having straight legs with sharp points, caliper legs are bent and have blunt points. As distances are to be measured both outside and inside of solid bodies, we...
For measurements which are required to be more accurate than can be obtained by the preceding forms of calipering devices, the micrometer caliper, Fig. 20, is used. The accuracy of its measurements is...
Micrometers. Continued
Reading the Micrometer Reading in thousandths. As stated, the micrometer screw has usually forty threads per inch and the thimble has twenty-five divisions on its circumference. The barrel is divid...
Vernier Calipers
A common use of a Vernier is its application to a caliper square, termed a Vernier caliper. Fig. 24 shows a representative tool. How to Read the Vernier The following text represents the L. S. S...
Fixed Gages
While the adjustable tools just described are available for a large range of work, gages of one dimension, or fixed gages, are used to a considerable extent, especially in shops where work of a duplic...
Surface Plates
For the production of accurate plane surfaces the use of the straightedge is not sufficient. Such surfaces should be compared with standard surfaces, called surface plates, Fig. 41. A surface plate is...
Work Vises
In order that work may be held rigidly for the performance of hand operations, the machinist uses what is termed a vise. They are made in a great variety of forms and sizes, but all consists essential...
Classification The machinist uses hammers of three shapes: ball peen, cross peen, and straight peen, Fig. 45. The ball peen is the most common; it varies in weight from 4 ounces to 3 pounds. The cr...
Cutting Tools. Chisels
The simplest form of metal-cutting tool is the chisel. The several types in common use are shown in Fig. 46. Flat Chisel The flat chisel is used for snagging castings, for chipping surfaces havi...
Chipping is a term applied to the removal of metal with the cold chisel and hammer. The degree of accuracy required varies. The piece is held in a vise, and the method of working is to grasp the chise...
Characteristics The file differs from the chisel in having a large number of cutting points instead of one cutting edge and in being driven directly by the hand instead of by the hammer. As hand po...
Files. Part 2
File Handles The handles commonly attached to files are of wood and are made to fit the hollow of the hand. The handle is driven onto the tang of the file, a ferrule on the handle preventing it fro...
Files. Part 3
Cleaning File The particles of metal removed by a file frequently remain in the teeth and diminish their cutting qualities. In the case of hard metals, these particles, or pins, often scratch the...
Files. Part 4
Hand Scraping When two flat or curved surfaces are to be worked together, and close contact over the surfaces of both is desired, they are hand scraped. Scraping removes less metal than filing and ...
Files. Part 5
Scratch Awl The scriber or scratch awl, Fig. 61, is made in many forms, but consists essentially of a cast-steel rod about 8 inches long and 3/16 inch diameter, with a long, slender, hardened point...
Drilling is the term used by shop men to denote hole production by means of a rotating tool which is provided with cutting edges located at its point. The drill, therefore, is an end cutting tool as d...
Care of Drills
Lubrication of Drills When drilling tough metals, such as steel and wrought and malleable iron, heat is generated by the bending or changing of the form of the metal being removed and by friction c...
Care of Drills. Continued
Resharpening Drills Great care should be exercised in the resharpening of drills. The cone point of a drill should be symmetrical, that is, the lips should be of the same length and form the same a...
Use of Reamers It is difficult, if not quite impossible, to drill a hole to an exact standard diameter. For much work, a variation of a few thousandths of an inch from the nominal diameter is of no...
Reamers. Continued
Taper Reamers Reamers are made for tapered as well as for straight holes. The angle varies with the intended use of the taper. For example, the locomotive taper of 1/16 inch per foot is intended fo...
Hand Threading Tools. Taps
Types of Taps When internal thread cutting is done by hand, the tool used is called a tap. There are many styles of taps, the Fig. 81. Types of Hand Taps: Left-Taper Tap; Center-Plug...
Hand Threading Tools. Taps. Continued
Hand Tapping The cutting of a thread with a tap is not a difficult operation but requires care in the manipulation. The tap does not need to be forced into the work, since the thread will draw it f...
Threading Dies
Dies are used for cutting threads on bolts and other similar parts to be placed in holes which have been threaded by taps. The general rules given for the use of taps apply to dies. As the number of t...
Cutting Pipe Threads
Another common form of thread cutting is that on wrought-iron pipe. The pipe thread is rounded slightly at top and bottom and is made tapering at the rate of three-quarters of an inch per foot. The di...
Part II. Power-Driven Tools
Lathes Origin The lathe is undoubtedly the oldest form of machine tool. Its prototype is the drilling machine. Each of these machine tools probably developed from that earliest example of mechan...
Part II. Power-Driven Tools. Part 2
Round Nose The round nose is used solely for turning concave surfaces, being held as high on the work as proper cutting will allow, as shown in Fig. 93. Slide Rest To make the hand lathe more...
Part II. Power-Driven Tools. Part 3
Work Spindle Arrangement The work spindle projects through the bearings at each end. At the right it is usually threaded to receive a faceplate F, and is also bored out and tapered for a work cente...
Lathe Equipment
Setting Up Change-Gears for Thread-Cutting. The descriptions in the preceding pages apply particularly to the usual form of engine lathe, and a clear understanding of its construction and the details ...
When the proper ratio cannot be obtained by the use of the change-gears at hand, or when the gears of the desired numbers of teeth would be too small to connect properly, or too large to put in place,...
Rapid Change-Gear Devices
The more recent development of the thread-cutting mechanism of engine lathes aims to arrange the change-gears so that any desired thread may be cut without removing or replacing any of the gears. To a...
Lathe Attachments
The attachments usually furnished without extra charge are a large faceplate of the full swing of the lathe, a center rest, and a follower rest. The small faceplate is used only for driving the work i...
The lathe chuck, Fig. 103, consists of a body which is fastened to a special faceplate in such a way that it is concentric with the spindle. The three jaws AAA can be moved in and out toward or from t...
Another method of holding work is by the use of a mandrel. This is a piece of steel with a slight taper; the ends are flattened for the lathe dog, as shown in Fig. 109. It frequently happens that a pi...
Cutting Tools
General Characteristics The cutting tools used in lathes are of a great variety of shapes. These shapes are adapted to the work that is to be done, and to the kind of finish that is to be left upon...
Clearance prevents the tool from rubbing on the work, while rake adds to the keenness of the cutting edge, and gives freedom to the removal of the chips. A tool should have sufficient strength at the ...
The tool is usually held to the carriage by means of a tool-post, shown in Fig. 118. The post consists of a piece with a slotted hole through the center for the tool B. A ring C slips over the post an...
Diamond Point
A common form of tool for turning wrought iron and steel is the diamond point, shown in Fig. 124. The name is derived from the shape of the top face. This tool has both front and side rake, which form...
Cutting-Off or Parting Tool
This tool is illustrated in Fig. 127. The blade is quite narrow-as narrow, in fact, as the character of the work will allow. As the blade needs to be narrower at the shank and at the bottom than it is...
Boring Tools
The term boring as used in machine practice usually means methods of machining internal surfaces, other than those of common drilling and reaming. Also methods for holding the work other than those co...
Cutting Speed
Importance of Speed Element. The speed at which cutting is done is an important matter. This varies with the shape of the tool, the quality of the metal being worked, and the strength of the lathe. Th...
Speeds for High-Speed Steel
The cutting speeds given above are what may be used with the best grades of tool steel, such as Jessop's; but by using air-hardening or tungsten steels, the speed of cutting may be very much increased...
Cooling the Tools
For cooling the tool while performing heavy duty, a solution of sal soda is preferable to water, as it prevents rusting of the work and machinery. Its office is simply to keep the tool cool. If a tool...
Lathe Operations. Mounting Work on Lathe. Centering Method
A piece to be turned is supported on the two centers of the lathe. In order that this may be done, it is prepared by drilling and countersinking a hole in each end. This is called centering the work. ...
Adjusting Pieces to Center on Faceplate
Whenever a piece is to be turned on a lathe faceplate, it is necessary to adjust it so that its rough outline is approximately concentric with the lathe centers. This is done by bolting it lightly to ...
Centering Finished Work
After making the center punch mark in the end of the piece, it is drilled and countersunk. This must be done very accurately, but frequently the drilled hole or the countersink will not be in the exac...
Facing or Squaring Up. The first operation usually performed on a piece of work when placed in the lathe is facing or squaring up the ends. This must be done to get a uniform bearing for the centers. ...
Setting over Dead Center
Setting the dead center over is the more common method. Provision is generally made for moving the dead center laterally toward the front or rear of the bed according to the taper required. With the d...
Compound Slide
In turning a taper with the compound slide, the work may be held in a chuck, on the faceplate, or between the centers. The compound slide, Fig. 146, is then set at such an angle that the direction of ...
Turning Shafting
Shafting is usually turned 1/16 inch less than the nominal diameter. For instance, instead of a shaft 2 inches in diameter, one of 1 15/16 inches in diameter is used. The reason is that iron of a nomi...
Eccentric Turning
The term eccentric is given to a rotating machine part which is used to throw a mechanism eccentric with its main center line. Eccentrics may be said to include all crank motions, also many cam mo...
Crank-Shaft Turning
This is a special kind of eccentric turning in which the throws are termed crank pins and the remaining bearings are the shaft proper. In Fig. 148 is shown a simple crank shaft with a crank pin G and ...
Boring Bars
The boring of holes sometimes calls for a length and strength of tool that cannot be readily attained with the ordinary boring tool. A great deal of such boring is done with double-headed tools. These...
Screw Cutting
The tools used for cutting threads are called screw-cutting tools. These tools are used in the lathe in the same manner as the diamond-point and round-nosed tools. The cutting edge of the tool must be...
Cutting Tool for Square Threads
The tool used for cutting square threads is shown in Figs. 158 and 159. It is of the proper Table III* U. S. Standard Threads, Bolts, And Nuts The Tap Drill Diameters in the Table Provide for a ...
Cutting Standard Screw-Threads
When screw-threads are to be cut, the pitch used depends upon the outside diameter of the bar. A standard which has been generally adopted in the United States, is known as the United States Standard....
Lathe Adjustment for Cutting Threads
The cutting of a thread demands that there shall be a certain definite ratio of motion between the rotation of the work and the travel of the carriage. For example, if a screw having a pitch of 1/4 in...
Selecting the Gears
The rule for finding the gears to be used on the spindle and lead-screw is: Multiply the number of threads on the lead-screw and the number of threads to be cut, by the same number; the products will ...
Compounding Gears
It is sometimes necessary to cut a screw for which there are no gears which make a direct connection, in which case the simple gearing shown in Fig. 164 cannot be used. This necessitates the compoundi...
The ordinary methods of cutting screws have already been described. Where great accuracy is not necessary, the threads may be chased by hand. A chaser, or chasing tool, differs from the ordinary threa...
Drilling in the Lathe
The lathe can also be used for drilling. When such Work is to be done, the drill may be held in the spindle, and the work forced up against it by the screw of the tailstock; or the work may be revolve...
Drilling Operation Where holes are to be cut through metal using a rotating tool with the cutting edges at its point, the operation is known as drilling and the cutting tools are termed drills. The...
Power Feed Driller
The heavier types of these machines are usually provided with back gearing similar to that employed in engine lathes. The power feed is obtained by suitable spindles and trains of gearing which drive ...
Radial Driller
Another form of driller, known as the radial, is being extensively used. It is shown in Fig. 177. The drill spindle is carried on the horizontal arm, and is arranged to be set and run at any position ...
Holding the Work
A matter to receive due consideration is that the work must be held rigidly on the work table while being drilled. This may be done in two ways. If the holes are to be drilled with great accuracy, the...
As the name indicates, the planer is used for finishing flat surfaces. In the ordinary planer, the work is moved, and the tool is at rest. A common form of this tool is shown in Fig. 183. It consists ...
Planers. Continued
Planer Tools The tools used with planers do not differ essentially from those described for lathe work. The same rules apply regarding the holding of the tool. It should project as short a distance...
Plate Planer
A special form of planer extensively used in boiler shops and shipyards is the plate planer, Fig. 191. It is used for planing the edges of long plates. The plate is securely fastened between the 12 pn...
For the lighter jobs of planing, the shaper, or shaping planer, Fig. 192, is extensively used. It possesses the advantage of rapidity of action. In this machine, as in the plate planer, the tool recip...
Another machine tool which is not used as commonly as its many good qualities would seem to warrant, is the slotter, Fig. 194. It is in reality a shaper with the tool reciprocating vertically instead ...
Milling Machines
Milling Machine Vs Shaper and Planer. The operation known as milling differs so radically from the removal of metal by methods previously described, that it merits much more careful and lengthy dis...
Milling Cutters
Classification As the type of cutter used determines, in a large measure, the design of the machine itself, it will be better at this point to take up a description of some of the different cutters...
Cutter Arbor
Fig. 202 shows the usual form of cutter arbor, in which A is the taper shank fitting the taper-reamed hole in the milling-machine spindle; B is the flattened portion or tang fitting in the cross-slot ...
Plain Milling Cutters
Screw-slotting cutters, Fig. 203, and slitting saws, Fig. 204, are saws of a special type. The true milling cutter, Fig. 205, has a face much wider in proportion to its diameter than the common slitti...
Form Cutters
Brief mention has been made of cutters to generate irregular contours. These cutters are known as form cutters, and, except in certain shapes, such as quarter- and half-rounds, are not carried in stoc...
End Mills
All the cutters thus far mentioned are provided with central holes, and are intended to be mounted on an arbor which is carried by the milling machine spindle and supported in some suitable manner at ...
Dovetail Cutters
Dovetail cutters, Fig. 217, and cutters of various angles for making ratchets, are merely variations of the end mill When end mills are made of large size, they can be furnished with inserted teeth...
Types Of Milling Machines. Bench Miller
In taking up the subject of machines devoted especially to milling, it is well to consider that the transition from milling in the lathe to the special milling machine was bridged by an attachment to ...
Micrometer Graduations
It will be seen, therefore, that one of the principal advantages of the milling machine is its wide range of working capacity, and the accuracy with which the table can be placed with relation to the ...
Planer Type Milling Machines
The slabbing miller, Fig. 225, is of the planer type, the cross-rail carrying a rigidly supported cutter, while the table has the comparatively slow feed required for milling. This type of machine is ...
Milling Operations
Classification These may be classified in a manner similar to the cutters themselves, whose names will suggest the kind of work for which they are adapted. Plane Milling or Surface Milling Th...
Preparing the Milling Machine for Work
The taper shank of the arbor and the hole in the spindle should be wiped clean and free from oil or grit. Should the outer end of the arbor be supported by a pointed center or a bushing, it will not b...
Cutting Speeds
Conditions Governing Speed There are no hard and fast rules that will properly govern a majority of cases of the continually varying conditions of milling cutters, machines, and the material to be ...
Cutting Speeds. Part 2
Table IV. Speeds And Feeds For Milling Cutters Material Speed (ft. per min.) Feed (in. per min.) Soft cast iron 60 1 1/2 ...
Cutting Speeds. Part 3
Table V. Surface Milling Of Cast Iron Diameter of Mill (in.) Revolutions per Minute Speed of Cutter per Minute (ft.) Depth of Cut (in.) ...
Cutting Speeds. Part 4
Table VII. End Or Face Milling Of Cast Iron Diameter of Mill (in.) Revolutions per Minute Speed of Cutter per Minute (ft.) Depth of Cut (in....
Cutting Speeds. Part 4. Part 2
Fig. 237. Fluting Taper Reamor. Courtesy of Van Norman Machine Tool Company, Springfield, Massachusetts Fig. 238. Milling Spirals with Table at Angle. Construct a right-angled triangl...
Cutting Speeds. Part 4. Part 3
Use of Dividing Head. In order that the gear may be accurately and quickly set for cutting each tooth, a dividing head is used, which is shown in Fig. 243. The mandrel upon which the gear blank is mou...
Grinding Machine
Value of Grinding as Finishing Process. When greater accuracy than that obtainable on the milling machine or the lathe is required, recourse is had to grinding. This operation depends upon the abrasiv...
Grinding Machine. Continued
Table IX. Speed Of Grinding Wheels Diameter of Wheel (in.) Maximum Revolutions PER MlNUTE Diameter of...
Lapping Holes Lapping is a term applied to a particular method employed in the grinding out of holes. The lap consists of a cylinder of soft metal run rapidly inside the hole to be lapped, and cove...
Disc Grinder for Flat Top Work
Laps for flat surfaces have grown in favor so rapidly that special machines called disc grinders have been made to do this work. The construction of the disc grinder can be so readily seen from the il...
Laying Out Work
Laying out work is one of the most important details of machine shop practice. Ordinarily all work is laid out. The exceptions are where certain pieces are worked from templets, and in these cases the...
Layout for Planer and Milling Machine
In laying out the work for the planer and milling machine, great care must be exercised. It is necessary that there should be a base line to which the lines may be referred. It depends on the chara...
Layout for Lathe
Work is rarely laid out for the lathe. It is not necessary that it should always be done for the planer. Laying out is employed where accuracy is essential, and where it is possible to secure the prop...
Fitting is the term generally applied to the hand work necessary in assembling machinery after all the machine work has been done. Filing, either in the vise or lathe, and scraping, are the. operation...
Peening consists in stretching the metal on one side of a piece of work in order to alter its shape. There is a wide difference between peening and bending. For example, suppose the curved or warped p...
Drilling Hard Metals
It is sometimes desirable to drill a hole in very hard metal. To do this the drill must be made very hard; it must be run at a very slow speed; it must be forced against the work as hard as possible w...
Generating Surface Plates
In this operation it is necessary to work with three at the same time. For the sake of making the explanation clear, they will be called A, B, and C. After the plates have been planed, a straightedge ...
Where a gas or liquid is to be retained in a pipe or other vessel without leakage, a tight joint is necessary. The method of grinding valves to their seats has already been explained. In that case, it...
Fluting Rollers
Where feed rollers such as those used in woodworking machinery are to be turned and fluted, the turning should always be done first. This insures a continuous surface for the cutting tool. Where old r...
Where castings are to be worked, either in the lathe or planer, to dimensions only a little less than those when rough, they should be pickled. This consists in washing them with a solution of sulphur...
Lining Shafting
In equipping a shop, the first work of the machinist is the erection of the shafting. The main line should be the first laid out; and the engine, together with the jack and counter-shafting, must be l...
Machine Setting
After the shafting is erected, comes the setting of machines. The countershafts are first erected parallel to the main line, and with due regard to the location of the machine. The machine is then pla...
The shafting and machines are usually driven by belting. Leather is the material generally used, and the belting may be from single to six-ply in any suitable width. Single belting has a flesh and a g...
Part IV. Gear Cutting
Theory of Toothed Gearing. The fundamental principle of toothed gearing is that of two cylinders or portions of cones with their surfaces in contact, and rolling together in opposite directions. Th...
Designing Gears
Fixed Pitch Method Formerly the teeth of gears were designed on the basis of a fixed distance representing the pitch. This was usually based on the common fractions of an inch or multiples of them,...
Laying Out Teeth
The method of laying out teeth of the first class is shown in Fig. 264. The pitch circle A has its center at B, upon the vertical line BC, From this center the addendum circle D and the dedendum or ro...
Internal Gears
Internal gears must frequently be used when there is not room for spur gears or when the nature of the work or the design of the machine of which they are a part renders this form necessary or advisab...
Teeth of Racks
Two methods are in use for drawing the form of teeth for racks. The first method is shown in Fig. 268. The pitch line A, addendum line B, and dedendum line C are straight lines located as before descr...
Bevel Gears
In the treatment of spur gears, we have considered them fundamentally as cylinders rolling upon each other (ordinary spur gears) or a cylinder rolling on the inner surface of a larger one (internal ge...
Worm Gearing
This is a term used to describe the device consisting of a gear similar to a spur gear driven by a worm-that is, a cylinder upon whose surface is a thread fitting into the teeth of the gear. The relat...
Spiral Gears
As has heretofore been stated, the spur gear has its teeth cut in a line parallel to the axis. If the teeth are cut at an angle to the axis, and the cut continued by the gradual rotation of the gear b...
Milling Process
The first process, milling with a properly formed revolving cutter, as in ordinary milling machine work, is applicable not only to the work mentioned above, but also to the cutting of spiral gears and...
Planing Process
First Method The second process, that of planing the forms of the teeth, is accomplished by three methods. One is to form a planing tool to the exact contour of the space between the teeth, and by ...
Hobbing Gears
In forming the teeth of worm gears, the greater part of the space is cut out by a stocking cutter or roughing cutter, which is adjusted at a proper angle, according to the pitch of the worm which the ...
Tools for Testing Gear Teeth
To ascertain if the teeth of a gear are being cut properly, the gear-tooth caliper shown in Fig. 280 is used. This is for measuring the distance from the top of the teeth to the pitch line, and the th...
Cutting Spiral Gears
In cutting spiral gears the universal milling machine is generally used, as it is provided with proper devices for rotating the gear blank at the same time that it is fed toward the cutter. The machin...
Cutting Spiral Gears. Part 2
Automatic Gear-Cutting Machine The automatic gear-cutting machine built by Gould and Eberhardt is shown in Fig. 285. It is of the same type as that built by Brown and Sharpe and possesses some exce...
Cutting Spiral Gears. Part 3
Bilgram Gear-Planing Machine The Bilgram gear-planing machine, shown in Fig. 290, operates upon a principle similar to that of the machine just described, but with this important difference. In the...
Turret Lathes
The turret lathe, as we know it today, is a comparatively modern machine, and was developed from an ordinary engine lathe by the addition of revolving tool-holding devices called turrets. The turre...
Turret Lathes. Part 2
Fig. 292. Form of Monitor Lathe. An engine lathe equipped as described in class 1 is shown in Fig. 293. In this particular machine, the turret is of hexagona form. In the earlier machines it wa...
Turret Lathes. Part 3
Fig. 297. I 24-Inch Turret Lathe with Motor Drive Courtesy of Gisholt Machine Company, Madison, Wisconsin. A very complete turret lathe is shown in Fig. 297, as an example of class 5. The tur...
Tools for the Turret
Drills, reamers, boring bars, counter-bores, etc., may have shanks formed upon them, or may fit in collets fitted to the tool-holes in the turret, or in plain drill-holders. A split collet is shown in...
Turret-Lathe Operations
The particular sphere of the turret lathe, and the use of the various tools and tool-holding devices, can be best explained by illustrating and describing some of the more important operations in the ...
Turret-Lathe Operations. Continued
First Operation The wheel is chucked as shown at A on the inside of the rim, by the chuck-jaws B, This leaves the outside of the rim clear for the turning tools. The cored hole is first rough-bored...
Automatic Screw Machines
The automatic screw machine, in its design and method of operation, is a highly developed type of turret lathe, its cutting tools being carried in some form of turret. By the term turret, as used in t...
Types of Automatic Screw Machines
Manufacturing Auto-Matic Chucking And Turning Machine Fig. 313 shows a Potter and Johnson machine, called by them a manufacturing automatic chucking and turning machine. It is a good example of a s...
Cleveland Automatic Machine
Fig. 315 shows a Cleveland automatic machine, of which several variations of the same style are built. The main spindle A is driven from the system of pulleys B, the belt being controlled by the autom...
Brown and Sharpe Automatic Screw Machine
This machine, shown in Fig. 318, is of a type quite distinct from any of those above described. It will be noticed that the machine is very compact when compared with some of the others previously ill...
Brown and Sharpe Automatic Screw Machine. Continued
Setting-Up the Machine A variety of types of automatic screw machines have been shown and described, in order that the reader may familiarize himself with those built by different manufacturers, an...
Part V. Modern Manufacturing
Machine Building Vs Machine Manufacturing. While machine work in general, and the use of machine tools in particular are much the same in all shops, the methods employed in machine building and in ...
Part V. Modern Manufacturing. Part 2
Specialized Cutting Steels Modern investigations have led to the adoption of specialized cutting methods and cutting tools in up-to-date manufacturing. At the very center of these shop efficiency m...
Part V. Modern Manufacturing. Part 3
Special Die Forgings While the ordinary forged piece is seldom suited for use in accurate machine construction without previous machining, several firms are now producing special die forged machine...
Belt Drives The belt manufacturer has helped to solve this problem by producing belting suited to the machine constructor's needs. Most conditions of temperature, humidity, and pliability have been...
Grinding Machines
Range of Usefulness While in many shops the grinding machine is used only as a finishing tool on parts which require a special surface, or in which greater accuracy is required than is readily reac...
Grinding Machines. Continued
Wheel Traverse This is taken as the distance the abrasive wheel travels axially during a complete revolution of the work. While experts differ as to what proportion of the face of the wheel this sh...
Grinding Methods
Skilled Operators The larger manufacturers of grinding machines have representatives trained to the highest skill in operating their line of machines. A purchaser of their machines can have one of ...
Internal Cylindrical Grinding
Machine grinding the internal surfaces of gas engine cylinders may be used as a good example of this line of production work. Figs. 334 and 335 show two views of such work. It will be noted that these...
Internal Cylindrical Grinding. Part 2
Table XIV-(Continued) Selection Of Grades Class of Work Alundum Crystolon Grain Grade Grain Grade ...
Internal Cylindrical Grinding. Part 3
Table XV. Rate Of Grinding Gun Parts On Vertical Grinder No 1 on two sides - 40 to 50 per hour No. 2 on one side - ...
Milling Machines: Horizontal, Vertical and Planer
Production milling is done on three distinct types of machines known as the horizontal, the vertical, and the planer type. Horizontal Milling Machine Fig. 341 shows a representative machine of t...
Drilling Machines
Production drilling machines are of two sorts: Those designed for heavy drilling, and those for the lighter jobs. Fig. 347. Ingersoll Horizontal Miller Doing Heavy Milling Note how lubricant fl...
Drilling Machines. Continued
Table XVII. High-Speed Drills Size of Drill (in.) Feed per Rev. (in.) Bronze Brass r.p.m. 300 FT. C.Iron Ann'ld r.p.m. 170 FT. ...
Turning Machines
Special and specialized machines for high speed turning will be illustrated under this heading. Turning Lathe Fig. 351 shows a production lathe for rapid turning of machine parts. It is represen...
Planing Machines
Production Planers The machine tool shown in Fig. 363 is for quantity production of plane surfaces. Enormous machines of this type are in use, constructed to drive and feed the best of cutting tool...
Broaching Machines
Types of Machines and Nature of Work. Fig. 365 is representative of a type of machine tool which makes use of a train of cutting edges for roughing and finishing holes in machine parts. Typical broach...
Production Tools, Jigs, And Fixtures. Cutting Tools
Materials Iron. Iron is one of the commonest metals in use. In nature it is found in a form known as iron ore. In this form it has many impurities from which it must be separated before it is valua...
Jigs And Fixtures
General Classification The terms jigs and fixtures are rather loosely used by shopmen. While this is necessarily so in some cases, in most instances it is more correct to apply the term jig to ...
Jigs And Fixtures. Part 2
Table XIX. Dimensions Of Stationary Drill Bushings A B L 1/16 3/16 3/8 1/8 1/4 ...
Jigs And Fixtures. Part 3
Table XX. Dimensions Of Lining Bushings A B L 5/16 l/2 1/2 3/8 9/16 1/2 ...
Jigs And Fixtures. Part 4
Table XXI. Dimensions Of Removable Drill Bushings A B c D E F H I K 1/8 ...
Jigs And Fixtures. Part 5
Table XXII. Bushings For Holes Reamed With Rose Chucking Reamers A B C D E F G H I ...
Jigs And Fixtures. Part 6
Spotting Hand scraped or other plane surfaces are given an attractive appearance by what is termed spotting. A skilful worker with the hand scraper will cover a plane surface with regular spots i...
Boring Fixtures
Fig. 391 shows a fixture used in boring out the head casting of a ball-bearing lathe. In this fixture, the casting is held while being bored. As the spindle holes are located by the bushed holes for t...
Ball Bearings
Uses of Ball Bearings. The claims made for the use of ball bearings in preference to plain bearings are several in number as follows: Less wear, less frictional resistance, more compact, non-heating i...
Ball Bearings. Part 2
Extra Heavy Type 17 0.6693 62 2.4409 20 0.7874 1,100 880 680 540 20...
Ball Bearings. Part 3
Heavy Type 17 0.669 62 2.441 17 0.669 750 600 450 370 20 ...
Ball Bearings. Part 4
Table XXIII. (Continued) Load Capacities Of Radial Ball Bearings Diameter Bore Outside Diameter Width Revolutions per Minute Millimet...
Ball Bearings. Part 5
Light Type 10 0.393 30 1.181 9 0.354 220 175 120 108 12 ...
Ball Bearings. Part 6
Table XXIV. Loads For Thrust Collar Bearings No. OF Balls Size of Balls Revolutions per Minute 1500 1000 500 ...
Ball Bearings. Part 7
Light Weight, Load In Pounds 21 5/16 640 770 900 1,155 1,410 1,630 2,200 2,970 ...
Magnetic Chucks
Uses in Production Work. A magnetic chuck is essentially an electromagnet provided with a flat work face. Fig. 397 shows a magnetic chuck of the type commonly used on planers, milling machines, boring...
Safety First
A growing apprehension of the possibilities of so safeguarding machines that the operator is reasonably sure that he incurs little risk of life or limb, would seem to render timely a few words on this...
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