We are having a problem drilling some 440C stainless steel. Anyway we
are drilling 1/8" holes 1/4" deep. We have been using high speed steel
and been averaging around 75 holes per operation before the drill bit
needed to be changed. However now we are lucky to get 2 or 5 holes
before the drill bit needs to be changed. We had a cobalt drill and
tried it with the same problems. We checked for hardness which we got
Rockwell 35. Which was wierd So we tried file test which was 55-60. I
am thinking that it might be a chromium issue but not sure.

Does anyone have any suggestions on what I might try or what might be
the problem and how I might fix it?

Any suggestion will be helpful!

On 9 Feb 2005 16:15:00 -0800, "Chopster"
wrote:

We are having a problem drilling some 440C stainless steel. Anyway we
are drilling 1/8" holes 1/4" deep. We have been using high speed steel
and been averaging around 75 holes per operation before the drill bit
needed to be changed. However now we are lucky to get 2 or 5 holes
before the drill bit needs to be changed. We had a cobalt drill and
tried it with the same problems. We checked for hardness which we got
Rockwell 35. Which was wierd So we tried file test which was 55-60. I
am thinking that it might be a chromium issue but not sure.

Does anyone have any suggestions on what I might try or what might be
the problem and how I might fix it?

Any suggestion will be helpful!

ask over on alt.machines.cnc.

They will be able to give you chapter and verse.
Btw..there are some point angle geometries which will help out a lot.
And split point is de regure for production 440c

Gunner

Rule #35
"That which does not kill you,
has made a huge tactical error"

We are having a problem drilling some 440C stainless steel. Anyway we
are drilling 1/8" holes 1/4" deep. We have been using high speed steel
and been averaging around 75 holes per operation before the drill bit
needed to be changed. However now we are lucky to get 2 or 5 holes
before the drill bit needs to be changed. We had a cobalt drill and
tried it with the same problems. We checked for hardness which we got
Rockwell 35. Which was wierd So we tried file test which was 55-60. I
am thinking that it might be a chromium issue but not sure.

Does anyone have any suggestions on what I might try or what might be
the problem and how I might fix it?

Any suggestion will be helpful!

How many parts total are you doing?

Are you using liquid coolant? Try tunning around 1500 RPM or less and use
coolant. Coolant with stainless is an absolute must in most cases. Did I
mention coolant? Even cheap motor oil will help quite a bit. Just use some
no mater what. Each revolution should be around .002" feed and the thrust
around 100 lbs to accomplish this if you don't have an auto feed or
programmable system.

If you are doing this already and your RPMs are at least 1500 or less, then
there may be a different problem but we need more info to diagnose. 1500 is
the maximum RPM I'd suggest to a customer without coolant.

With coolant and a low enough RPM rate, you should get 1000 holes per bit.


Free drill RPM and feed chart he
http://www.multi-drill.com/drill-speed-chart.htm

Regards,
Joe Agro, Jr.
http://www.autodrill.com
http://www.multi-drill.com

V8013

My eBay: http://tinyurl.com/3n8gj

The 440 will work harden if you feed too slow and let it get too hot.
Instead of peck drilling, try going all the way through with continuous
feed and coolant. That way the bit is cutting unhardened material and
you should have better results.

Chopster wrote:

We are having a problem drilling some 440C stainless steel. Anyway we
are drilling 1/8" holes 1/4" deep. We have been using high speed steel
and been averaging around 75 holes per operation before the drill bit
needed to be changed. However now we are lucky to get 2 or 5 holes
before the drill bit needs to be changed. We had a cobalt drill and
tried it with the same problems. We checked for hardness which we got
Rockwell 35. Which was wierd So we tried file test which was 55-60. I
am thinking that it might be a chromium issue but not sure.

Does anyone have any suggestions on what I might try or what might be
the problem and how I might fix it?

Any suggestion will be helpful!