Enlighten me on copper

I've been doing lots of research on machining copper in advance of a project and while I can't speak from personal experience, I can regurgitate what I've read in forums and from tooling manufacturers.
For your tool You want:
very sharp
Very pointy
High positive rake
Abrasion resistant.
diamond/PCD specifically designed for copper = best.
diamond/PCD designed for nonferrous metals = good
Carbide inserts designed for nonferrous metals or hand-ground Carbide of the proper geometry = ok
Generic diamond/PCD = somewhere between ok and crap
HSS hand-ground to the proper geometry = ok for a few minutes, then crap
Generic Carbide or HSS = crap

Use lubrication/coolant
Start with feeds & speeds for aluminum and adjust as necessary. There is also a document on machining copper from copper.org, but since the variants of copper machine so differently from each other and the cutter makes such a difference, the info is pretty vague

Those inserts for nonferrous and specifically for copper are hard to find and expensive. I've bought some from ebay, what I could I could find, and then bought insert holders to match what I was able to get. I haven't used them yet.

There are "free machining" coppers (ex: C14500 tellurium copper, and sulfured and leaded coppers) that are much less of a pain than pure copper. If you're not restricted to the exact type, check those out. You can buy c14500 from Saturn industries, that was the most reasonable pricing I found online. You may be able to find it cheaper from a local supplier.
 
I used to turn copper electrodes for sinker EDM use... surface finish was very important. I used HSS... ground very sharp with just a slight amount of relief... and NO nose radius. I remember I always spun it at 550 RPMs, but don't remember DOC or feed rates.

That has been a good many years ago...

-Bear
 
It seems as I feared....I need to use HSS. I'd love the PCD, but have no idea where to get it, what tool holders, and if they even make them for a 10" swing (tool size limitations.)
 
I've had some limited experience with copper, and also talked with some machinists. The "hot setup" seems to be to use lard (or lard oil?) as a cutting fluid. I use a mixture of lard and kerosene as an aluminum cutting lubricant, and I suppose it would work OK. +1 on very sharp HSS cutting tools.
 
Man! Are you worried about an infest of bugs on your machine chowing down on the lard? Maybe I should make my heatsinks out of aluminum...
I'll have to dig out my HSS and give it a shot. The CRC sulphur lube is pretty damn great...but it will stain metal if not cleaned up right away. Better than bugs moving in!
 
GunsOfNavarone said:
It seems as I feared....I need to use HSS. I'd love the PCD, but have no idea where to get it, what tool holders, and if they even make them for a 10" swing (tool size limitations.)
Click to expand...
They make em small.

Here are the smallest of the random smattering of PCD inserts I bought.


Screenshot_20210202-233751_eBay.jpg



The listing says carbide but they're not; they're PCD. Probably why they were so cheap; seller didn't know what they were selling.

They are sized the same as 1/4" indexable insert tooling like you would use on a sherline/taig or a HF 7" mini lathe but the holes are too big for the screws those use. I'll have to figure out something else.

Note the MD220 grade, that's a good buzzword to use if you're looking for copper cutting inserts.

If you're only cutting a few parts HSS should work well enough. I went for the PCD because I hopento go into production with this.
 
OMG, I forgot, James Cagney could tell you all about coppers.... :grin:
 
It sounds like honed inserts like those sold for aluminum might work well for you if you don't want to grind HSS. If nothing else they are easier to find and cheaper than PCD.
 
ttabbal said:
It sounds like honed inserts like those sold for aluminum might work well for you if you don't want to grind HSS. If nothing else they are easier to find and cheaper than PCD.
Click to expand...
This is the second time I’ve been nudged towards PCD. If I can find them in my lil’ insert sizes, I’m on it. Between stainless and titanium...it’s all covered.
 
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