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

Copper is very gummy.

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

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

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.

thanks, i'll try :wee:

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