Technology Education Department
Technical Drawing Program

R - radius - distance from center to edge of circle or arc

Ø - diameter - distance from edge to edge of circle through the center

TYP - typical - when same values or sizes are used in other locations on a drawing

REF - reference - used to indicate a general measurement for checking overall size, noncritical measurements

- centerline - to indicate the center locatioon of symetrical shapes

- depth - to indicate how deep a hole is drilled

- counter-bore - used to create over-sized hole to recess the head of a screw or bolt

- counter-sink - used to taper the top portion of a hole to accept a flathead screw

- spot-face - used to create a smooth surface at the top of a hole, usually very shallow in depth

FAO - finished all over - all surfaces have been machined, sanded, buffed or polished

CI - cast iron - material used to make parts cast in molds in a foundry

CRS - cold rolled steel - type of steel sheet made by passing steel through rollers

AL - aluminum - soft, light weight, easily worked metal

UNC - Unified National Course - classification of screw threads

UNF - Unified National Fine - classification of screw threads

UNEF - Unified National Extra Fine - classification of screw threads

ANSI - American National Standards Institute - governmental organization that establishes uniform standards, procedures and practices for the design, engineering and drafting of consumer products

ISO - International Standards Organization - international organization that establishes uniform standards, procedures and practices for the design, engineering and drafting of international consumer products

Mil Std. - U. S. Military - governmental body that establishes uniform standards, procedures and practices for the design, engineering and drafting of products purchased by the government

SAE - Society of Automotive Engineers - non-profit professional organization that establishes uniform standards, procedures and practices for the design, engineering and drafting of automotive products

ASTM - American Society for Testing Materials - non-profit professional organization that establishes uniform standards, procedures and practices for the design, engineering and testing of materials used in products

UL - Underwriters Laboratory - private organization that tests products for safety and reliability against establishes standards

SI - Systems International - metric system of measurements

BOCA - Building Officials Congress of America - governmental organization that establishes minimum construction procedures and practices for design, engineering and building of structures

CAD - Computer Aided Design - software used by engineers and architects to create three dimensional models of products and structures on a computer

CADD - Computer Assisted Drafting & Design - software used by engineers and architects to create two and three dimensional drawings of products and structures on a computer