Machining copper. Update.

I quoted a job for 100 metal parts for an automotive application, which is a outside of my normal routine. It was a gasket (injector gasket I think) designed as a powdered metal part. There were some small features on both sides of it. They wanted it quoted in 360 brass, and pure copper. I priced the brass parts a lot lower than the copper and kind of hoped I wouldn't see the copper part. I won the bid for copper.

I posted here on what was better to mill, 101 or 110 (my two choices) and received some good advice. So I ordered full hard 110. I used ZrN coated mills from Data Flute. Two flute carbide, high SFM, low depth of cut. Milling created burs, of course, but I used a finish pass (between .002 and .005) to mill away the burrs without creating much of a new one, and ordered the cutting sequences to minimize the number of burred edges and point the bur out, not in, so it they were exposed for tumbling. So the parts actually turned out extremely nice, with an iridescent mirror finish and very little burr.

I tried vibratory tumbling one in a light ceramic media, but the copper is so soft it just burnished the edges over and created a burr. So I ended up using an abrasive walnut shell I use for dry polishing aluminum, it provided a fine edge break and the parts look outstanding.

I used a 40,000 RPM air spindle for the 1/16 and 1/32 cutters which worked out extremely well.

The finished parts are dimensionally perfect with no chatter marks, galling or burs. With the proper feed, DOC, SFM and tool path strategy, pure copper mills very well.

Thanks to all who gave their input.

Reply to
Polymer Man
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Polymer Man,

Good of you to post your results.

Too often people drift off after getting advise from this group and don't post what their final outcome or resolution was.

Thanks, Tom

Reply to
brewertr

Polymer Man:

Now that's the kind of update and information that may help someone in the future, maybe ME! Thanks for taking the time to post it.

Reply to
BottleBob

=========== Thanks for the feedback. We all appreciate the "rest of the story."

Unka George (George McDuffee)

There is something to be said for government by a great aristocracy which has furnished leaders to the nation in peace and war for generations; even a democrat like myself must admit this. But there is absolutely nothing to be said for government by a plutocracy, for government by men very powerful in certain lines and gifted with the "money touch," but with ideals which in their essence are merely those of so many glorified pawnbrokers.

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Reply to
F. George McDuffee

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