How to measure the large diameter, medium diameter and small diameter of stainless steel socket cap screw?

Some customers are very concerned about the size of the screws of stainless steel hexagon socket screws or other screw fasteners. Once they do not meet their requirements, they will choose to return or the screw manufacturer to reproduce them exactly according to their requirements. For them, unqualified threads, they are not available. So how do you measure the large diameter, medium diameter, and small diameter of stainless steel socket cap screw?

The medium diameter and the small diameter of the external thread: the external threaded ring gauge conforming to GB/T 3934 shall be manually inserted into the external thread of the stainless steel socket cap screw and shall pass smoothly.

Single medium diameter of external thread of stainless steel socket cap screw: Screw the end thread ring gauge according to GB/T 3934 into the external thread of the workpiece by hand, but not more than 2 pitches (calculated from the ringback ring gauge).

There are two methods for measuring the large diameter of the external thread: the first method is to use the threaded ring gauge of the through and the end of the GB/T 3934, and the external thread of the workpiece is smoothed with the smooth end of the workpiece, and should pass smoothly; The external thread of the smooth caliper card workpiece should not pass. The second method is to use the micrometer specified in GB/T 1216 to measure in the two diameter directions perpendicular to each other at the test site.

Note: According to the provisions of GB/T 5267: the position of the thread tolerance band before plating is g or f or e; after plating, only the 6h or 8h thread pass gauge is used for inspection.

If it is judged that the thread gauge that is qualified is in compliance with GB/T 3934, the thread shall be judged as qualified.

Test site for large diameter: short gauge (l ≤ 5d) at 1/2 of the thread length; long gauge (l > 5d) at both ends of the thread, but should not be at the end of the thread and incomplete.

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