Even among experienced machinists, choosing the right insert for boring a hole remains a difficult process that is fraught with myth and misconception. However, it is no myth that insert selection can completely save or kill performance on an application.
A pilot or spot drill, also known as a starter drill, is typically required when the succeeding drill is longer than 10xD or smaller than Ø 1.00 mm. Starter drills can also be used to improve hole location due to their short, rigid geometries.
There’s more than one way to finish a hole. The most effective option will depend on the number of parts, acceptable cycle time and tolerance callouts.