What is ... the clamp thickness?

What is clamp thickness and how is it calculated for self-drilling screws?

In short, the clamp thickness is the area of a self-drilling screw which can be used to connect two components. It is thus the area of a screw which can absorb and carry load.

How is the clamp thickness calculated?

If you approach the subject a little bit unsuspiciously, you could come to the conclusion that the clamping thickness of a self-drilling screw is quite easy to determine from the length of the screw. Hence, the clamp thickness is the threaded part of a screw minus the length of the drill point, right?

Wrong! Especially with regard to the clamp thickness of self-drilling screws, there are some important points to note:

1. Clamp thickness and thread turns:

If you have a closer look, it is relatively easy to understand that the first thread turn of a self-drilling screw is only suitable for clamping to a limited extent. Much more important, however, is the second point which is especially valid for self-drilling screws for weater-exposed areas (JT3).

2. Hardened drill points:

JT3 stainless steel screws feature a drill point made of steel - for strength reasons, therefore they are called "bi-met screws"! But in weather-exposed areas, only the stainless steel part of a screw may be used for clamping. And for this reason, the indicated clamp thickness must be considered especially when stainless steel self-drilling screws are used!

Which mistake can be made during processing with regard to the clamp thickness?

With regard to the clamp thickness, you actually cannot go wrong. It is important that you observe the clamp thickness values stated in the EJOT catalogue. The clamp thicknesses were thoroughly calculated by the EJOT application engineering based on the approval. The EJOT online shop also clearly displays the clamp thicknesses. Here, you can additionally search for a clamp thickness range when selecting a self-drilling screw.