Engine Lathe Operation 261

analog measurement

A type of readout that uses dials with scales inscribed on them to display dimensions on the lathe. Analog measurement is less precise than digital readout.

apron

A rectangular plate mounted to the saddle. The apron holds the carriage handwheel and cross-slide handwheel.

axial

Along or parallel to the workpiece axis. Axial depth of cut is controlled by the carriage-feed handwheel.

backlash

The relative movement of interlocked mechanical components due to slack, or extra space, between them. Backlash often occurs when motion is reversed.

bed

The base of the lathe. Beds provide a foundation for various machine tools.

boring

The process of enlarging an existing hole with a single-point tool. Boring is an inner diameter operation.

boring tool

A long bar used to position a single-point tool for boring operations. Boring tools may have adjustable or fixed diameters.

burrs

A rough, sharp edge remaining on a part after a cutting process. Burrs pose an injury risk and interfere with the fitting of parts.

C axis

The Cartesian axis describing motion around the Z axis. The C axis describes the rotation of the spindle on a lathe.

calipers

A measuring instrument with a pair of jaws on one end and a long beam containing a marked scale of unit divisions. Calipers can measure both internal and external features.

carriage assembly

The combination of components that make up the carriage. The carriage assembly includes the saddle, cross slide, compound rest, tool post, and cutting tool.

carriage handwheel

A hand-cranked wheel that moves the lathe carriage back and forth along the ways, parallel to the workpiece. The carriage handwheel positions the cutting tool for turning operations.

Cartesian coordinate system

A system that describes the location of an object by numerically expressing its distance from a fixed position along three linear axes, which are perpendicular to each other. Cartesian coordinates are used to direct machine tool movements.

center drilling

Cutting a wide center hole into the end of a workpiece using a special center drill bit. Center drilling can create a hole that can be used by a center to support the workpiece or can act as a pilot hole for drilling operations.

center drills

A type of drill with a wide shank and a 60° angle tip. The center drill is used to start a hole to ensure that the hole is machined in the right location.

center gage

An instrument that checks the angle of a cutting tool to a workpiece. Center gages help ensure the cutting tool is perpendicular to the workpiece for threading operations on a lathe.

center hole

A shallow hole used to locate other holemaking operations. Center holes are created with center drills.

centerline

An imaginary line that divides a shape into two equal halves or that runs through the center of a cylindrical object. A cylindrical workpiece rotates around a centerline, also called its axis.

centerline

An imaginary line that divides a shape into two equal halves or that runs through the center of a cylindrical object. The centerline of a cylindrical workpiece is the same as the spindle centerline and Z axis.

centers

A pointed cylindrical device that mounts in the headstock and tailstock to support a workpiece at one or both ends. Center are inserted into holes drilled into the ends of a workpiece.

chasing

A form of threading. Chasing occurs to repair damaged threads.

chatter

The development of surface imperfections on a workpiece caused by cutting tool vibration. Chatter occurs if the machine does not have sufficient rigidity or if the cutting tool is applied in an incorrect manner.

chip evacuation

The proper clearance of chips during a metal-cutting process. Chip evacuation can become an issue if the operation generates a lot of vibration, as with grooving, or when machining without enough cutting fluid, which can result in a damaged cutting tool or scrapped part.

chuck

A device that holds a workpiece in place as it rotates on a lathe or other machine. The chuck commonly has two, three, or four jaws that can be adjusted to fit various workpieces.

chuck key

A device used to tighten or loosen the bolts or cam-locks on a chuck. A chuck cannot be removed from a cam-lock spindle nose without the use of a chuck key.

collet

A slotted device that holds a workpiece or cutting tool in place as it rotates. A collet has a hole through which the workpiece or tool passes and is designed to hold specific dimensions.

compound rest

The part of the lathe that holds the tool post. The compound rest swivels to position the cutting tool and also makes smaller back-and-forth movements than the cross slide for making finer cuts.

concave

Inwardly curved in shape. Improper cutting tool alignment during parting off can result in the bottom surface of a part becoming concave.

conical taper

A cylindrical feature that gradually changes from a larger diameter to a smaller diameter at a constant ratio. Conical tapers are machined on the lathe using a taper attachment or the tailstock positioned off-center.

convex

Outwardly curved in shape. Improper cutting tool alignment during parting off can result in the bottom surface of a part becoming convex.

cross slide

The part of the carriage assembly on a lathe that holds the compound rest. The cross slide moves the cutting tool perpendicular to the workpiece.

cross-slide feed dial

The graduated scale on the cross slide that indicates the measurement of the feed. The cross-slide feed dial measures how far the cutting tool moves along the X axis.

cross-slide handwheel

A hand-cranked wheel that moves the cross slide on a lathe back and forth, perpendicular to the workpiece. The cross-slide handwheel brings the cutting tool into and out of contact with the workpiece during turning.

cutoff

A cutting operation performed on a lathe that uses a cutting tool to separate a finished part from the rest of the stock. Also known as parting off, cutoff is an outer diameter operation.

cutoff tool

A cutting tool designed to separate a finished workpiece from the bar stock. A cutoff tool is usually a thin blade of high-speed steel.

cutting fluid

A substance used to cool and lubricate a metal-cutting process. Cutting fluids are typically oil- or water-based liquids.

cutting inserts

A replaceable cutting tool with a geometric shape that has multiple cutting surfaces. Cutting inserts can be repositioned when a cutting edge has worn down since only one edge is used at a time.

cutting speed

The rate at which a workpiece and cutting tool move past one another at their point of contact. Cutting speed on a lathe measures the rate at which a workpiece rotates past a tool.

cutting variables

The changeable aspects of a given metal cutting operation. Cutting variables for lathe operations include speed, feed, and depth of cut.

deflecting

Unintentionally deviating from a straight line or plane when a force is applied. Deflecting in drilling can cause poor hole location and dimensions.

depth of cut

The amount of material removed by one pass of the cutting tool. Depth of cut measures how far the cutting tool penetrates the surface of the workpiece during a cut.

diameter

The distance between two opposing points on the edge of a circle passing through the center. The diameter divides the face of a cylindrical workpiece into two equal halves.

digital readout

DRO. A type of readout that uses an encoder attached to a machine that transfers information to a digital display. Digital readout is capable of very precise measurements.

drill chuck

A toolholder that tightens to grip holemaking tools. Drill chucks allow for the quick installation and removal of various tools, including drill bits, reamers, and taps.

drilling

The use of a multipoint tool to machine a new round hole into the surface of a workpiece. Drilling is an inner diameter operation.

drip method

A manual cutting fluid delivery method in which an operator uses a brush to apply fluid on the workpiece surface. The drip method is often used with oil-based cutting fluids.

DRO

Digital readout. A type of readout that uses an encoder attached to a machine that transfers information to a digital display. Digital readout is capable of very precise measurements.

encoders

A device that translates mechanical motion into a digital signal. Encoders send locations to a numerical display panel on a lathe.

engine lathe

The original and most basic type of manual lathe. An engine lathe uses a single-point cutting tool to remove material from a rotating cylindrical workpiece.

face

The flat, circular end of a cylindrical part. The face is perpendicular to the workpiece axis.

facing

An operation performed on a lathe that feeds a cutting tool across an end of a cylindrical workpiece to create a flat surface. Facing is an outer diameter operation.

feed

The rate at which a cutting tool travels along the length of a workpiece. Lathe feed describes a tool’s linear rate of travel along a workpiece surface.

feed

The rate at which the cutting tool advances along the workpiece per revolution or unit of time. Feed on the lathe is typically measured in inches or millimeters per revolution.

finishing

A final metal-cutting pass that emphasizes tight tolerances and a smooth surface finish. Finishing cuts often require faster speeds and a lighter depth of cut.

flexing

The amount that a part bends due to pressure from the cutting tool. Flexing is less drastic on smaller diameter parts if the tool is fed away from the chuck.

flutes

A straight or helical recessed feature on the periphery of a cutter or drill. Flutes allow chips to flow away from the cut.

form tool

A cutting tool ground to a specific shape that is used to create that shape in a workpiece surface. Form tools used for grooving on the lathe are often square or V-shaped.

form tools

A cutting tool ground to a specific shape that is used to create that shape in a workpiece surface. Form tools used for grooving on the lathe are often square or V-shaped.

graduated dials

An analog device that measures linear movement. Graduated dials are numbered collars attached to handwheels on the lathe that record and measure movement and positioning.

grooving

A machining operation performed on the lathe that cuts a narrow channel into the surface of a rotating cylindrical workpiece. Grooving can be an inner or outer diameter operation.

guide bar

An adjustable steel rod on a taper attachment. The guide bar sets the taper angle for taper turning.

headstock

The component of the lathe that holds the motor, gearbox, and spindle. The headstock powers the lathe.

ID

Inner diameter. Cutting operations that take place on the interior surface of a workpiece. Drilling, reaming, and boring are all inner diameter operations on a lathe.

inches per minute

ipm. The distance that the cutting tool advances in one minute. Inches per minute is a standard measurement for the feed of a cutting tool on the lathe.

inches per revolution

ipr. A measurement of how many inches a cutting tool advances along a workpiece in one revolution of that workpiece. Inches per revolution measures feed.

inner diameter

ID. Cutting operations that take place on the interior surface of a workpiece. Drilling, reaming, and boring are all inner diameter operations on a lathe.

known surface

A surface that can be used to take accurate measurements. A surface becomes known after it is machined to a definite measurement.

knurling

A forming process that adds a pattern on the exterior surface of a workpiece, slightly increasing the workpiece diameter by displacing material. Knurling produces a textured, rough pattern embedded into the part's surface, either for cosmetic reasons or better handling.

knurling

A forming process that adds a pattern on the exterior surface of a workpiece, slightly increasing the workpiece diameter by displacing material. Knurling produces a textured, rough pattern embedded into the part’s surface, either for cosmetic reasons or better handling.

layout dye

A fluid that is brushed on a metal workpiece before operation. Layout dye allows the lines and features to be seen more clearly.

meters per minute

m/min. The measurement of how many meters of workpiece material pass a cutting tool in one minute. Meters per minute measures cutting speed.

micrometer

A U-shaped measuring instrument with a threaded spindle that slowly advances toward a small anvil. A micrometer must be used to accurately measure the true diameter during and after a turning operation.

micrometer stop

A mechanical device attached to the ways of a lathe and mounted in front of or behind the carriage. The micrometer stop limits the travel of the carriage assembly and prevents it from hitting the chuck.

millimeters per minute

mm/min. The distance that the cutting tool advances in one minute. Millimeters per minute is a metric measurement for the feed of a cutting tool on the lathe.

millimeters per revolution

mm/rev. A measurement of how many millimeters a cutting tool advances along a workpiece in one revolution of that workpiece. Millimeters per revolution measures feed.

nib

A small protrusion or burr on a workpiece surface. Nibs form when a machinist aligns the cutting tool below the spindle centerline when setting up an engine lathe for operation.

numerical display panel

The screen that displays information about a machine for the operator. Numerical display panels indicate the position of the cutting tool on an engine lathe.

OD

Outer diameter. Cutting that takes place on the outer surface of a workpiece. Outer diameter operations on a lathe include turning, facing, and parting off.

outer diameter

OD. Cutting that takes place on the outer surface of a workpiece. Outer diameter operations include turning, facing, and parting off.

parallel faces

Two surfaces of a workpiece with all opposing points equidistant from each other. Parallel surfaces are often a requirement on cylindrical workpieces machined on an engine lathe.

parting off

A cutting operation performed on a lathe that uses a cutting tool to separate a finished part from the rest of the stock. Also known as cutting off, parting off is an outer diameter operation.

periphery

The outer edge or rim of an object or tool. Both the periphery and face of the cutting tool are used in milling.

perpendicular

Meeting at a 90° angle. Cross-slide movement is perpendicular to the spindle axis.

personal protective equipment

PPE. Any of the various articles of clothing or safeguarding devices that operators are required to wear to ensure their safety. Personal protective equipment includes safety glasses and ear plugs.

pin gage

A type of gage available in a set and used like a plug gage. Pin gages are available in 0.001 in. increments, ranging from 0.028 to 1.000 inch, and are useful when measuring maximum and minimum hole sizes.

pitch

The distance between a point on an individual thread to the corresponding point on the next thread. Pitches range from coarse, with few threads, to fine, with many threads.

pitch diameter

The measured distance between points in the grooves between threads. Pitch diameter is the theoretical point where the threads of a fastener and the threads of a hole meet.

power feed

A method of advancing a workpiece into a machine automatically. Power feed is controlled by an on-off lever on the apron of the saddle on the lathe.

print

A document containing all the instructions necessary to manufacture a part. A print, also known as a blueprint, includes a part drawing, dimensions, and notes.

quick-change gearbox

A lathe component that houses the gears that control the power transferred from the motor to the spindle. The quick-change gearbox allows the spindle speed and rotation to be adjusted quickly.

radial

Perpendicular to the workpiece axis. Radial depth of cut is controlled by the cross-slide feed dial.

readout

The process of reading information from a machine and displaying it in an understandable form. Readout measures locations and movements on a lathe and can be analog or digital.

reamer

A multipoint, or multi-edge, cutting tool with straight cutting edges, used to enlarge or smooth holes that have been previously drilled. Reamers may have straight or helical flutes.

reaming

The process of enlarging or smoothing an existing hole with a multipoint tool. Reaming is an inner diameter operation.

revolutions per minute

rpm. A unit of measurement that indicates the number of revolutions a machine component makes in one minute. Revolutions per minute measures rotation from the center of a tool or spindle.

rough cuts

The quick removal of metal from a workpiece without regard to tolerances or finish. Rough cuts are made with high feed rates and large depths of cut.

rpm

Revolutions per minute. A unit of measurement that indicates the number of revolutions a machine component makes in one minute. Revolutions per minute measures rotation from the center of a tool or spindle.

saddle

The base of the lathe carriage assembly. The saddle rides along the ways to reposition the carriage assembly.

set zero

To establish a starting point on a workpiece or machine by setting the coordinate values to zero. To set zero, or zero the tool, an operator positions the tool in a location and then resets the analog measuring devices or DRO display to zero.

setup

All the necessary preparation that occurs on a machine before an operation can be executed. Setup includes preparing machines, tools, and materials.

shank

A cylindrical part of a tool or device, such as a drill or a reamer. The shank of a center drill is short and wide.

single-point tool

A cutting tool that has one single cutting edge. Single-point cutting tools are usually made of high-speed steel or carbide.

specifications

The design parameters that set the limits of acceptable deviation for a part’s intended application. Specifications are also called specs.

spindle

A component of a lathe’s headstock that rotates the workpiece. The spindle can be mounted with a workholding device to support the workpiece.

spindle speed

The rate at which the machine spindle rotates. Spindle speed for the lathe is measured in revolutions per minute (rpm).

spindle speed

The rate at which the machine spindle rotates. Spindle speed for the lathe is measured in revolutions per minute.

spindle speed selector

A device that controls spindle speed. The spindle speed selector is a dial located on the gearbox or headstock of an engine lathe that allows an operator to select and adjust the spindle’s revolutions per minute.

steady rest

A device used to support long rotating workpieces. Steady rests can support longer workpieces for high-pressure operations on the lathe, such as knurling.

surface feet per minute

sfm. The measurement of how many feet of workpiece material pass a cutting tool in one minute. Surface feet per minute measures cutting speed.

surface grinding

A common grinding process that uses a rotating grinding wheel to wear away precise amounts of a flat workpiece surface. Surface grinding is often one part of a sequence of machining operations.

tailstock

A toolholder and mount opposite from the headstock. The tailstock can hold holemaking tools or a center and moves parallel to the workpiece.

tailstock feed dial

The graduated scale on the tailstock feedwheel that indicates the measurement of the feed. The tailstock feed dial measures how far the cutting tool moves along the Z axis.

tap

A cylindrical shaped, threaded device that either cuts or presses threads into the interior of a drilled hole. A tap’s external teeth match the internal threads it is designed to produce.

taper attachment

A specialized lathe attachment that includes an angled guide bar and shoe used to machine a taper on a cylindrical part. A taper attachment is clamped to the lathe saddle and connects to the cross slide to guide its movement during taper turning.

taper ring gage

A measuring device with an internal taper. Taper ring gages are used to determine taper angle of a cylindrical part in taper turning operations.

taper turning

A lathe cutting operation that gradually increases or decreases the diameter along a length of the workpiece to create a conical shape. Taper turning is an outer diameter operation.

taper turning

A lathe cutting operation that gradually increases or decreases the diameter along the workpiece length to create a conical shape. Taper turning is an outer diameter operation.

tapping

The process of cutting internal threads in a round hole with a multipoint tool. Tapping is performed only after first drilling a hole.

telescope gage

A measuring instrument with a spring-loaded device used to check the inner diameter of a part. Telescope gages are then measured with a micrometer to get the proper value.

thread gage

A measuring instrument used to inspect the threads of a part. Thread gages are made for either internal or external thread inspection.

threading

The process of cutting a long, helical groove into the exterior of a cylindrical workpiece with a single-point tool. Threading can also be an inner diameter operation, though outer diameter threading is more common.

threads

A long, spiral ridge around the exterior or interior of a cylindrically shaped object. Threads are used to fasten or provide motion.

tolerances

The acceptable variation from a specified dimension. Tolerances indicate allowable difference between a physical feature and its intended design.

tool post

A lathe component that sits on the compound rest of the carriage assembly. The tool post contains a slot for mounting the toolholder and cutting tool.

touch off

To determine the exact location of a tool tip by touching it against an object with a known measurement. To touch off establishes a starting point for the cutting tool on the workpiece.

turning

A machining operation that rotates a cylindrical workpiece while a single-point tool is guided along the length of a part. Turning is performed on a lathe.

Unified threads

A thread set to a measurement standard based on inches. Unified threads conform to specifications of the American Society of Mechanical Engineers (ASME) and the American National Standards Institute (ANSI), both of which set standards in the United States.

walking

Unintentionally moving off-center or away from the intended tool location. Walking is another term describing deflection.

ways

A set of parallel tracks along which a machine component moves. The ways allow the carriage and tailstock to move along the bed of the lathe.

X axis

The Cartesian axis describing cutting tool motion toward and away from the spindle centerline. The X axis is perpendicular to the spindle centerline on a lathe.

Z axis

The Cartesian axis describing the location of the spindle centerline. The Z axis is always parallel to the spindle on a lathe.

zero the tool

To establish a starting point on a workpiece or machine by setting the coordinate values to zero. To zero the tool, or set zero, an operator positions the tool in a location then resets the analog measuring devices or DRO display to zero.