Quote:
Originally Posted by InFlight
If you measured the current runout of your own lathe you might be surprised. Most will be over the 0.006 value which was my point.
If your drilled off center; your applying a bending load into the resolver shaft every rotation with direct mounting. At 100 rpm your going to be challenging a floating mount, and getting higher loads in the resolver bearings.
This is the reason many of us prefer alternate non-direct mounting. For close mounting a no contact magnetic rotation sensor would make far more sense.
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We have two lathes, one that is so terrible it cannot make straight cuts of any depth (and I mean
any depth) and another smaller one that belongs to a teacher. The teacher one was just bought this year and has runout of well under 0.001" with the stock 3-jaw, which I bored out slightly for accuracy. The larger one, for all it's junk, has only .003" TIR on the 3-jaw. I've gotten the tailstock inline with it once before to within 0.001", but the machine didn't hold up very well over time. I've never experienced a failure with plastic encoder mounts regardless of mounting, just because they are so flexible. I'm all for magnetic encoders, but as far as the COTS options go they are pricey compared to AMTs or similar.
If
our lathe can do it, any lathe can do it.
Seriously though, getting stuff within 0.006" is not difficult if you check it every once in a while. Grinding the chuck jaws and using a good indicator help immensely.