Need Help!- 6061 Interupted Lathe Cut

[Billet Sean]

Need some tooling advice. We're getting ready to set-up some 6061 aluminum. It's 3" O.D. with an interupted cut.
Here's a picture of the finished part:
http://www.bmikarts.com/shop/?shop=1...showFullImage=
What I need is some advice on inserts. We use to buy 3" dia. solid material, but realized that we can save about $.50 in material per hub and labor on top of that by having an extrusion made with the clover shape. But that poses a problem when we turn it (the interupted cut). I've had problems with this kind of cut before. Usually left a cloudy finish reguardless of what speed/feed I used. And i'm not very familure with insert geometry. We have holders for CNMG, VNMG, and WNMG inserts. Can anyone recommend a insert for this job? Also, we're getting 2500lbs of aluminum for this job, that'll be about 2700 of these hubs. So tool life is an issue. Finish is very important. Functionaly it doesn't make a bit of difference, but the market these are sold in it makes all the difference. Thanks, Sean

[mc-motorsports]

There is no picture at the link above, but I can picture a go-cart hub. I would use a CNMG as the VNMG would tend to chip out faster. Use more RPM and ligher cuts, and yea, the finish is always a little diffrent than a consant cut.

[fizzissist]

The inserts you mention are all negative rake, which are good for interrupted cuts, but you'll get nicer finishes in al with positive geometry.

One trick I have had pretty good success with, though more often necessary because of my unique chip control issues, is doing an a second finishing pass. I'll change the offset for the second pass and take off only .0005". I've been lucky so far, and seldom get smearing unless the tool is really tired.

When you say "cloudy", is that like in, smeared? Right after the leading edge of the interruption?

Have you tried something like the Sandvik Wiper WNMG?

One thing you might consider is electropolishing..hides a multitude of sins, the parts come out really shiney (including the sins that didn't get hid), and it's not that expensive.