Engine Lathe Operation 261

alignment

The accurate positioning of machine components. Alignment on a lathe requires the workpiece and spindle to share a common centerline.

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.

angle adjustable tool rest

A surface that supports a workpiece at a particular angle against the grinding wheel. An angle adjustable tool rest offers precise grinding for high-speed steel tools.

apron

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

backlash

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

bench grinder

A type of stationary grinding machine with an abrasive wheel that is fixed to a worktable. A bench grinder can be used to reshape or resharpen high-speed steel tools.

boring

A lathe cutting operation in which an existing hole is enlarged with a single-point tool. Boring is an internal diameter operation that removes a small amount of material to improve the surface finish and roundness of a hole.

boring tool

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

built-up edge

The gathering of material against the face of the tool tip that impacts surface finish. A built-up edge can happen from machining softer metals.

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.

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.

carbide

A common cutting tool material created by combining carbon with a hard metal, such as titanium or tungsten. Carbide cutting tools are the most commonly used in the metal cutting industry.

carriage

A component of the lathe that slides along the ways parallel to the spindle axis. The carriage houses the cross slide.

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 cutting operations.

center drill

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 drilling

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

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. The centerline of a cylindrical workpiece is the same as the spindle centerline and Z axis.

chase

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 breaker

A contour behind the cutting part of a cutting tool that helps prevent chips from clogging. A chip breaker improves chip evacuation.

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.

chips

A piece of material that is removed from a workpiece during cutting, grinding, or other manufacturing operations. Chips are tiny curls, shards, fragments, or particles of material that can damage the face, eyes, or skin if ejected toward the operator.

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.

clearance

The amount of space between the cutting edge and the flank of the tool. Clearance between the flank and cutting edge prevents the workpiece from rubbing against the flank, which can lead to rapid tool wear.

compressed air

Air that has been forced into a small space at high pressure. Compressed air is dangerous to use to clean chips during machining.

concentricity

A geometric tolerance that creates a tolerance zone for the median points of a cylindrical feature. Concentricity is related to tolerance.

conical taper

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

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 perpendicular to the workpiece. The cross slide handwheel moves the cutting tool toward or away from the workpiece.

cutoff

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

cutoff tool

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

cutting fluid

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

cutting speeds

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.

dead center

A center that remains stationary during a turning operation. A dead center does not turn with the workpiece.

deflecting

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

Depth of cut

DOC. 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.

dial indicator

A measuring instrument used to indicate linear movement, roundness, and runout. Using a dial indicator is the best way to determine runout in order to ensure the workpiece is properly aligned with the spindle.

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.

DOC

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

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 multi-point tool to machine a new round hole into the surface of a workpiece. Drilling is an internal diameter operation.

drip method

A manual coolant-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. DRO is capable of very precise measurements.

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.

facing

A lathe cutting operation 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 ratio

An expression that compares the measurements on a lathe's feed dial with the amount of material the tool removes. Feed ratios for feed dials with diameter measurements are 1:1, which means the tool removes the same amount of material listed on the dial, while a 2:1 ratio means that the dial uses radius measurements, and the tool removes twice the diametric amount on the dial.

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.

float

Removing any locks or binding to allow self-alignment of machine components. Float the tailstock during tapping.

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.

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.

grinding

A machining process in which an abrasive is used to precisely cut and shape the surface of a workpiece. Grinding operations commonly use abrasive grains bonded into the shape of a wheel.

grinding wheel

A disc made of a bonded abrasive used to remove material from a workpiece surface. A grinding wheel rotates and shears away microscopic chips of material and is used to grind lathe tool bits.

grooving

A lathe cutting operation that cuts a narrow channel into 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.

half-nut lever

A lever that is engaged when the line on the threading dial matches up with the proper reference mark. The half-nut lever is attached to the side of the apron of the lathe and is only used in threading operations.

headstock

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

helical

Having a spiral shape. Threads have helical grooves.

high-speed steel

HSS. A common cutting tool material that is relatively inexpensive and offers excellent toughness. High-speed steel tools can be ground to be repurposed and reused.

HSS

High-speed steel. A common cutting tool material that is relatively inexpensive and offers excellent toughness. HSS tools can be grinded to be repurposed and reused.

inch

in. A small unit of linear measurement in the English system. One inch equals approximately 2.54 centimeters in the metric system.

Inner diameter

ID operations. Cutting operations that take place on the interior surface of a workpiece. Internal diameter operations on the lathe include drilling, reaming, and boring.

inserts

A removable, replaceable cutting tool with multiple edges that can be rotated into place. Indexable cutting inserts must be replaced or repositioned when a cutting edge wears out.

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.

Leadscrew

A long threaded bar that transfers power between lathe components. The leadscrew is located beneath the lathe bed and extends from the headstock to the end of the lathe.

left-hand threads

A type of thread that is turned in a counterclockwise direction. Left-hand threads are rare.

lever

A simple machine consisting of a rigid bar that pivots around a fixed point. Lever-style indicators are sensitive to angles.

lubrication

A substance that reduces friction between two surfaces in relative motion. Cutting fluids provide lubrication for engine lathe operations.

mating nut

A threaded device that clamps around the leadscrew when engaged. The mating nut can have a gap between the leadscrew that causes backlash.

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

mm. A small unit of linear measurement in the metric system. One millimeter is equal to 0.1 of a centimeter metric and 0.039 of an inch U.S. customary.

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.

Outer diameter

OD operations. Cutting that takes place on the outer surface of a cylindrical or round workpiece. Outside diameter operations on the lathe include turning, facing, and parting off.

parallel faces

Two surfaces of a workpiece with all opposing points equidistant from each other. Parallel faces 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. Parting off, also known as cutoff, is an outer diameter operation.

parting tool

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

pecking

A drilling operation that periodically retracts the tool to clear chips or flood the hole with coolant. Peck drilling is often used for holes that are deeper than the drill diameter.

periphery

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

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.

plunger

A component of a measuring instrument that is pressed against a part to record a reading. When pressed, the plunger is pushed inside the base of the measuring instrument.

precision-ground stone

A tool made of steel or another hard material that is used to remove burrs or flatten machine parts. A precision-ground flat stone ensures that the mill table is flat.

protractor

A tool used to measure angles. A basic protractor is a semi-circular device with angle measurement markings.

quick change gearbox

The location of the gears that control the power being transferred from the lathe motor to the spindle. The quick change gearbox allows the spindle speed and rotation to be adjusted quickly.

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

A lathe cutting operation that enlarges an existing hole with a multi-point tool by removing small amounts of material from the interior surface of a hole. Reaming is an internal diameter operation that achieves tight tolerances and refined surface finishes.

respirator

A breathing device worn to prevent inhalation of hazardous substances. A respirator should be worn during grinding to prevent injury.

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.

right-hand threads

A type of thread that is turned in a clockwise direction. Most fasteners have right-hand threads.

roughing

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. Rpm measures rotation from the center of a tool or spindle.

runout

When two rotating objects do not share the same axis of rotation on the centerline. Runout determines the accumulated position error and deviation of a workpiece exterior or interior from a center axis as the workpiece rotates.

safety glasses

A form of protective eyewear, usually made of thick plastic, that shields the eyes from flying debris and other potentially hazardous materials. Safety glasses protect machine operators from chips.

sight glasses

A device with a visible window located on a machine that shows the level of liquid in a reserve. Sight glasses are located in multiple places on an engine lathe.

single-point tool

A cutting tool that has a single cutting edge. Single-point cutting tools are primarily used for operations on a lathe.

spindle speed

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

steady rest

A device used to support long rotating workpieces. A steady rest 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 component of an engine lathe opposite the headstock that supports the end of longer workpieces. The tailstock can be fitted with a cutting tool.

tailstock feed dial

The graduated scale on the tailstock feed wheel 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

A cylindrical feature that gradually changes from a larger diameter to a smaller diameter at a constant ratio. A taper can be machined on the lathe using a taper attachment or unintentionally during facing.

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. A taper ring gage is 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.

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 dial

A rotating dial with lines and numbers that is used to precisely set the leadscrew and carriage positions in relationship to the workpiece. The thread dial allows the lathe to repeatedly return to the same position.

thread micrometer

A U-shaped measuring instrument with a V-shaped anvil and a cone-shaped spindle. A thread micrometer is used to measure a thread's pitch diameter.

thread plug gage

A hardened, cylindrical go/no-go gage used to inspect the fit of threads in a hole. Thread plug gages are available in standardized sizes.

thread ring gage

A disk of heavy metal with a central, threaded hole made to match a particular OD thread. The gage is screwed onto the part being inspected as though the two are mating parts.

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 spiraling groove machined in the interior or exterior of a part. Threads allow compatible fasteners to connect to and move about each other.

threads per inch

TPI. The number of threads along the tap within one inch. Threads per inch are used to determine pitch and achieve unified threads.

tolerances

A specification indicating an unwanted but acceptable deviation from a given dimension. Tolerances can determine if parts must be discarded or reworked.

tool post

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

toolpath

The course followed by the tool as it creates the workpiece. Toolpaths are described by a series of coordinate positions.

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 lathe cutting operation that rotates a cylindrical workpiece while gradually passing the cutting tool along the surface of the rotating part. Turning is the most common cutting operation 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 deviating from a straight line or plane when a force is applied. Walking, also known as deflecting, in drilling can cause poor hole location and dimensions.

ways

A set of parallel tracks that allow machine tool components to move accurately. The ways on an engine lathe allow the carriage and tailstock to move along the bed.