Is Polished and ground shafting straight enough for a taper attachment build
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    Default Is Polished and ground shafting straight enough for a taper attachment build

    I need a taper attachment . The ones for my lathe are cost more than what it is worth to me IF one in decent shape can be found.
    I was wondering if new polished and ground shafting is straight enough to use to make one.
    The attachment would be used to turn MT 3's .
    I have looked around for a straightness specification but not seen anything.

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    True hardened, precision shaft shows a straightness of .002 per foot, Thompson 60 precision shaft shows .001 per foot, so knowing that, I would doubt than TG&P shafting is going to be any better than that..probably worse.

    I think most precision shafting used in guide rails relies on the support rails to pull out any slight bow or bend. I sure would investigate precision shaft before I made the move to TG&P shafting.

    Stuart

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    I've seen straightness tolerances on shafts meant for linear guides, usually .001"-.01" per foot, but I've not seen a general spec for them. I would suspect the forces generated by lathe tooling would flex all but the most oversized round bar out of that tolerance pretty quickly, any instance of ground rod used for a machine tool way I've encountered has been braced and shimmed by a V or corner bedding. The few taper attachments I've used have all been box ways.

    McMaster-Carr

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    Every TGP shaft supplier will list diameter and straightness tolerances.
    Usually 0.001" - 0.002" per foot.
    If that is not straight enough for you, centerless ground rod can be found at less than 0.001" per foot

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    When I designed and built a small machine tool in 1976, I used Thomson ball bushings and 60 Case shafting. Worked great. The shafting is soft enough down the middle to drill and tap the ends. I spot annealed a place on the hard surface to drill and tap for a set screw.

    60 Case Standard Shafting | Thomson

    The round Thomson parts can make a good taper attachment, or you could go with rectangular bar and linear ball bearings. There are usually some on eBay.

    Larry

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    Taper Attachment Plans


    Sent from my iPhone using Tapatalk

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    Thanks Stuart,, thats what I was needing to know

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    That looks like a great way to build the attachment . Thank you ED

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    Thank you Larry,, I have a line on new linear bearings with blocks and was wondering if they would need to be indicated into straightness and then locked down . You answered it for me.
    Thanks ED

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    Thanks Stuart,, thats what I was needing to know

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    Thanks for your input,, this idea is getting more complicated than I figured .


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