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Turning Aluminum in my CNC mill....

Joe T.

Cast Iron
Joined
Jan 29, 2008
Location
NY
I have yet another reoccurring job that I would normally do in my lathe. I reface snowmobile clutches for a race shop down the road from me. This requires me to set the compound in the lathe to a specific angle. The turning is done all by hand as my power feed can only go one direction at a time. There are chatter issues as well.

I decided to put my CNC mill to work on the project. Using a spiral routine I was able to mill the first clutch half. To get the desired finish took 290 revolutions @ 30 ipm. As you could speculate a 12” diameter takes TOO long using this method. I was able to leave it unattended the whole time if there had to be a good side to the story.

I decided to take a backwards approach to this problem. I made up a face plate out of a Ford nodular iron flywheel. Mounted it to an R8- boring head mandrel, attached some acme rod to the center, mounted the clutch in the spindle and put the tool bit in the vise. This worked out very nice and cut the cycle time down to minutes. No chatter issues either. I have to take about .093 off the face so it takes several cycles. When the end mill was cutting all I had were chips. Plus I could take big bites. Now that a tool bit is cutting like in the lathe I have a huge bird nest building up on the tool.

What can be done to break the strands of aluminum? I would like to walk away and come back to a finished job. As it stands now I fear this giant wooly monster tangling up everything.
 
Get a proper insert with a good chipbreaker made for aluminum, or try a mechanical chipbreaker. Call your tool rep and tell 'em what d.o.c. and feed you are running to get a proper tool form.
 
This is the setup. I have a tool holder that takes an insert that is about .875 wide. This was something I bought on sale probably 10 years ago. I don't recall nor can I read the part # now.

I tried lifting the work piece off the tool every .750" then doing a back cut as the finish cut. This did little to resolve my bird nest problem. It did leave a nice finish however.

Looks like I will have to research chip breaker style inserts.
 

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That looks like a very common triangle negative rake insert. You can buy these with a gazillion different styles of chip breaker. Start out by trying one of each style before you buy a box. You will eventually find one that breaks the chip.
 








 
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