ASME B18.6.3 pdf download

ASME B18.6.3 pdf download.Machine Screws and Machine Screw Nuts.
Penetration gaging is a test to determine the suitability of recesses in the heads of screws and may be used to indicate deficiencies in the dimensional aspects of the recesses specified in the dimensional tables. (Refer to Figs. 111-1, 111-2,111-3, and 111-4 for illustrations of penetration gages for Types 1. IA, II, and Ill recesses, respectively.) Penetrations that are too deep indicate the possibility of a thin section between head and shank of screw, a weakness that might result in twisting-off screw heads during tightening of the screws. Screws with shallow penetration might result in production problems such as reaming of recess or excessive wear on driver bits.
Penetration gaging depth values for the various styles of recessed heads are included in the dimensional tables for the respective heads. These values were predicated originally on the gaging of plain finish (unplated or uncoa ted) screws. However, subsequent experience has shown that the Type I and Type 11 recess penetration limits as tabulated, and the Type IA and Type Ill recess penetration depths with the tabulated minimum limit reduced by up to 0.005 in., are suitable for the gaging of screws having coating thickness of up to and including 0.0003 in., on significant surfaces.
This allowance makes up for the loss of depth brought about by the plating buildup on the sides of the recess.
Screws having heavier coatings, which fail to meet minimum penetration, must be stripped of finish and gaged for acceptance or relection in the plain condition.
Specified in Tables Ill-I through 1114 are dimensions of gage points to be used for penetration gaging the Type 1, Type IA, Type 11, and Type LII recesses. These gage points approach as nearly as possible the perfect driver form. ALso specified are gage heads and bushings, which adapt the gage points to standard dial gages.
Penetration depths for Types I, IA, and 11 recesses are gaged relative to a reference plane defined by the intersection of the edge of the recess wings with the top surface of the screw head. This plane is the same as the top surface on flat head screws, but is somewhat below the topmost point on heads with rounded top surfaces. Knife edges or tapered ridges on the gage head are used to establish the reference plane.
Penetration depths or Type Ill recesses are gaged relative to a reference plane defined by the intersection of the edge of the recess square with the top surface of the screw head. This plane is the same as the top surface on flat head screws, but may be somewhat below the topmost point on heads with rounded top surfaces.
A reverse reading indicator is used to determine the penetration of the gage point into the recess. The gage may be zeroed on any flat surface.
111-2 FIT GAGING ON TYPE III RECESSES
In addition to the penetration gage, a “Fit” gage is also required for Type Ill recesses. Fit gage points are dimensioned in Table TTl-8. Fit is gaged by the insertion of the gage point into the recess, and a determination made as to how well the gage seats into the recess. The gage should produce a vety tight fit with the recess. This is sometimes referred to a “stick fil” A lack of this tight fit may indicate a problem with the shape of the recess.
the fit gage and the penetration gage combine to effectively determine the suitability of the Type III recess.