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WW / 8mm collets and edge finding

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  • WW / 8mm collets and edge finding

    I typically reserve the use of my 8mm collets for grinding operations. I have an accessory spindle that mounts on my lathe's QCTP. I was working on a piece yesterday that required a single chucking and indexed features in both axis (the end face and the OD). I centered my 8mm spindle to the lathe spindle with an indicator mounted in the latter. During set-up, a thought hit me which I had never considered before... There's no real "edge-finders" that can work in an 8mm spindle. Technically, I guess, you could mount a 1/4" shank edge finder with a .200 tip, but it would extend relatively very far out from the spindle. In this case, my spindle is integral to my QCTP holder. It does not fit in a bore, so it cannot be replaced with a microscope or other optical device to find position.

    So how do you find position with a typical WW collet spindle on a watchmakers' lathe?! My experience left me wondering this question.

    I have a second milling spindle that accepts a larger collet that also fits the same lathe I was working on. I am used to using it with a normal, 3/8" shank, edgefinder. In this specific instance, though, it was much easier to mount the smaller 8mm spindle. Hence the unusual situation (for me). Just curious, really. Are there physical methods that are common? For example, chucking a bent shaft in the spindle and comparing to the work as you rotate position? Or something along that line? What kind of accuracy might be expected from such a method? It just struck me as odd because watchwork is so precise, yet I was lost on how to find position without an edgefinder in this case. Thanks in advance for your thoughts!

    [EDIT:] As a simple curiosity---it isn't really integral to the question---here is the part I was making sitting atop its broken original:
    Last edited by Arthur.Marks; 03-20-2012, 03:04 PM.