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  1. #1
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    Default Hercus model ARM lead screw spinning too fast.

    Hi All,

    I'm just a hobbyist enjoying my old Hercus model A. I have made all sorts of bits and pieces for my motorcycles, including cutting imperial threads.

    My son has a Hercus model ARM and with the gearbox set to the slowest lead screw setting, the lead screw is spinning too fast.

    We tried to cut a thread the other day with a 1mm pitch and using the correct positions on the two gear box selectors and with the chuck driven by the back gears, the thread ended up with a pitch of a little over 5mm.

    We seem to have some incorrect gears? Any help would be appreciated.

  2. #2
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    Jun 2007
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    sydney ( st marys )
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    Default

    What gears have you got set on the stud banjo and screw at present?
    What spare gears do you have?

  3. #3
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    Default

    Quote Originally Posted by pipeclay View Post
    What gears have you got set on the stud banjo and screw at present?
    What spare gears do you have?
    Thanks for responding pipeclay.

    The stud gear has a 24 running on the tumbler gears and a 45 outside that running on the idler gear which is then running on a 20 on the banjo? with a spare 50 outside that.

    Sorry - not sure which is the banjo gear and which is the screw gear.

  4. #4
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    Default

    Hello again pipeclay.

    Your response has prompted me to find the solution I think.

    The 45 should be down on the banjo? running on the idler gear.

    The 20 should be on the stud gear.

    The 50 is the spare stud gear and should be stored on the outside of the banjo.

    Does that sound correct?

    I have let my son know and he is going to try that.

    Thanks again for your help.

  5. #5
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    Default

    The thread chart on the box will show the correct position for the gears depending on fine or coarse thread.

    The gear on the outside of the reverse tumblers is the Stud the gear on the Banjo bracket is the Idler and the gear on the outside ( left of gearbox from standing in front facing headstock ) is the Screw.

    On the Screw there should be 2 gears or a gear and spacer, this takes up the additional shafting on the screw shaft.

  6. #6
    Join Date
    Aug 2015
    Location
    Adelaide
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    239

    Default

    Quote Originally Posted by pip-pop View Post
    Hello again pipeclay.

    Your response has prompted me to find the solution I think.

    The 45 should be down on the banjo? running on the idler gear.

    The 20 should be on the stud gear.

    The 50 is the spare stud gear and should be stored on the outside of the banjo.

    Does that sound correct?

    I have let my son know and he is going to try that.

    Thanks again for your help.
    What you have there is correct, unfortunately Hercus did not put the screw gear teeth number on the gearbox plate on the 9" models yet on the 260 they did.

    here is a link to the standard gear configurations for the lathe models.

    Standard gear configuration for Hercus 9" and 260 lathes

  7. #7
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    Default Thanks Everyone.

    Quote Originally Posted by Tinkerer77 View Post
    What you have there is correct, unfortunately Hercus did not put the screw gear teeth number on the gearbox plate on the 9" models yet on the 260 they did.

    here is a link to the standard gear configurations for the lathe models.

    Standard gear configuration for Hercus 9" and 260 lathes
    Thanks heaps tinkerer77 and pipeclay- my sons Hercus model ARM is functioning correctly now and as a bonus, you have directed me to information that will allow me to cut a metric thread on a flywheel puller for my old Montesa Cota 348 using my imperial model A.

    I'm loving this forum.

  8. #8
    Join Date
    Aug 2015
    Location
    Adelaide
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    Default

    There's plenty of people on the forum that are always willing to help out, it's all a bit confusing when you are starting out, not sure if you found this but I put this together a little while back to help explain compound gears

    https://metalworkforums.com/f189/t20...9-model-lathes

  9. #9
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    Oct 2021
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    Default Thanks again.

    Quote Originally Posted by Tinkerer77 View Post
    There's plenty of people on the forum that are always willing to help out, it's all a bit confusing when you are starting out, not sure if you found this but I put this together a little while back to help explain compound gears

    https://metalworkforums.com/f189/t20...9-model-lathes
    That's really useful Tinkerer77 - Thanks very much.

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