How to measure the roundness of the head diameter of the flat head socket head cap screw

Some of the heads made by the flat head socket head cap screw are not so round. When they are assembled on the product, they will not look so good. So, how do you measure the roundness of the head of a countersunk head hex screw?

There are 2 ways to measure the roundness of the head of a flat head socket head cap screw. The first method is to place the head of the screw fastener to be measured on the projector, and find the max concentric circle and the min concentric circle according to the actual contour line (see Fig. 1). The difference between the diameters of the two circles is determined value.

Fig. 1

Fig.2

The second method is to measure the diameter of four or more (see Figure 2) of the head of the flat head socket head cap screw measured by the outer diameter micrometer specified in GB/T 1216. The 1/2 of the difference between the Max value and the Min value is the measured value.

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