drilling copper

[jeremyinnys]

i've been having problems at times drilling some holes in copper. i got some 110 electrolyte copper, and i need a bunch of .160 holes in it. right now i'm at 1525 rpm, and a feed of 3.5 ipm. i've tried both straight drilling, and now peck driiling, but i still have problems with drills breaking. the copper is 1/2" thick and i need to go thru it with hss .160 drill. any suggestions. it doesn't happen with every part, but enough where i can't use the part because if i don't hear it break it tries to drill without a point, and ruins the part. thanks for any help.

hardinge vmc 1000

[Rekd]

Copper is very gummy.

Try increasing the chip load, peck drill, and use lots of coolant.

[mxtras]

Flatten the face of each flute with a small facet - this will keep it from grabbing by creating a neutral face angle. Positive rake angles dig while neutral angles push.

Scott

[Rekd]

Originally Posted by mxtras Flatten the face of each flute with a small facet - this will keep it from grabbing by creating a neutral face angle. Positive rake angles dig while neutral angles push. Scott

Good idea.

Also consider using 135° vs 117° drills. Steeper angles work better in softer mat'ls.

[jeremyinnys]

thanks, i'll try

[stupidog]

We have a lot of success (1/16" diameter drills) using 135 degree Guhring polished parabolic drills. Use straight oil, not soluble.

[myob]

try drilling at 300 to 450 rpm and use cow's milk as a coolant.

[Ed from NY]

Chances are the chips are not clearing.

+1 on the coolant. Try doing a full retract pecking (so that the chips get brought out and the coolant gets in) and keeping the peck depth between 2/3 and 1/2 the bit diameter (so that not too much accumulates). Once it is all working reliably you can try to squeeze some time back. The RPM and IPM seem to be okay, if anything I would bump the RPM to 1660 (70 sfpm).

Good luck!

[underthetire]

I hate it, but...
Every shop I used to go in to that did almost all copper, used cutting oil, not coolant. I used to machine a lot of OFHC and it was all done with oil as well.

[neilw20]

Cutting oil.