Applicable to screw types as indicated by code symbols.
  • Type AB thread forming.
  • Types B and BP thread forming and Types BF and BT thread cutting.
  • Type C thread forming and Types D, F, G, and T thread cutting.
Unit of Measure

Manufacturer

Manufacturer

Industrial Fasteners Institute

Specifications

Product

Tapping Screws

Unit of Measure

English

Nominal Size or Basic Screw Dia.

5/16 in

Nominal Size or Basic Screw Dia. (Decimal)

0.3125 in
Applicable to Screw Types1 1
3
4

Max. Width Across Flats (A)

0.500 in

Min. Width Across Flats (A)

0.489 in

Min. Width Across Corners (W)

0.545 in

Max. Head Height (H)

0.230 in

Min. Head Height (H)

0.208 in

Max. Washer Dia. (B)

0.676 in

Min. Washer Dia. (B)

0.624 in

Max. Washer Thickness (U)

0.055 in

Min. Washer Thickness (U)

0.035 in

Min. Protrusion Beyond Gaging Ring (F)

0.125 in

Codes and Standards

Codes and Standards

Abstract of ASME B18.6.4 1998
  • 1 1 = Circle, 2 = Diamond, 3 = Triangle, 4 = Square
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