Glossary

Milling cutter for machining T-slots. Desired T-slot shape is reverse of cutter shape.

Accessory that mounts in a turning machine’s tailstock for center-drilling chucked work and tapping. See chuck.

Extended flat portion of tapered drill shank, endmill or other tool that allows maximum power transmission and proper positioning of the tool. Reverse shape of the machine-spindle slot into which it fits.

Cylindrical tool that cuts internal threads and has flutes to remove chips and carry tapping fluid to the point of cut. Normally used on a drill press or tapping machine but also may be operated manually. See tapping.

Reamer designed to produce a reamed hole with a specified taper. Principles of standard reamers apply. See reamer.

Guide to which a cross slide is attached that permits the turning of tapers without disturbing the alignment of the tailstock. Also permits taper boring.

Machining operation in which a tap, with teeth on its periphery, cuts internal threads in a predrilled hole having a smaller diameter than the tap diameter. Threads are formed by a combined rotary and axial-relative motion between tap and workpiece. See tap.

Fits in a drill-press spindle and automatically reverses the tap when the thread is completed, ensuring proper retraction of the tool.

Production machine used for high-volume tapping. Offers repeatability, high production rates and reduced tap breakage. Comes in a variety of configurations, including indexing units with multiple tapping spindles. Precise stroke-depth settings and automatic features generally make tapping machines cost-effective.

Device used to “walk” a teachable robot through a new task.

1. In heat-treatment, reheating hardened steel or hardened cast iron to a given temperature below the eutectoid temperature to decrease hardness and increase toughness. The process also is sometimes applied to normalized steel. 2. In nonferrous alloys and in some ferrous alloys (steels that cannot be hardened by heat-treatment), the hardness and strength produced by mechanical or thermal treatment, or both, and characterized by a certain structure, mechanical properties or reduction in area during cold working.

In tensile testing, the ratio of maximum load to original cross-sectional area. Also called ultimate strength. Compare with yield strength.

Die-type external threading tool. Makes final threading pass.

Typically a form grinder as well as a thread grinder, this machine differs from other grinders in that precision gears and leadscrews ensure a precise traverse to impart the correct lead to a thread.

Chipless, cold-forming material-displacement process where a rolling head is pressed into the workpiece to create threads. The material is stressed beyond its yield point, which causes it to be deformed platically and permanently. There are three basic types of rolling heads: axial, radial and tangential.

Process of both external (e.g., thread milling) and internal (e.g., tapping, thread milling) cutting, turning and rolling of threads into particular material. Standardized specifications are available to determine the desired results of the threading process. Numerous thread-series designations are written for specific applications. Threading often is performed on a lathe. Specifications such as thread height are critical in determining the strength of the threads. The material used is taken into consideration in determining the expected results of any particular application for that threaded piece. In external threading, a calculated depth is required as well as a particular angle to the cut. To perform internal threading, the exact diameter to bore the hole is critical before threading. The threads are distinguished from one another by the amount of tolerance and/or allowance that is specified. See turning.

Typically takes the form of multispindle, universal threading machines that use dieheads and thread chasers to cut threads, often automatically or semiautomatically. Threading also is performed on lathes and automatic screw machines.

Hole or cavity cut in a solid shape that connects with other holes or extends all the way through the workpiece.

Often used as a tool coating. AlTiN indicates the aluminum content is greater than the titanium. See coated tools.

Extremely hard material added to tungsten carbide to reduce cratering and built-up edge. Also used as a tool coating. See coated tools.

Often used as a tool coating. See coated tools.

Added to titanium-carbide tooling to permit machining of hard metals at high speeds. Also used as a tool coating. See coated tools.

Minimum and maximum amount a workpiece dimension is allowed to vary from a set standard and still be acceptable.

Group of alloy steels which, after proper heat treatment, provide the combination of properties required for cutting tool and die applications. The American Iron and Steel Institute divides tool steels into six major categories: water hardening, shock resisting, cold work, hot work, special purpose and high speed.

Carriage or drum attached to a machining center that holds tools until needed; when a tool is needed, the toolchanger inserts the tool into the machine spindle. See automatic toolchanger.

Secures a cutting tool during a machining operation. Basic types include block, cartridge, chuck, collet, fixed, modular, quick-change and rotating.

2-D or 3-D path generated by program code or a CAM system and followed by tool when machining a part.

High-precision lathe built to hold tighter tolerances than regular, general-purpose lathes can hold. See lathe; turning machine.

Finger of metal that contacts a cutter edge during resharpening on a tool and cutter grinder, ensuring accurate location of edges so they are properly ground.

Combined variations of all dimensions of a workpiece, measured with an indicator, determined by rotating the part 360°.

Tool’s ability to resist breaking during cutting.

Used to duplicate a workpiece. A stylus connected to a servo traces a template or sample workpiece. The attachment directs the movements of a machine tool that cuts a duplicate workpiece. For machining complex parts.

Oil that is present in a metalworking fluid mix that is not from the product concentrate. The usual sources are machine tool lubrication system leaks.

Temperature range in which austenite forms as a tool is heated and disappears as the tool cools. This range is critical and must be known in order to heat-treat tooling.

Drilling deep holes that are too large to be drilled by high-pressure coolant drills or gundrills. Trepanning generates a solid core and normally requires a big, powerful machine. Shallow trepanning operations can be performed on modified engine or turret lathes or on boring machines. See boring; drilling; spade drilling.

Using a diamond or other dressing tool to ensure that a grinding wheel is round and concentric and will not vibrate at required speeds. Weights also are used to balance the wheel. Also performed to impart a contour to the wheel’s face. See dressing.

Intermetallic compound consisting of equal parts, by atomic weight, of tungsten and carbon. Sometimes tungsten carbide is used in reference to the cemented tungsten carbide material with cobalt added and/or with titanium carbide or tantalum carbide added. Thus, the tungsten carbide may be used to refer to pure tungsten carbide as well as co-bonded tungsten carbide, which may or may not contain added titanium carbide and/or tantalum carbide.

Workpiece is held in a chuck, mounted on a face plate or secured between centers and rotated while a cutting tool, normally a single-point tool, is fed into it along its periphery or across its end or face. Takes the form of straight turning (cutting along the periphery of the workpiece); taper turning (creating a taper); step turning (turning different-size diameters on the same work); chamfering (beveling an edge or shoulder); facing (cutting on an end); turning threads (usually external but can be internal); roughing (high-volume metal removal); and finishing (final light cuts). Performed on lathes, turning centers, chucking machines, automatic screw machines and similar machines.

Any machine that rotates a workpiece while feeding a cutting tool into it. See lathe.

Differs from engine lathe in that the normal compound rest is replaced by pivoting, multitool turrets mounted on the cross slide and tailstock. See lathe.

Variation of the vertical milling machine; has a movable ram mounted on a swivel base atop the column, providing positioning flexibility. See mill, milling machine.

Most common type of drill, having two or more cutting edges, and having helical grooves adjacent thereto for the passage of chips and for admitting coolant to the cutting edges. Twist drills are used either for originating holes or for enlarging existing holes. Standard twist drills come in fractional sizes from 1¼16" to 11¼2", wire-gage sizes from 1 to 80, letter sizes A to Z and metric sizes.