What Happened to My Part?

ddickey said:
Thanks Epanzella.
What does the partial parting do?
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The partial parting locates one end of the part (closest to the chuck) Then you measure from that groove to the other end of the part to get your .length. Leave it a bit long and then face it down to .375 from the groove to the end of the part. Go back and finish the parting and you're done.
 
If the parallel tolerance is critical as is denoted by this symbol on a drawing, in this case it does not indicate inches or millimeters..03MM is .0011xxx inches.

Holding this parallelism in a 3 jaw chuck will be tough sledding, pocketing soft jaws will help, if this is not an option part off and grind as a second operation.
Exactly what sort of accuracy are you looking for?
 
Began a similar job today, 3.130" OD X .500 thick +- .003.
40 parts in 304 SS made from 3 1/4" saw cut round stock .6" long. Bored a pocket in soft jaws .125" deep X 3.25" Dia., faced and turned one half, flipped and turned the other half.

So far the first 10 parts were <.001" out in thickness and parallelism and I was mildly surprised that turning the OD from both ends left no visible artifact, this I suspect will not last however.

This is the best option if you have to do this again in the future. If I were to remove the jaws then use them again 2 months from now I would skim cut them in place again, soft jaws are cheap.

 
Soft jaws huh? I'll have to check those out.
 
I use a set of soft jaws as well. I have 2, 3, and 4" diameters cut into the face. I still get a bit of thickness error as the jaws were not loaded when they were cut.
Pierre
 
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