Is there a way to cut down a disc diameter from the face?

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lslarry86

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I have a 4 inch diameter disc, 3/8 inch thick aluminum, with a particular hole pattern. I need that same hole pattern in a 3 inch disc. I have already cut one down from the side, 5 thousandths at a time, on my Jet lathe. It took close to an hour and made a pile of shavings.

Is there a way to cut into the face of the part to set the new diameter, and end up with a ring as waste instead of a pile of oily shavings? I tried turning my tool rest 90 degrees and pushing a parting tool into the face, but it wandered, and started making a lot of noise after the first 0.1 inch or so.

Is there a different tool designed for this operation? Some kind of diamond point?
 
As already mentioned, Trepanning. You are close to the right idea with parting from the face. The problem is you need a tool that fits into the circular cut. You pretty much need to grind that yourself to match the cut diameter.
 
Another method is to turn the OD only by pushing the plate against the chuck jaws with the tailstock center, this if you can tolerate a center drilled hole, cuts can be tolerably large, just so the plate does not slip against the jaws.
A parting tool will not work well on a face, it does not have enough side clearance on the OD side of the cut.
 
I think if it took an hour to remove 1/2 inch from the OD of 3/8 thick aluminum you are doing something wrong with your lathe, cutting tip geometry or perhaps RPM would be my guess. I would think it should only take a couple of minutes and would be faster than trepanning.
 
I think trepanning can be dangerous if you are new at doing it. So be AWARE !
It’s easy to break the tool and have parts fly all over.
I used to do production runs of trepanned tools . Thousands of parts.

jimsehr
 
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