How does the flat head hex drive machine screw measure the perpendicularity of the top surface and the axis of the rod.

The flat head hex drive machine screw does not measure the verticality of the head and the stem as compared to other cup head and hex head screws. So what is the measurement method for this screw?

Method 1: Place the flat head hex drive machine screw to be measured on the V-frame specified in GB/T 1219 and turn it (no axial movement), and measure with the dial gauge specified in GB/T 1219. The maximum difference in pointer readings. see picture 1.

Method 2: Measure with a special inspection tool specified in GB/T 1219 with a collet and a dial gauge specified in GB/T 1219.

Method 3: Use the special angle ruler and feeler gauge specified in JB/T 8788 to measure the flat head hex drive machine screw.

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