Set out below are some guidelines for the application of tapping screws. The fastening methods shown are to be deemed as examples.

Tapping screws of Type B with cone end (also known as seekers) are the type predominantly used. This applies particularly when several sheets have to be fastened and hole mismatch is likely to arise.

Generally speaking, tapping screws of Type BZ with flat end are preferred only when the end of the screw is exposed and the cone end of type B would present the risk of injury.

With plain fastenings, that is to say fastenings in which the tapping screw cuts its own mating thread it is necessary that the total thickness of the sheets to be fastened should be greater than the pitch of the thread. If the total sheet thickness is less than this, it is best to pierce the core holes. In this way the necessary tightening effect can be ensured. Alternatively, the use of speed nuts is recommended.

In many cases, too – particularly in mass production – there are advantages in using what are termed pressed hole fastenings. By the use of a special tool the hole is punched, slotted and given a spiral form corresponding to the pitch of the tapping screw used. The hole may be made only in the sheets to be fastened or additionally in an extra sheet in a manner similar to the speed nut. Pressed hole fastenings are generally recommended only for low carbon steel sheet. Heat treated steels and nonferrous metals sometimes require specially designed holes.