The Cyclus Tools Threader Professional for BSA (1,370" x 24 tpi) produces optimal concentricity of the bottom bracket thread. Insert both sides of the threader simultaneously to prevent it from canting.
Use of a suitable cutting oil is necessary.
Attention: letters and marks on the tool refer to the tool itself, not the frame. For example, “R” means turn the tool to the right, and “L” means turn it to the left.