copper woes

rhrocker

rhrocker

Joined
Jan 18, 2004
Messages
1,135
I keep breaking off 1/8" bits in a bar of 1/2" thick copper I'm drilling for a guard (No anti copper comments please :D ) I'm I hardening this stuff by just drilling it? Whatever the case, I need to anneal the bar and would like to know how you guys do it.
Many thanks.
 
Copper is annealed by heating to red and then quenching (water), it is the opposite of tool steel. It is so "gummy" that doing anything to it except cold hammering is tough. The only way that I have been able to drill it is in short pulses and keeping the bit clear of cuttings with each pulse (PITA!).
 
Copper and it's alloys start to anneal at about 450 F .Easier to heat it to red and cool [quenching in water does nothing except cool it quicker !] Use sharp bits , don't baby it , clear the chips.
 
I had trouble (breaking 1/16" cobalt bits) in a piece of copper a while back. foound out you have to go in just a touch and then back out, then do it over and over, apparently copper is real gummy and will trap your bit and break it quickly. Also i t was suggested to touch the very tip of the bit to a belt sander or grinder to make just the very point part flat. It worked great. Just remember, in and out a lot and clear the long strands from the bit. I had some strands ofer 3" long :eek: .
 
While the advice on annealing non ferrous metals is certainly good to know, hardness ain't your problem.

The bits are grabbing and breaking because of copper's "sticky" or gummy quality, as mentioned above. Silver is the same way. To prevent this you need lubrication. (actually, not so much lubrication as a barrier between the metals.) In my fine metals classes, we were taught to keep some wax (Surely your wife has plenty of scented candles- she'll never miss one!) handy and just rub it on the spinning drill bit before lowering it to the metal. You gotta keep backing the bit out and reapplying it to the tip & sides of the bit. Since this way is less messy than oil, it's all I've used, but if you're more accustomed to oil or cutting fluid, I suppose that should work just as well. It's always a good idea to keep the chips cleared, but as long as you lubricate they should not be a problem. I've never had any reason to grind the tips off my bits this way.
 
I have also used a little graphite powder on the bits on sticky metals with good success. But alot of people don't have that in thier shops (but should).
 
Ok, thanks. Also, I wanted to mention this, just before the bit shatters (usually several small pieces), the bit makes a crackling sound like it's drilling through glass. It's a very distinct sound, then......snap goes the bit. So perhaps I am getting to much drilling debre all stuffed down around the bit. I'll try several of the suggestions tomorrow and see if I can find one or more that helps. Lube seems to be the key, although I can't help but think this stuff is hardened in what feels like layers or something.
 
Copper can be difficult to work with. Old time machinists recommend milk as the best cutting fluid-- seriously. I've used it and it seems to work better than any of the commercial cutting fluids I've tried.

George
 
I guess that'd have to be whole raw milk, ha-ha. How interesting, I'll have to try that. We always used a solid wax-like lubricant shaped like a cone or a pop-up cylinder (like under-arm deoderant) for fine drilling or sawing with thin jeweler's blades. Can get it from most jewelry suppliers.
 
One other thing that works for soft, non-ferrous metals is to use a DULL drill bit. The reason you're breaking bits is that they are cutting to quickly and getting stuck because they want to feed down into the soft material too fast. Break out those old, dull bits and it'll go a lot easier.

-d
 
reduce the rpm too and feed slowly. "peck" at the copper, avoid those long twirly shavings. Lubricant/coolant is essential.
Good luck,

Mike.
 
Wax works very good as a lube for soft gummy metals, I have also had good luck with Ivory soap, both in bar and liquid form. One commercial lube that I feel is underrated is Anchorlube, it is a soap based lube, not oil. It works great on most of the metals I have worked with, cleans up with water and a rag, and doesn't create toxic fumes when heated.
Ken
 
As said above, wax works very good in copper. I use a wax lube from MSC for drilling and tapping, Burr-life is also good stuff.
 
Thanks everyone. I have enough suggestions here to last me a lifetime! Sure appreciate the comments.
 
Alos a non conventional method that woorks well for me is shot tap into the coppet, very light pressure, but with high rpm. the maall the bit the higher the RPM, In this method, the chips will self clean, wax and or soap will help a lot. Mike http://www.lovettknives.com/
 
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