Tapping screws belong to the thread-moulding screw family. When screwed into a pre-prepared core hole, these screws shape their own counter-thread.
Guideline values for selecting the correct core hole diameter are contained in DIN 7975.
Shape C = thread with tip
Shape F = Thread without tip
Shape R = Thread with rounded tip
Stainless steel tapping screws are weaker than case-hardening steel tapping screws. This means that these screws cannot form a counter thread in sheet steel. For this reason, they are used in soft materials such as aluminium only.