Taper Turning on the Engine Lathe 311

American Standard

A standard variety of steep taper. American Standard tapers are used extensively in CNC mills.

angle with the centerline

½α. Half the included angle, measured in degrees from the centerline axis of a cylindrical part. Calculating the angle of the centerline is required to taper turn using the compound rest.

anvil

A fixed jaw against which an object to be measured is placed. The anvil on a micrometer comes in various designs, such as flat or rounded, and provides the surface from which measurements are taken.

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.

Brown & Sharpe

A standard variety of long taper. The Brown & Sharpe tapers are mostly used in milling and grinding machines but are also sometimes found in lathes.

centers

A cylindrical workholding device with a pointed tip. Centers are inserted into holes drilled into one or both ends of a workpiece.

clearance

An amount of space between two objects or components that is necessary to avoid contact. Clearance allows an operator to feed a boring bar into a drilled hole without damaging the tool or workpiece when turning an internal taper using a taper attachment or the compound rest.

compound rest

The part of the lathe that allows for angular adjustment of the cutting tool. The compound rest sits on the carriage and supports the tool post.

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.

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.

face

The flat, circular end of a cylindrical workpiece opposite the spindle. A part face is often the smaller diameter of an external taper.

gage blocks

A hardened steel block that is manufactured with highly accurate dimensions. Gage blocks are available in a set of standardized sizes.

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.

included angle

α. The angle between two defined features. The included angle on a taper is created by the change from one diameter to another diameter of different size.

Jarno

A standard variety of long taper. The Jarno taper mostly occurs in drilling and grinding machines.

layout dye

A colored fluid that a machinist brushes or sprays on a workpiece during layout. Layout dye allows surface marks 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.

long taper

A taper that is typically long in length with a relatively shallow angle. Long tapers on machine components allow the components to be self-holding.

micrometer

A U-shaped measuring instrument with a threaded spindle that slowly advances toward a small anvil. Micrometers are available in numerous types for measuring assorted dimensions and features.

Morse taper

A standard variety of long taper. Also known as a locking taper, a Morse taper is used in a wide variety of machines, especially lathes and exclusively in twist drill shanks.

ratio

A numerical expression representing proportion that uses two numbers separated by a colon. Tapers can be expressed in a ratio or as taper per foot or taper per inch.

self-holding

A taper designed to be held in a spindle by friction. A self-holding taper has a long taper typically with a 2° or 3° angle.

self-releasing

A taper designed to be released and reloaded easily. A self-releasing taper has a steep taper angle.

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.

sine bar

A workholding and measuring device that is composed of a steel bar with matching cylinders at each end. Sine bars allow workpieces to be set up at various angles for machining and measuring part surfaces, such as tapers.

steep taper

A taper that is typically short in length with a relatively dramatic angle. Steep tapers on machine components allow the components to be self-releasing.

surface plate

A hard, flat surface, usually made of granite, that is used as a base for inspecting parts. Surface plates provide the flat surface for sine bars to rest on.

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

For a cylindrical part, a gradual decrease in diameter from one end to another. A taper in a flat or rectangular part is an angled surface that gradually changes from a larger height to a smaller height at a constant slope or incline.

taper attachment

A specialized lathe attachment that includes an angled guide bar and shoe. A taper attachment connects to the cross slide to guide its movement during taper turning.

taper micrometer

A U-shaped measuring instrument with a threaded spindle that slowly advances toward a small sine bar mounted on an anvil. Taper micrometers can measure taper angles without removing the workpiece from the chuck.

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 ring gage

A hardened, round gage with an internal taper used specifically to determine the taper angle of a cylindrical part. A taper ring gage can be used without removing the workpiece from the chuck.

TPF

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

TPI

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

X axis

An axis in the Cartesian coordinate system that is perpendicular to the Z and Y axes. On the lathe, the X axis is perpendicular to the axis of the spindle and workpiece.