Boring aluminum getting messy on lathe

[SRT Mike]

Originally Posted by erd39030 60 Hp? That's a lot of machine for little .100 DOC on aluminum!

better too big than too little

[SRT Mike]

Originally Posted by Geof Can't help you on the capability of an Okuma. And I am tempted to report you to the Orangutan Antidefamation League . Do you have a description for G74? I can screen capture a page from the Haas manual that describes it if you like.

Thank Geof, I was able to find a description online.

Ironically the Okuma manual has at least 20 pages devoted to tool radius compensation, and a single half-page on the entire G74. It lists the parameters and says things like "I - the amount to step with each move". Gee very helpful

But with the online help I should be able to nail it down. Thanks!

[riverrat]

hmmmmm.
so me's an orangutan?
we be havin a league?
who we be playin?
da raiders?

da riverrat

[SRT Mike]

I bumped up the feed to .010 IPR, 2500RPM on the boring - MUCH less stringing of chips but still some. Pushed it up to 0.012IPR and I got no stringing, but it was sort of singing (a high pitched screeching noise). I'll mess with it a bit more, see if I can get it any better but if what I got now is what I have to live with, it will be OK.

Cycle time was also waaaaaay faster (thanks on that front!) and I turned the original OD with a .015 stepover on the OD roughing with the CNMG 432 AL bit, finish is actually pretty damn good. It's getting turned on a 2nd op anyway so no biggie..

Thanks for the help

[Paul_S]

If you're interested, you can calculate your finish for your finish pass. .0567 x sqr(tool radius) x sqr(AA finish wanted / 125) = ipr for finish. If you want an RMS finish use .0542 instead of .0567.

[g-codeguy]

Originally Posted by SRT Mike I bumped up the feed to .010 IPR, 2500RPM on the boring - MUCH less stringing of chips but still some. Pushed it up to 0.012IPR and I got no stringing, but it was sort of singing (a high pitched screeching noise). I'll mess with it a bit more, see if I can get it any better but if what I got now is what I have to live with, it will be OK. Cycle time was also waaaaaay faster (thanks on that front!) and I turned the original OD with a .015 stepover on the OD roughing with the CNMG 432 AL bit, finish is actually pretty damn good. It's getting turned on a 2nd op anyway so no biggie.. Thanks for the help

That screeching noise is called chatter. Not good for carbide inserts. So what if you need the 1/2 inch bar for another job. It isn't that hard to reset the geometry for it. Good thing you are running aluminum. That small insert couldn't take anywhere near that DOC or speed and feed in a harder material without breaking and wiping out the tool. Do yourself a favor, and stick a 3/4 inch boring bar in the machine.

How much material is coming off the OD? .015 stepover is ridiculously light for roughing. Any catalog I ever read said to bury the insert at least 1/2 the tool nose radius of the insert for finishing. I don't follow that rule. Normally I leave .005 or .01 DOC for finishing, even on aluminum, but it does cause stringing. However, since this part gets finish turned in another operation, there is no need for such a light DOC or slow feedrate for the finishing pass. Normally I am holding tight tolerances and a good finish, and these practices are a carry over from running other materials. Aluminum jobs are few around the shop I work in.

I think someone mentioned using a G96 instead of a G97. Don't bother at those diameters. Run the machine as fast as you feel it can safely run with that size chuck.

BTW, I agree with you about the Okuma manuals. Not very "friendly". Hardinge manuals are MUCH better.