Glossary Terms

Unintentional surface irregularities that occur at infrequent or varying intervals, such as cracks, blowholes, checks, ridges and scratches. The effect of flows is not included in roughness average measurement. See lay; roughness; waviness.

Hand-operated hose and nozzle added to machine’s cutting-fluid-application system to permit manual flushing of table and workpiece areas.

Grooves and spaces in the body of a tool that permit chip removal from, and cutting-fluid application to, the point of cut.

Cutting straight or spiral grooves in drills, endmills, reamers and taps to improve cutting action and remove chips.

Rotary cutting tool employing one or more single-point tools for plane surfacing.

Workpiece rest or supporting device attached to the carriage that “follows” the cutting tool, keeping support near the point of cut. See steady rest.

Cutter shaped to cut stepped, angular or irregular forms in the workpiece. The cutting-edge contour corresponds to the workpiece shape required. The cutter can often be reground repeatedly without changing the cutting-edge shape. Two general classes: straight and circular.

Used to roll splines, gears, worms and threads. Cold-forming machine for production processing of previously machined parts. See broaching machine.

1. Maximum principal true stress at fracture. Usually refers to unnotched tensile specimens. 2. True stress (hypothetically) that will cause fracture without further deformation at any given strain.

Critical value (KIC) of stress intensity. A material property.

Group of carbon steels designated by the American Iron and Steel Institute numerical classification are free machining grades: AISI 1108, 1109, 1110, etc., up to AISI 1151 for a total of 14 grades. AISI 1211, 1212, 1213, 1215 and 12L14 carbon steels are also free machining grades.

Characteristic of abrasive grains that describes their tendency to fracture or break apart when hit or placed under pressure. Highly friable abrasives cut more easily, but wear faster than other abrasives. Friable abrasives are usually used on soft, gummy materials or where heat produced by worn grits must be carefully controlled.