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.

This type of recess has a large center opening, tapered wings, and blunt bottom, with all edges relieved or rounded.
Unit of Measure

Manufacturer

Manufacturer

Industrial Fasteners Institute

Specifications

Product

Tapping Screws

Unit of Measure

English

Type

Type I

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

Ref. Recess Dia. (M)

0.384 in

Ref. Recess Depth (T)

0.226 in

Ref. Recess Width (N)

0.065 in

Driver Size

4

Max. Recess Penetration Gaging Depth

0.218 in

Min. Recess Penetration Gaging Depth

0.194 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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