[How do I?] Copper Milling Tips

I

Iceman

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Its week two with the new PM-25 mill, and I have already worked with 1018 CR, and 6x and 7x Aluminium. I'm still feeling the machine out, but I already took on a small project making a bus bar for a PT-17 Boeing Stearman that I've been helping to build. Simple enough design, but now on to the questions.

I've read that copper is a nightmare, but so far I have been having very little issue following techniques similar to to milling aluminum. I'm actually working dry, with a 1/2" 2 flute TiAlN EM at 1500 RPM's. I have been working with a DOC of 0.10-0.20" and a fairly slow feed rate to attempt to produce a good surface finish.

Am I just getting lucky with the set up? Brand new sharp cutters I feel could be masking improper milling parameters/techniques. I don't have a lube/coolant mist set up yet - mostly because I'm worried about the mess (this is in my house) - so once I tackle containment, this will be next.

What tips does the group have on working with soft metals such as copper (in this case 110 copper).

In my hunt I have come across and interesting document, but feel like it is also kind of an argument to use copper as more of an everyday material.

http://copperalliance.org.uk/resource-library/machining-brass-copper-and-copper-alloys362

-IM
 
It all depends on the copper alloy. Some cut like butter and others will dull tools quicker that you would expect.
 
I can't say I have a lot of experience machining copper but I do remember that's it's like trying to machine chewing gum. Sharp cutters and cutting fluid of some sort will help with surface finish. Sounds like you are on right path.

Tom S.
 
I'm getting "crumble" chips - I'll post a pictures of where I am at. Maybe indicates too slow of a spindle speed. Doing my best to read the machine and material. I learn best by doing but research and experience from others goes a long way. No reason to reinvent the wheel.
 
milk works good for copper. You can not generate heat with copper, it turns to mush if you do, so light cuts and feeds, using some kind of coolant.
 
Not great pictures but it worked out fairly well taking small cuts. The finish is nigh mirror with minor tool marks still present - all in all first time milling copper I'm pleased. The part meets the functional requirements and at least to me looks good!
 
110 copper it really not the best to machine, looking forward to the steel parts I have coming up.
 
Absolutely beautiful finish on that copper part!

PS - I did a slight amount of machining on copper while a grad student many years ago, mainly drilling small diameter holes. On the advice of our machine shop folks, I used "lard oil." Without it, the drill bits would load up, and usually break.

I'm just not sure how/where you'd get lard oil cheaply. According to http://www.britannica.com/topic/lard-oil the oil is pressed out of the (rendered?) lard. But lard in the grocery store is pretty much a solid cake, possibly because it's been hydrogenated. Maybe melt the lard and mix with some other kind of oil?

McMaster-Carr does sell the oil, but it's kinda spendy ... http://www.mcmaster.com/#lard-oil/=127n9i1
 
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