scope:

This standard covers materials and performance requirements applicable to both metric and customary sizes of Types AB, B, BF, and BT and to customary sizes only of Types A and BP case hardened carbon steel tapping screws as used in the automotive and related industries. It is applicable also to sems employing the respective types of tapping screws. The standard does not apply to corrosion resistant (stainless) steel except for tapping screws fabricated from SAE 51410 which, when suitably processed, have been found to satisfy the performance requirements of this specification.

NOTE: Similar specifications pertaining to both metric and customary sizes of Type BSD and BSSD self-drilling tapping screws are covered in GM6172M.

CAUTION: Case hardened fasteners may be subject to delayed brittle fracture caused by hydrogen resulting from corrosion. Small amounts of water such as might condense from humid air can cause this type of failure, particularly in the presence of anodic surface coatings such as zinc or cadmium plate. Consequently, it is recommended that case hardened fasteners not be used in structural applications. 

The primary objective of this specification is to insure that screws form or cut mating threads in materials of construction into which they are normally driven, without deforming their own thread and without breaking during assembly or service.

Certain limitations on basic material and manufacturing processes have been incorporated because the size and configuration of the parts under consideration make them vulnerable to relatively small variations in chemistry, heat treatment, etc, and because experience has shown that in processing it is difficult to keep these variables consistently in balance. Until improved performance tests are developed these limitations will supplement the performance features of the specification.