The Shop > Tools
Another Inverted parting tool ?
Pelallito:
Hello,
I have an inverted parting tool holder for the Aloris that works from the back. You feed it in with the chuck spinning in its normal direction.
I have never really had a lot of luck using it. :bang: It digs in and then raised up over the cut. I have tried many combinations of things and it never cuts well for me. I am using it on a 12" Atlas and am wondering if the lathe is too light weight for this tool. Perhaps I don't have my gibbs set up tight enough? I have the factory gibbs that are made from some sort of plastic. Should I replace them with steel or something else? Would that make my machine a little more rigid?
Thanks for the help.
Fred
Bernd:
--- Quote from: Pelallito on March 26, 2009, 07:11:45 AM ---Perhaps I don't have my gibbs set up tight enough?
Thanks for the help.
Fred
--- End quote ---
Fred,
I have that trouble on my 9 X 19 Grizzly bench lathe. I noticed it was picking up the back of the slide.
I don't know what the remedy would be. Maybe Bogs (John) will make a comment here as to how you can fix that. He's pretty knowledgeable on that. Bogs?
Bernd
Pelallito:
Bernd,
Thanks for chiming in on this. I hope that Bogs does get involved. For one thing, besides being very knowledgeable, he had an Atlas that he used for many years.
I bought that particular holder because I had read that it would be better for a light lathe. :scratch:
Fred
bogstandard:
Hi Fred,
I'm here and reading, but don't hold out much hope of helping.
So what you are saying, this holder fits onto your QCTP, with the tooling upside down, sticking out to the rear rather than the front, and is then is fed from the rear of the chucked piece.
If that is how it is done, the mechanics are all wrong.
As long as you are using a QCTP there will be no advantage whether cutting from the front or rear. A QCTP will never be as rigid as a tool bolted straight down onto the cross slide. That is why people make the solid toolholders to bolt straight down onto the cross slide to do rear tool parting. That to me is where the advantage comes from to make the cutting easier.
Bernd also made a comment that might have some bearing on the subject.
--- Quote ---I noticed it was picking up the back of the slide.
--- End quote ---
On a normal setup you are using the toolpost on an area of the cross slide that has full support of the gibs. Most lathes are the same, and not designed to have the toolpost working on the very rear of the machine, because the dovetails don't reach that far back. So you might be operating in an area where the the underside dovetails aren't supporting the cross slide as much. It is easy to check, put the toolpost in the area you are working in, and feel under the cross slide to check whether you have full length support of the gibs.
Because I don't have any problems with parting off, I have never had to resort to drastic measures, and of course I can only give you maybe cures for your problem.
If none of the above solutions look to be the cause, then maybe you should look at how I get uneventful parting off.
I always set my tooling a few thou high. This allows for the slight downwards flex of the tooling, so when it is at it's maximum 'bend' the tooltip ends up at the right height for cutting. It takes a little to find the 'sweet' spot, but once it is done, no further action is needed.
I would try setting your tool about 5 thou low (opposite to mine), and try a cut, if it still tries to lift over the top, try it a bit lower. If it doesn't want to cut, reduce it to a couple of thou and try again. You will eventually find the spot of maximum bend, and it should then cut thru like a hot knife thru butter.
I do hope these suggestions help you with your problem.
John
Pelallito:
John,
Thanks for your advice. I was afraid of what you pointed out. I will try what you recommended, though. Perhaps I should get these for the Atlas-
http://www.statecollegecentral.com/metallathe/A-11.html and
http://www.statecollegecentral.com/metallathe/MLA-6.html and
This one is new to me
http://www.statecollegecentral.com/metallathe/MLA16D.html
I liked that one too!
Thanks again,
Regards,
Fred
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