On Saturday, March 28, 2015 at 8:59:53 PM UTC-4, Terry Coombs wrote:


Carbide . You might get lucky and find a concrete drill that will open it up
to 17/64 , and they're cheap at the BBS's . I'd have gone to the desired
diameter in one step , Low speed and push it hard .

--
Snag

Carpenter Tech has a book on line about machining stainless steel. Lots of good information about drills for stainless drilling and what the angles should be. Also information about drilling to 4 or 5 diameters on the first go and then pulling the drill out to clear the chips. And then drilling a couple of more diameters and clearing the chips. And finally getting to where you only drill one diameter in depth and then clear the chips out.

Another tip is to use a center punch with a three sided end so you have less problems with the center punch work hardening the starting point.

And using a split point drill to minimize work hardening.

But what I thought was interesting is there was nothing about whether one should or should not drill a pilot hole. Other sites on the internet say drill a pilot hole. Maybe it is because Carpenter Tech says use a split point drill and the other sites say nothing about split point drills.

I personally am likely to drill a pilot hole a bit bigger than the web thickness of the drill used to complete the hole. It lets you feed the drill faster. So you might have some work hardening from drilling the pilot hole, but you can feed faster when drilling to final size. I might be influenced by the fact that I have some small diameter split point drill , but no large ( over 1/4 inch ) split point drills.

But I agree with low speed and lots of pressure.

Dan

wrote:
On Saturday, March 28, 2015 at 8:59:53 PM UTC-4, Terry Coombs wrote:


Carbide . You might get lucky and find a concrete drill that will
open it up to 17/64 , and they're cheap at the BBS's . I'd have
gone to the desired diameter in one step , Low speed and push it
hard .

-- Snag

Carpenter Tech has a book on line about machining stainless steel.
Lots of good information about drills for stainless drilling and what
the angles should be. Also information about drilling to 4 or 5
diameters on the first go and then pulling the drill out to clear the
chips. And then drilling a couple of more diameters and clearing the
chips. And finally getting to where you only drill one diameter in
depth and then clear the chips out.

Another tip is to use a center punch with a three sided end so you
have less problems with the center punch work hardening the
starting point.

And using a split point drill to minimize work hardening.

But what I thought was interesting is there was nothing about whether
one should or should not drill a pilot hole. Other sites on the
internet say drill a pilot hole. Maybe it is because Carpenter Tech
says use a split point drill and the other sites say nothing about
split point drills.

I personally am likely to drill a pilot hole a bit bigger than the
web thickness of the drill used to complete the hole. It lets you
feed the drill faster. So you might have some work hardening from
drilling the pilot hole, but you can feed faster when drilling to
final size. I might be influenced by the fact that I have some
small diameter split point drill , but no large ( over 1/4 inch )
split point drills.

But I agree with low speed and lots of pressure.

Dan

http://www.cartech.com/uploadedFiles...altyAlloys.pdf

--
Steve W.