ISO 3439:1975

Subland twist drills with parallel shanks for holes prior to tapping screw threads

Lays down only metric dimensions, which are the only recommended dimensions in the future for these subland twist drills. The drills have been designed to produce holes prior to tapping metric threads over selected range of M 3 to M 14. Unless otherwise stated, these drills will be rigth-hand cutting. Supplements ISO 2306.