For most tapping I do especially for small sizes I drill at least 0.1mm oversize. Usually 0.2mm and mostly tap on the mill with a guide to keep vertical. Rocol or similar RTD and a squirt of tapping fluid as well. I haven't broken a tap in the last 15 or 20 years. Edit, all my taps are HSS.
Edited By Chris Evans 6 on 01/09/2020 14:28:22