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  1. #1
    Join Date
    Dec 2021
    Location
    NZ / Aus
    Posts
    2

    Default Clarification on Missing Gear - Required or not for cutting threads

    Hi All,

    New to the forum and the Hercus lathe... Mine is an Imperial Model A

    Firstly Thanks to some smart people for other posts around cutting etc that have made things easier to understand but i am still slightly confused so figured i would ask and get clarification.

    I am missing a tumbler gear (which easy fix) and know i require some new stud gears to cut metric (40,48,28 - https://metalworkforums.com/f189/t20...9-model-lathes).

    My confusion is around that the idler has been setup with a 63 tooth gear (which from what i read can be used instead of the 100/127 gear for metric threads - but only seen setup instructions for 100/127) So i have no idea how it is meant to be setup and/or am i missing a gear to use that function & cut imperial threads as i see machines with "change gears" before the idler gear

    Clarifiy the gears i have - 20,40 stud 80-63 idler and think its 56 screw (others i will sort out once i know the go)

    See attached picture..

    IMG20211226225833.jpg

    Thanks for any help or a point in the right direction as this is going to be a life saver for my equipment when it can do its thing...I will be installing a DRO / Motor upgrade and possibly quick change tool post if and when it earns its keep or one of the boys toys sells.

  2. #2
    Join Date
    Jan 2004
    Location
    Mackay North Qld
    Posts
    6,446

    Default

    Hi NZ - OldStuff

    Welcome to the MetalWork forums.

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    ou will find plenty here who have the same interests as yourself.

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    Again, welcome to our forums.

    Grahame

  3. #3
    Join Date
    Aug 2015
    Location
    Adelaide
    Posts
    239

    Default

    Hi mate

    The gears you have are right for the lathe except for the weird compound gear, not sure why there's a 63 tooth attached to the 80 tooth gear, as you said the 100/127 is standard for the metric but you can use this set as well https://australianmetalworkinghobbyi...et-500x500.jpg

    Good luck and happy turning

    Cheers Steve

  4. #4
    Join Date
    Oct 2008
    Location
    Cairns, Q
    Posts
    666

    Default

    Quote Originally Posted by Tinkerer77 View Post
    Hi mate

    The gears you have are right for the lathe except for the weird compound gear, not sure why there's a 63 tooth attached to the 80 tooth gear, as you said the 100/127
    Steve,

    100/127 = 0.78740...
    63/80 = 0.78750, a very close approximation, often used to replace a 100/127 compound gear if the 100/127 compound gear is too big to fit in the available space.

    If space does not even allow the 63/80 compound gear, a 37/47 compound gear = 0.78723... is also close enough for most practical purposes.

    Frank.

  5. #5
    Join Date
    Aug 2015
    Location
    Adelaide
    Posts
    239

    Default

    Quote Originally Posted by franco View Post
    Steve,

    100/127 = 0.78740...
    63/80 = 0.78750, a very close approximation, often used to replace a 100/127 compound gear if the 100/127 compound gear is too big to fit in the available space.

    If space does not even allow the 63/80 compound gear, a 37/47 compound gear = 0.78723... is also close enough for most practical purposes.

    Frank.
    Thanks Frank

    I read about the 37/47 compound arrangement but I wasn't sure about the 80/63, but after you mentioned it I do remember seeing a spreadsheet a guy did a long time ago with the different compounds and stud and screw gears, I know there are different ways of getting the same result with marginal error over a fair distance, Hercus had a 135/127 compound for cutting imperial threads on metric b and c models and I thought the 127 tooth was a big gear on the back.

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