Drilling copper

[davidwdyer]

I'm new here and not an expert so I need a little advice.
How do you drill deep holes in copper. I need to drill 3/16th holes to a depth of about one inch or more. The problem? I keep breaking drill bits. I know that I need to clear chips often, but should I use high speed, slow speed? Any information will be appreciated.

[wierdscience]

Coolant would be nice,copper transfers heat very rapidly,as it heats it expands,the chips in the drills flutes expand causing binding and all sorts of friction adding to the problem.

WD-40 will help,water soluable coolant would be better.

[Carld]

Low rpms help. Lots of lube. I use a 2 or 3 second plunge and retract method so the flutes don't get loaded.

[Mcgyver]

hi David welcome to the forum. textbook calls for a sharper point, 100 degrees for soft copper, but irrc I've managed with zero rake drills like you'd use for brass - its a pita regrinding points. then again i don't know how many you have to do. that and what weird said. unless you've got a very fast drill press, 3/16 is small enough that you could run at say 1500 or 2000 rpm in pretty much anything but slower doesn't hurt one bit and is probably a good idea.

sometimes on bronze, the material warming up and expanding tends to close in and clamp on the drill...a trick here is to grind one lip slightly wider so it drills slightly oversized. not sure if thats happening here or if the cutting edge is grabbing so figured you need the full arsenal!

[SGW]

I've heard that the old-time coolant/lubricant of choice for copper was...milk. I assume modern chemistry has come up with all sorts of custom compounds for the purpose since those days, but it might be worth a try. I assume you'd want whole milk, not skim.

[John Stevenson]

I used to make a lot of laser cutting nozzles at one time on a small capstan.
Used to run araound 1500 revs on most operations including drilling and used soluble oil but diluted about 4:1 instead of the normal 20:1.

This goes a lime green colour quite quickly.
Sharp drills, ground not black, good quality like Guhring and never had a lot of trouble. Any breakages were caused by tooling getting blunt.

This was all in 99% pure copper BTW which is a bitch to cut as it's so gummy.

.

[davidwdyer]

Hey, thanks a lot for your replies. I will try these recommendations out tomorrow.