In forming tap processing, the material is displaced by plastic deformation, resulting in a raised shape (burr) at the hole entrance.
To suppress these burrs, it is effective to perform a chamfer of 60°~70° (included angle) on the pilot hole advance.

hole entrance End face, without chamfering

A: Pilot hole diameter B: Burr

hole entrance End face, chamfered case

A: Pilot hole diameter B: Outer diameter of screw

Notes:
There are two ways to express angles in the catalog: Point Angle (included angle) and Taper Half-Angle.

Example: Point angle 90° = Half-angle 45°. Both refer to the same tool geometry. 

When a 60° to 70° chamfer is recommended for a forming tap pilot hole, select a chamfering tool with a 60° point angle.