Getting a good finish turning copper

[Warpspeed]

I am about to start fabricating some oil cooled electronic heatsinks for an induction heating furnace project (featured in another thread here).

These will be assembled out of various pieces of fairly thick copper, and silver soldered. No doubt the whole thing will end up covered with scale and probably become distorted with heat by the time I am finished.

I will then need to true up one face in a lathe, but lathe work is not my area of expertise. Any expert advice as to speeds, feeds, lubricant and preparing a suitable tool to do this on soft annealed copper would be greatly appreciated.

[Frank GP]

My experience with Copper is largely turning the commutators on rewound electric motors. I started with the textbook 20 plus degrees of top rake and about 10 degrees of side and front clearance with limited success. I found that the key was the surface speed, do not run too fast and do not take too big a cut. Due to the nature of the work we tried to avoid lubricant but did not find it too much of a problem. The composition of the commutator materials varied so much there seemed to be no hard and fast rules. Hope this has been helpful even though I have not really told you a great deal. P.S. as my old boss used to say when you were struggling: - "Well, if you can't make it size, at least make it shiny!" Best Regards - Frank

[Warpspeed]

Thanks for the help Frank. I have been experimenting, and agree that very fine cuts with a sharply pointed (non radius) tool seems to give the best results.

Cheers, Tony.

[Frank GP]

Glad to help.

Best Regards
Frank

[g-codeguy]

Originally Posted by Warpspeed Thanks for the help Frank. I have been experimenting, and agree that very fine cuts with a sharply pointed (non radius) tool seems to give the best results. Cheers, Tony.

No experience with machining copper, but have used tools with no radius. I am surprised they give you the best finish. Past experience has shown that even a .002R gives a much better finish. I do agree the sharper, the better on soft materials.

[RICHARD ZASTROW]

Used to turn copper printing cylinders. Machining copper is like cutting cheddar cheese with a knife, it globs up sticking to the tool. Don't laugh now. We switched to poly-crystal diamond tipped insert. The cure was to spray PAM fry pan stuff on the tool tip and workpiece. Continuous chip came off like a perfectly flat piece of Christmas tree tinsel. When the copper "tinsel" started to flutter and wrinkle, re-applied PAM. Chip went back to flat no-flutter. Turned full width (80") of roll non-stop chip. It might require polish to remove discoloration. We didn't, this operation was followed up by superfinishing.