nick952
Member
- Messages
- 261
- Location
- Wrexham, N.Wales
If I turn the OD, turn the part round and turn the rest, I can see a line where the two cuts meet, but the gauge doesn't move. I thought if a piece is within 1/10000th that I would not be able to see it?
When the O.D. is turned, you are in fact producing a very fine shallow thread and so a very fine helix angle in the surface finish. When you stop the feed at the end of a cut, you lose this helix and produce a circular burnished ring.
After you turn the part around in the chuck and finish turn the O.D. you again produce a helix angle, but this is now opposite to that on the first turned dia and will not remove the burnished "ring". In fact, because of the crossed helix angles, you would see a faint diamond knurl type pattern under high magnification (if you trverse past the circular burnished ring on the second operation).
If the needle on the DTI is still moving, then there is still some movement in the setup, even if you've stopped moving the slide. Remember the DTI magnifies any movement that you could not see with the naked eye, up to a level that you can and 1/10000" aint a lot of movement.
Nick.
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