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Milling copper rings with a rotary table.

Hinton184

Hinton184

Plastic
Joined
Sep 7, 2012
Location
Akron, Ohio
I recently received a RFQ for a small job cutting some copper rings in my shop. Some of them are small enough in diameter to fit on my lathe which I think is the ideal process to machine them. However, some are quite large and I don't have a big enough swing to cut them. My lathe is only 10" swing and much less over the carriage.

I have a milling machine equipped with a DRO system and a 12" diameter rotary table, so something I considered was getting copper sheets or blanks as flat stock and cutting them on the rotary table. Fortunately the rings come in various diameters anywhere from 6-12", so I have the capability to make 3 or 4 rings out of a sheet of 12" square blank and not waste a bunch of material. :)

Does anyone have any experience or advice to give here? I know copper can be a pain to cut sometimes so I'm wondering if I will run into issues with speeds and feeds trying to cut the diameters by spinning my RT.

Thanks,

TS
 
KMoffett said:
What type copper? Some series don't machine well at all. Probably more than you want to know, but might help:

https://www.kupferinstitut.de/fileadmin/user_upload/kupferinstitut.de/de/Documents/Shop/Verlag/Downloads/Verarbeitung/i018e.pdf

Ken
Click to expand...

+ 1, ..........That's the biggest stumbling block with copper.

Next Q - what thickness are these rings? ........any help offered will really ;) depend on more information, .......PS, we don't want to know what they're for, just sizes and spec etc etc etc.
 
Limy Sami said:
+ 1, ..........That's the biggest stumbling block with copper.

Next Q - what thickness are these rings? ........any help offered will really ;) depend on more information, .......PS, we don't want to know what they're for, just sizes and spec etc etc etc.
Click to expand...

Material is C 11000 Electrolytic Tough Pitch and unfortunately I cannot water jet them because of the specs on the print requiring they have to be machined or stamped.

These parts are all 3/16" in thickness so that makes it nice if I can buy a sheet already to size on the thickness. All tolerances are also +/- .005 on diameters and concentricity so that makes it easy to work with.

I am no seasoned machinist by any means, so any advice on feeds, speeds, setup, coolant, and tooling would be appreciated!

I am thinking HSS end mill either 1/4 or 3/8" diameter 2 flute. Crank my mill as high as it goes on RPM, and go somewhere between .030-.060 DOC.
 
Hinton184 said:
Material is C 11000 Electrolytic Tough Pitch and unfortunately I cannot water jet them because of the specs on the print requiring they have to be machined or stamped.
Click to expand...

Why isn't a waterjet machining? I think you're making a mistake trying to do these with what you have.
 
Even if the finish doesn't work for waterjet, you can still get blanks cut with some stock left for cleanup on your mill/RT or lathe. There's much less waste due to the thin kerf of waterjet, and the possibility to nest closer together.
 
Imagine cutting something akin to buble gum, IMHO you need to machine some copper to understand, its a very unique experience, personally i rather cut 304 stainless.
 
Old school coolant is milk.

Cost-in a replacement rotab; you'll destroy it with that sort of use. Others have driven a rotab with a drill motor with Bad Results.
 
Another old school cutting lube is kerosene ... or if you don't like the smell, unscented lamp oil.
Have material waterjet cut leaving a little stock, and don't run you mill wide open. Figure about 150 sfm and full depth cut at finish diameter.
 
Garwood said:
Why isn't a waterjet machining? I think you're making a mistake trying to do these with what you have.
Click to expand...

Indeed. The person who did the drawing may not even know what water jetting is. If they spec stamping they must not be expecting phenomenal accuracy. Having said that, if these were knife edge seals for high vacuum, you'd want the inside of the ring to be quite smooth so as to be easy to clean. It wouldn't have to be very accurate though so you could hand finish from waterjet and you'd still be ahead of manual machining.

Also, if you have small and large ones you could waterjet a bunch concentric, so as to minimize waste.
 
SteveBausch said:
Cost-in a replacement rotab; you'll destroy it with that sort of use. Others have driven a rotab with a drill motor with Bad Results.
Click to expand...

I've cobbled a DC gearmotor onto my 12" for work like this, it doesn't seem worse for the wear. I do try and turn it "backwards" in order to put the worst wear on the normally unused side of the worm and gear.
 
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