The joys of Copper

[rleete]

• Not enough frustration in your life?
• Parts being made too quickly?
• Not enough broken tools?
• Tolerances too easy to hit?

Try machining copper!

All the worst qualities of plastics, but hard enough to grab, so you can't take a cut more than .002"
More time in the shop, away from family and in-laws - especially important in the holiday season
You can snap off drills - for that all important excuse to go to the hardware store
Chatter & squeal enough to make all the neighborhood dogs howl
Lousy finish cuts means more time polishing, and you'll have a foolproof way of discovering which of your cutting tools has a less than perfect edge

Cheapskate that I am, I decided to grab a couple of pieces of 1.5" copper from the scrap bin. Masochist that I am, I decided they'd make good flywheels, with my limited machining experience. As you can see, the finish needs a bit of work. You can also see the marks in the edge from the chuck; don't tighten it down enough, and you can have it spin right out when the tool grabs.

Crisco shortening was used as a lube (tip from minilathe forum), and the tool was a carbide bit. I had the tool sharpened by one of the diamond machinists at work, so it was about as perfect as it's ever gonna get. Cuts were light - .002 or less, and I cranked the crossfeed handwheel slowly. Still, it chattered, and the surface is covered in microscopic burrs (what looks like dust in the pic). Took me all afternoon to do this one piece, both sides.

It does have the redeeming quality of having considerable heft for it's size, so should function quite well.

 

[Metal Mickey]

I couldn't agree more! I am playing with the stuff at the moment (see Fowler ash pan post). It's 'orrible!

 

[rake60]

The first time I machined copper was a disaster!

I used a standard carbide insert at the speed and feed I'd always used on steel.
The copper globbed up on the tool and the stock spun loose in the jaws.
I was shocked by the ball of copper that was sticking on the tool and reached in
to pull it off. Bad Move! :-[ After the smoke stopped flying from my fingers I
replaced the insert with a sharpened positive rake and it cut fine.
It produced a wicked stringer chip to be managed, but I found out how to cut it.

Rick

 

[Brian Rupnow]

My son, you are singing to the choir!!! I had a big peice of pure copper plate, 8" x 3/4" x 21" that I salvaged from an automatic welding station that I redesigned a few years ago. I have used it as the base for a steam engine and for a slinky machine, and I agree----the damn stuff is horrible to machine!!

 

[rake60]

It doesn't necessarily have to be a horrible metal to machine.
It just requires a different approach.

Copper is gummy as hell.
It will stick to the tooling as well as to it's self.

Machining copper does requires a certain level of finesse.
Once you figure out just what the material wants, it's no tougher to
machine than aluminum. It's a whole new game!
Old proven tactics do not apply when working with gummy materials.

Use very sharp, positive rake tools, higher than normal surface speeds
and it will cut just fine.

Rick

 

[jack404]

copper

SHUDDER

thanks for the tip Rick but i do try to dodge it unless really nessecary

 

[joeby]

Copper is one of those materials that you can't "push" off, you have to cut it. Stainless is kinda that way too. A turning tool ground for steel won't work too well. I have some tools that I've ground a groove along the cutting edge, kind of like a chip breaker. I just used a Dremel with a small "drum" wheel on it and ground a groove deep enough to make a knife edge. That will also make the chip into a tight curl. I needed to make some EDM electrodes .007 dia. for a job at work. Using a tool ground with a groove in it, I turned them from 3/8 stock in one pass about 3/16 long.

Kevin