On Thu, 30 Aug 2012 21:58:28 -0400, john wrote:

wrote:
On Thu, 30 Aug 2012 19:59:34 -0500, Tim Wescott
wrote:

I may have asked this before, but I'm slow:

I have some 304 sheet. I use it to make control-line model airplane
handles. Each handle needs to have about 20 1/16" or .050" holes
drilled in it, in a pair of tidy lines.

This stuff breaks my regular old HSS drill bits, and my drill hand-
sharpening mojo is pretty spotty at 1/16".

I'm using them in a drill press. The whole process feels weird -- it
feels like there's a skin on the metal which prevents the drill from
starting to cut unless I feed it fairly hard, but once broken through
doesn't cause much problem. Most of the time that I break a drill bit
it's because I'm feeding it "just a bit harder", then SPING -- I've
broken another bit.

Is there a better drill bit to use, or have I just doomed myself to
trouble? Is there a better flavor of _stainless_ to use? I
understand that 304 is difficult to work with, but it's what McMaster
had in the thickness I wanted; having experienced its joys, however,
I'm ready to consider something else.

I think my next step is to get a dozen 1/16" drill bits, but if
there's some magic material that'll help here, I'm listening.
Any reason not to use 6061T6 aluminum instead??? If you NEED to use
stainless, you will NEED a better drill bit. With stainless you need a
POSITIVE feed - never let the bit skate on the surface. I'd try a good
center punch - or use a "center drill" to make the starting dimple,
then follow through with the normal bit. Get one of those that they
show at tradeshows etc drilling through files and leaf springs, and
using them as milling cutters.



303 stainless will machine and drill much better because of the sulfur
content of the metal. The bad part is that 303 doesn't weld well
because of the sulfur content.

McMaster doesn't carry it, but I suppose that means I should just look
around.

--
Tim Wescott
Control system and signal processing consulting
www.wescottdesign.com