NIMS Core Manual Turning Skills 262

alignment

The accurate positioning of parts in a mechanical system in relation to one another. Alignment on a lathe requires the workpiece and spindle to share a common centerline.

assembly

The process of joining objects. Assembly can include the use of fasteners, adhesives, or welding.

axes

An imaginary straight line that is used to measure the location of an object in three-dimensional space. The Cartesian axes on an engine lathe are the X axis, Z axis, and C axis.

axial runout

A type of alignment describing the workpiece when one end is concentric and the other is not. A part with axial runout is eccentric.

bar stock

Raw material purchased from metal manufacturers in the form of long bars. Bar stock may be round, square, or hexagonal.

bed

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

bill of materials

BOM. A report that lists the materials required to make a particular product and the cost of each individual component. A bill of materials includes all project materials, including any accessories and fasteners.

bonded abrasive wheel

A grinding tool made of grits that are held together with chemical bonding and formed into a circular shape. A bonded abrasive wheel rotates along the surface of a part to remove material.

boring

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

boring bar

A cylindrical toolholder used to position a single-point tool for internal cutting operations. A boring bar is used for internal taper turning operations on the lathe.

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.

cam locks

A type of fastener used to secure a chuck to a cam-lock spindle nose. A cam lock contains a base that a chuck key can attach to and turn the cam, which latches the cam-lock in place.

cam-lock spindle nose

A type of spindle nose in which the workholding device is held in place with cam-locks around its perimeter. Cam-lock spindle noses are often used on high-powered machines.

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. Cartesian coordinates are used to direct machine tool movements.

center

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

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 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-drilled

Using a center drill to make a tapered hole in the end of a part. Once a part is center-drilled, the center can support it using the tapered hole.

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 along a centerline.

chasing

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

chip evacuation

The proper removal 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

An unwanted piece of material that is removed from a workpiece. Chips are formed when a tool cuts or grinds a workpiece.

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 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.

coatings

A finish used for protective and decorative purposes. Coatings like paint or varnish are applied to products at the end of the part creation process.

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 makes smaller movements than the cross slide for making finer cuts.

compound rest feed dial

The lined scale on the compound rest handwheel that indicates the measurement of the feed. The compound rest feed dial sets the depth of cut.

compound rest handwheel

A hand-cranked wheel that moves the compound rest back and forth. The compound rest handwheel feeds the cutting tool for turning operations.

concave

Inwardly curved in shape. Concave surfaces can form during parting off operations if there is improper cutting tool alignment.

concentric

Having a common center or sharing the same axis with another object. When the workpiece and lathe spindle share a common centerline, they are concentric.

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 by positioning the tailstock off-center.

convex

Outwardly curved in shape. Convex surfaces can form during parting off operations if there is improper cutting tool alignment.

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 lever

A lever located on the carriage assembly that controls movement of the cross slide. The cross-slide feed lever can be set to automatically feed the carriage toward or away from the chuck.

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.

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 tool

A device made of hard, tough material that is used to remove metal by creating chips. Cutting tools used for lathe operations are usually single-point tools such as carbide inserts.

dead center

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

depth of cut

The distance that a cutting tool penetrates the surface of a workpiece. Depth of cut is set on the compound rest feed dial for taper turning operations on the lathe.

dial indicator

A measuring instrument used to indicate linear movement. Using a dial indicator is the best way to make sure a workpiece is properly aligned with the spindle.

diameter

The distance from one edge of the circle to the opposite end through the center. The diameter is always twice the size of the radius.

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.

dimensions

A measurement of space, especially length, width, and height. Dimensions of a part are detailed in a blueprint.

display panel

The screen that displays information about a machine for the operator. Display panels indicate the position of the workpiece on a manual milling machine.

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. DRO is capable of very precise measurements.

eccentric

Not having a common center. Eccentric rotating components do not share the same centerline, or axis.

engine lathe

The original and most basic type of manual lathe. An engine lathe holds a cylindrical workpiece on one or both ends.

facing

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

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.

fasteners

A device that holds objects together or locates them in relation to one another. Common fasteners include screws, bolts, and rivets.

feeds

The rate at which the cutting tool and the workpiece move in relation to one another. Feed is typically a linear movement.

feeler gage

A device of known thickness used to measure small distances. Feeler gages come in a range of sizes.

finishing

A cutting pass that emphasizes tight tolerances and smooth surface finish. Finishing is usually the last step in the machining process.

flex

The amount that a part bends due to pressure from the cutting tool. A smaller diameter part will flex less often if the tool is fed away from the chuck.

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.

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 dial

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.

grinder

A machine that uses an abrasive to remove material from the surface of a workpiece. Grinders include surface grinders, centerless grinders, and cylindrical grinders.

grinding

The use of an abrasive tool to remove material from a workpiece. Grinding operations commonly use abrasive grains bonded into a wheel shape.

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.

guide shoe

A sliding component on a taper attachment. The guide shoe slides on the guide bar and directs the cross slide feed at an angle to create a taper.

headstock

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

heat treatment

Controlled heating and cooling processes used to change a material's structure and alter its physical and mechanical properties. Heat treatment often adjusts a material's hardness.

height gage

A type of measuring instrument with a precision finished base, a perpendicular beam, and an indicator. A height gage can be used in conjunction with a planer gage to align a cutting tool to a lathe spindle.

hexagonal

Six-sided. Hexagonal workpieces can be held by self-centering and independent chucks.

ID

Internal diameter. The inner surface of a hole or cylindrical feature. ID operations on the lathe include drilling, reaming, and boring.

independent chuck

A type of chuck with jaws that can each move separately. Independent chucks can grip irregularly shaped workpieces during lathe operations.

internal diameter

ID. The inner surface of a hole or cylindrical feature. Internal diameter operations on the lathe include drilling, reaming, and boring.

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 machining operation that displaces material rather than cutting it. Knurling embeds a textured, rough pattern into a part's surface.

lathe

A machine tool used to create cylindrical parts. A lathe holds a cylindrical workpiece on one or both ends while a cutting tool is gradually passed along or into the surface of the rotating part.

lathe dog

A workholding device that clamps onto the workpiece and transmits rotary motion from the spindle of a lathe to the workpiece. The lathe dog allows a workpiece to be mounted between centers.

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.

live center

A type of center that uses bearings or friction so that the center rotates with the workpiece in the headstock. Live centers are also called driving-type centers.

machining

The process of removing material to form an object. Machining methods include milling, turning, and drilling.

manufacturer’s technical data references

Documents provided by a manufacturer that provide specific information about the products they manufacture. Machinists use manufacturer’s technical data references to help them select the proper cutting tool for a given operation.

metal cutting

A machining process that uses a tool to remove metal from a workpiece in the form of chips. Metal cutting operations include milling, drilling, and turning.

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 when in automatic mode.

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.

OD

Outside diameter. The outer surface of a cylindrical workpiece or feature. OD operations on the lathe include turning and parting off.

off-center

Any location on a part that deviates from the part's centerline. Off-center turning requires an independent chuck rather than a self-centering chuck.

offset turning

A turning operation on a lathe in which the workpiece centerline axis is not continuously aligned with the Z axis. Offset turning operations include taper turning.

operator

An employee who runs a machine. Operators are trained to safely set up, run, and maintain their particular machine.

origin

The fixed central point in the Cartesian coordinate system. The origin has a numerical value of zero at each axis.

outside diameter

OD. The outer surface of a cylindrical workpiece or feature. Outside diameter operations on the lathe include turning and parting off.

parallel

Two lines or axes that are equidistant at all points along their length. Parallel lines, axes, or components never touch or intersect.

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. Parting off, also known as cutting 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. The cross slide movement is perpendicular to the spindle axis.

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.

planer gage

A work aid consisting of two right-triangle metal blocks fastened together. A planer gage allows users to measure dimensions of parallel surfaces within a range by sliding one block onto another.

print

A document containing all the instructions necessary to manufacture a part. A print 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.

quick-change tooling

A set of toolholders that uses a master toolholder with a series of rapid, interchangeable toolholders. Quick-change tooling increases the speed of production, but operators must check alignment after changing tools.

radial alignment

A type of alignment describing whether or not the workpiece is concentric to the centerline of the lathe spindle. If a workpiece runs true, it has a proper radial alignment.

reaming

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

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.

roughing

A cutting pass that removes material without regard to surface finish. Roughing is often used to separate part pieces from a single sheet of material.

run true

Having a common center or sharing the same axis with another object. If a workpiece runs true, it shares a centerline with the lathe spindle.

runout

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

saddle

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

sanding

A form of grinding that uses a fine grain abrasive to remove small amounts of material. Sanding improves the finish of a surface.

self-centering chuck

A chuck with jaws that open and close together. Self-centering chucks accurately position a workpiece along the centerline of the chuck.

set screws

A type of screw with a rounded or cone-shaped end designed to fit into a matching recess. When loosened, set screws on the tailstock allow operators to offset the tailstock.

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.

short taper spindle nose

A type of spindle nose in which the workholding device is held in place with fasteners around its perimeter. Short taper spindle noses are often used on high-powered machines.

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.

speeds

The rate at which the workpiece passes the cutting tool at the point of contact. Surface speed has the greatest effect on tool life.

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 nose

A component of the spindle onto which the workholding device is mounted. The type of spindle nose on the lathe determines the appropriate workholding device to use.

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 finish

The degree of roughness and variation on the surface of a part after it has been manufactured. The surface finish of a part may need to be smooth or intentionally rough.

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 a center to support long workpieces or cutting tools, such as a drill bit.

tailstock offset

Repositioning the lathe tailstock a small distance off the spindle centerline. A tailstock offset is one method for turning long tapers between centers.

tangent

tan. The ratio of the side opposite an angle of a right triangle to the side adjacent to that angle. Finding the tangent of an angle helps in finding the measurement of the angle in degrees.

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 per foot

TPF. The change in diameter for each foot along the length of a tapered cylindrical part. Taper per foot is calculated by dividing the difference between large and small diameters by the length of the taper, then multiplying the result by 12.

taper per inch

TPI. The change in the diameter for each inch along the length of a tapered cylindrical part. Taper per inch is calculated by dividing the difference between large and small diameters by the length of the taper.

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.

thread gage

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

threaded spindle noses

A type of spindle nose that is screwed onto the spindle. Threaded spindle noses are often used on small lathes.

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 that may appear on the interior or exterior of an object. Threads help fasteners, such as screws, grip material and hold components together.

three-dimensional

A space that has length, width, and depth. Three-dimensional space can be represented by the Cartesian coordinate system.

tolerances

A blueprint specification indicating an unwanted but acceptable deviation from a given dimension. Tolerances state the allowable difference between a part 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 positioning 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.

turning

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

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.

workholding

A method or device for securing a workpiece for a machining operation. Workholding can include chucks, vises, and clamps.

workpiece

Any part that is being machined, formed, or otherwise worked on. Workpieces are turned on a 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.

Y axis

The Cartesian axis that represents up and down movement, perpendicular to the X axis. The Y axis is not utilized on a manual 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 and then resets the analog measuring devices or DRO display to zero.