Parting Difficulty

prasad

prasad

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I am trying to part an aluminum rod 1.5" diameter using my G4000 9x19 lathe and a 1/8" HSS parting tool. I am getting loud growling sound with heavy vibration. I have tried Re-Li-On cutting oil, WD40. They help a bit but no enough to make the parting smooth. The tool height is adjusted to center height correctly. Varying spindle speed helped a bit but not enough. Any advice?

Thanks
Prasad
 
In case the worpiece protrudes more than a few inches from the chuck it may need support from the tailstock.
 
The work piece sticks about 2 inches from the jaws and parting tool is about 1 1/4" away from the jaws. I am using 6" 4-jaw chuck.
 
I used to have trouble with chatter when parting from time to time, but since going from a 1/8" blade to a 3/32" blade the problem rarely occurs any more. Hard to believe that 1/32" in width would make as much difference as it did!
 
All guessing at this point, but it could be any one or a combination of dull tool, parting too far from the chuck and/or too much tool sticking out of tool holder. I would check all 3. And make sure saddle, cross slide and compound gibs aren't loose. Hope this helps.

Tom

Edit: Terry posted while I was typing and made a very valid point. With 3/4”+ of the parting tool sticking out of the tool holder, a wider parting tool might be the ticket.
 
All good advice. Chatter is your machine saying, "I'm not rigid!"
 
Thank you guys, I will have to buy a wider parting bit then. I tried it again with live center mounted and at one point I think the parting tool got caught. The lathe clutch acted, workpiece slipped in the chuck and became eccentric. So I stopped the parting process and used a hacksaw to cut the piece off. Not exactly to my desired method. Well I am learning.. Every thing that happens here is gained experience... Tomorrow will be better, ha ha.

Thank you everyone for sharing your knowledge, everything was useful...

Prasad
 
prasad said:
I tried it again with live center mounted and at one point I think the parting tool got caught.
Click to expand...

That's exactly what I would expect to happen. I have seen more than once when someone suggested using a tailstock center to support a long work piece for parting. I haven’t had a need to try it, so I’m working on theory here, but it sounds counter intuitive to me. Seems to me that if you have the work piece pinned at both ends, the side force from the parting tool will tend to bend the work piece into an arc, which would widen the parting groove on the backside and narrow it on the front side, pinching the parting blade. Am I wrong?

Tom
 
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