Applicable to screw types as indicated by code symbols.
  • Type AB thread forming.
  • Type A thread forming, except for short lengths.
  • 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.

No. 8

Nominal Size or Basic Screw Dia. (Decimal)

0.1640 in
Applicable to Screw Types1 1
2
3
4

Max. Head Dia. (A)

0.322 in

Min. Head Dia. (A)

0.306 in

Max. Head Height (H)

0.115 in

Min. Head Height (H)

0.105 in

Min. Head Radius (R)

0.015 in

Ref. Recess Dia. (M)

0.176 in

Ref. Recess Depth (T)

0.095 in

Ref. Recess Width (N)

0.030 in

Driver Size

2

Max. Recess Penetration Gaging Depth

0.097 in

Min. Recess Penetration Gaging Depth

0.071 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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