Thread mills are unique in their cutting action because not only the cutting edge is working but also the flanks and, maybe even the minor diameter will be cutting. Additionally the two flanks are under different pressure, because we also feed with pitch per revolution. Because of the radial and axial forces which result simultaneously, a rigid tool holder with very good concentricity is required.

A precision endmill holder with side clamping screw is recommended, but because the applied clamping pressure from the screw is one-sided, it is possible that concentricity problems can occur due to enlargement and wear of the bore on a used holder. Therefore, before using a thread milling cutter, it is advisable to check the eccentricity of the holder, which should not be more than 1/5 of the feed per tooth value. Hydraulic chucks and shrink fit holders are also suitable for the thread milling process.

We do not recommend the use of ER collet chucks. This type of tool holder can cause solid carbide thread mills to chip or break prematurely.