View Full Version : Runout, HSS drills and dowel holes

12-09-2016, 06:20 PM

Thank you for reading

I was taught that minimizing run-out is essential for successful drilling
I can see machinists making dowel holes with HSS drills in collets, and sometimes these drills run even more than 0.1mm out, on steel and aluminium.
I know the spot drill defines the position of the holes, however drilling with a drill which runs more than 0.1 out, I would not use it even to make a normal tapped hole for a high precision job
What’s your experience about run out

Thank you in advance for your support

08-03-2017, 10:24 AM
Relative to the job - 0.1mm is fine for a hole that is to be tapped, for dowel holes, they must be reamed to fit.

Drills are only ever treated as a way to get an approximate sized hole, the accuracy is added later by machining or reaming or boring etc.

If the spot-drill is used correctly then the drill can be quite bad and still drill in the correct place.

Robin Hewitt
08-03-2017, 11:36 AM
Collets come in different tolerances. If your vender does not mention tolerance you can probably assume they are from the cheap end of the pile :very_drunk: