Yeah, Copper has a higher ductility & can be a problem with cutters which
have been ground for machining ferrous materials.
Excessive vibrations & digging are usually indicative of too much rake or clearance
behind the cutting edge. And sometimes of too high RPM and feed speed.
For copper alloys, as a general rule, the clearance behind the cutting edge should
be sufficeint to prevent a rubbing or burnishing action.
In other words, more of a shearing or scraping action than digging in.
I was taught in the 'old school' way where we had to grind our lathe bits
& mill cutters for each job. My teacher spent near as much time inspecting our chips
as he did with the part itself. Don't see much of that anymore.
Some of the younger CNC machinists I've spoke with in recent years have no idea
about bit/cutter grinding. They were taught to grab another pre-made one from
the shelf. Which is a real shame IMhO.
Back on track .......
If you have no way to regrind the cutters try slower RPM, feed speed, and
use a lot of soluable oil as coolant.
Cutting fluids with high lubricity should be avoided since they can cause the
cutting edges to slide over the work surface during the initial part of the cut.
At this point it would be interesting to note that with the proper cutter and
speeds, often no fluid is need at all. Depending on the work piece &
machining operation performed of course.
Hope that helps & wasn't too long winded.
