Drilling .09 thk SS

[Machine1]

Just another headache. I am running into problems with my .128 drill that I am using to drill thru 4 .09thk stacked Stainless Steel plates. It is drilling 56 holes and before it gets to the end the drill is breaking. I am running it at 1200rpm with a feed of 7.2. It equals out to .003 per tooth. I am chip breaking at .045". I am using a stub Cobalt drill. I would use carbide but we don't have any in house. Anyone have any suggestions.

[Rekd]

Can you hear it squeal? If so, you're not feeding it hard enough. Are the corners of the drill breaking/chipping? If so, you are either feeding too fast, or it's having problems getting between the sheets.

'Rekd

[Machine1]

Before I changed the feed and speed to what it is now...it would make it to the about the 7th hole and it would start squealing. Now since I changed the feed and speed it makes it thru about 50 holes and them starts the squealing... the tip of the drill didn't break down and the drill broke at the top by the holder.

[Rekd]

Originally posted by Machine1 Before I changed the feed and speed to what it is now...it would make it to the about the 7th hole and it would start squealing. Now since I changed the feed and speed it makes it thru about 50 holes and them starts the squealing... the tip of the drill didn't break down and the drill broke at the top by the holder.

Are you using standar twist drills? or parabolic? or split point?

You might try splitting the difference between the first feed/speed and the ones you're using now.

'Rekd

[Machine1]

Im using a split point 135 degree Cobalt Drill. I just didn't think that .003 chip load per tooth was that much.

[Rekd]

Originally posted by Machine1 Im using a split point 135 degree Cobalt Drill. I just didn't think that .003 chip load per tooth was that much.

.003 isn't too much for the right drill. I would try a standard twist drill, 118° tip. The 135° tips are for softer materials, like plastics and wood.

HTH

'Rekd

[Boss302]

Are you using a coolant?

[Machine1]

Flood...

[HuFlungDung]

I wonder if the "break-through" disk is what is breaking your drills? In mid stack, if one of these disks happens to get caught between the bottom of the hole and the bit, it effectively caps the cutting edges and snap!

I would try an even more acute angle to the drill, which should be of split point grind, in an effort to make sure it penetrates the next sheet before it has a chance to break out the "breakthrough disk" of the current sheet.

Maybe try not pecking at all, too.

[hardmill]

I'd bump to about 60 sfm .002 chip load and increase your peck.
Way too much engage/disengage going on.
jm2c

What kind of stainless is it?

PEACE

[Boss302]

Workhardening S.S.
R.P.M. 948 Feed 2.84 S.F.M. 32 Gives you a .003 chip.

Free machining S.S.
R.P.M 2132 Feed 6.4 S.F.M. 72 also a .003 chip.

Info. from CNCSpeed still one of the handiest software tools I've ever used.
Oh Ver. 5.9.28 gotta get the latest update.

[Machine1]

Where did you get the CNCSpeed software? Did you download it off of the net