What are the requirements for rounding and chamfering of the metric torx head machine screws?

Above the metric torx head machine screws fasteners in the metric system, we can see that there are rounding and chamfering. Their types are:

Its dimensions are as shown in the table below:

Unit: mm

Α is generally 45° or 30° or 60°. The rounding radius and chamfering dimensions of the metric torx head machine screws are marked according to the national standard GB 4458.4-84 “Mechanical Drawing Dimensions”.

In the above figure, we can see that the R angle can be used not only at the head but also at the joint between the head and the underside of the shank. In the metric, the R angle is used at the joint of the head and the stem of the metric torx head machine screws, which can make the screw not easy to break and play a protective role.

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