| 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. |