"Terry Coombs" wrote in message
...

I just got to wondering about internal stresses in 4140 round stock . I'm
making a part for an oilless compressor , and have it roughed a bit
oversize . I know that some steels and other metals develop internal
stress from forming operations , and need a few hours to let the stresses
equalize before finishing machining so the finished part doesn't distort .
Got to wondering if 4140 is one of them .
--
Snag


It is generally accepted that all parts have stress, the result of the
manufacturing procedure, as you alluded. Hot rolled materials tend to have
much less.

Good shop practice dictates that one roughs parts, leaving sufficient
material for finish machining, with total cleanup. The less material
remaining, the better, as the piece will more closely represent the finished
object, and the small amount of material removed in the process should make
very little difference in movement of the part. I expect that unless you
have a very critical dimension, less than .0002" tolerance, you should be
fine.

Nice job. I spend a lot of my time trying to have folks understand that
roughing is a very important part of machining. Some don't pay attention
(until they have the pleasure of reviewing the resulting scrap, anyway).

Time can be a factor, but the roughing should release much of the stress.
If you have doubts, allow the part to age a day.

Harold