Drilling Stainless Steel

mopowers said

Well, It turns out the Grainger near my house sells Tap Magic cutting oil. I'm going to pick some up today after work.

I've got a couple 1/4-20 taps. I'm not quite sure if they're HSS, but they're older American made taps. I'll look at them closer and see if they say HSS. Is there another way to find out?

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It might be stamped (etched) on the tap but I don't think I've ever seen a tap (designed to tap threads in metal) that was not HSS. There are even stronger more higher quality taps but HSS should work just fine if you use Tap Magic and you go slow. Remember that the material a tap is made out of is brittle (very, very hard). If you accidentally dropped the tap onto concrete it could break. So be sure to keep the pressure directly along the axis of the tap (no side to side stress) or it will snap off!! If you try and tap too deep without backing up it will snap.
Good Luck

Gil