Hard and Slow: Drilling Stainless Steel


I’ve been to Pick-a-Part, to scavenge some replacement wing mirrors for my Subaru Legacy. 100% success on that front. Also grabbed some more VW seat belts to add 3 more buckles to our key holder.

Pick-a-Part, Mangere. Great afternoon out, for $2

Drilling the holes on the first four clasps caused me no end of problems. They are some sort of stainless steel and are magnetic so a ferritic alloy. I was using a cobalt bit but as pretty much as soon as I started progress would stop since the stainless steel work hardens and becomes impenetrable. I eventually ‘won’ by punching out the holes: I hit it with a hammer.

I came across this article from sail magazine some time ago and decided to give it go on the 3 new clasps.

The advice in the article worked.

In summary. If you are drilling stainless steel:

  • Nice sharp bit (apparently can be HSS, but I used cobalt)
  • Slow, (and patient)! Slow as in 3-5 revs/sec. I used a hand drill as my drill press does not do S-L-O-W. There seems to be a sweet spot where you can feel the bit cutting.
  • Pressure. As much as you can muster and your bit can take. I had my whole weight on the drill. A press would a better option.