Re: Carbide counterbore

Dave Mucha

--- In, nwinblad@... wrote:

Does anyone know where I can buy a carbide step drill or counterbore
for 4-40 pan head screws. I need to put some screws into a hardened
steel gear. I can't seem to find a carbide step drill anywhere. I
tried drilling through this stuff with a cobalt drill and it wouldn't
touch it. Then I chucked up a carbide drill and it goes through it
nicely. Now I just need to find a supplier...

What i do on holes that are deep enough is to drill the hole with a
regular drill, then once the hole is there with walls, finish the
bottom with an endmill.

Sometimes it works great, sometimes it don't. last set was of 8 holes
and half would up with chatter on the side walls. but the hole was
over an inch deep.

I find that if I clamp the part, drill, then switch to the end mill ,
it does a good job. when I drill all the holes first, then go back is
when I have problems.



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