Quote:
Originally Posted by InFlight
There seems to be a misconception of the accuracy that can be achieved on an average small or mid-size lathe with a 3 Jaw Chuck.
Most three jaw chucks have some run out, not holding the work perfectly centered. You can measure this run out easily enough, and it will be much larger than 0.0005 on almost all lathes. This is not much of an issue if you don't move the work, and use a cut-off. As soon as you move the work in the jaws, or use some of the chucked length you will introduce inaccuracy.
Extreme accuracy requires use of a collet work holder, well-adjusted gibs, a very stiff tool post, and quite accurate measuring tools.
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Runout != diameter tolerances. Although getting concentricity with a round face is affected by the runout, the bearing press fit diameter is not affected.
The freshly rebored taig jaws had around 0.0003" of runout, and have probably increased to beyond that since I last redid them.