How to Knurl 1/16" hardened steel shafts??

Discussion in 'Clock Repair' started by davefr, Apr 5, 2018.

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  1. davefr

    davefr Registered User
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    Nov 29, 2008
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    Guys,
    I've been trying to come up with a process to improve the knurl on 1/16" hardened steel shafts.

    I basically want to knurl the shaft on the bottom to be similar to the one on the top in order to give it more bite into the brass gear on the right. The problem is that these .0625" O.D. shafts are polished hardened steel. A file won't even touch them. (I previously tried the method of rolling the edge of a file over them and it doesn't even make a scratch.)

    A knurl pattern would be ideal but I'd settle for anything that creates more bite.

    The shaft on the bottom is from an early Telechron rotor and the factory probably realized more bite was needed and then went to the design on the top.

    Any suggestions how to replicate this? TIA.

    P4050016.jpg
     
  2. David S

    David S Registered User
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    Wow Dave that sounds tough. Knurling has to displace metal and sound like at most it would be brittle and crack or crumble.

    Is it possible to try and locally anneal the shaft? Is it possible to close the hole in the gear to get more interference?

    David
     
  3. Uhralt

    Uhralt Registered User
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    Red Locktite?

    Uhralt
     
  4. Jay Fortner

    Jay Fortner Registered User

    Feb 5, 2011
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    Do you have room for a wheel hub? If so bore the hole in the wheel,make a hub that is wider than the wheel and stake the wheel to it. Then press that assembly onto the arbor. The wider hub will have more purchase on the arbor.
     
  5. David S

    David S Registered User
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    I like that suggestion as well Jay. Was wondering how much room he had before those holes in the gear.

    David
     
  6. davefr

    davefr Registered User
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    Thanks for all the suggestions. Yes I could close the hole in the gear to create a tighter fit and possibly supplement it with LocTite but I'd really prefer to add some mechanical bite (if possible). The hub idea is interesting but there's not much meat left in the gear wheel before I get close to it's four holes.

    I was hoping there was something like a miniature knurl designed for small hardened shafts. I might experiment with trying to anneal the shafts so a file might work.

    I already tried using a course diamond file to create a rough area for the gear wheel but the results weren't too promising.
     
  7. David S

    David S Registered User
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    Dave I think that you have to move metal around in order to accomplish your goal. The valleys in the linear knurl push up the metal to the peaks as you know.

    It seems to me like local annealing is the option if you can pull it off.

    David
     
  8. Jay Fortner

    Jay Fortner Registered User

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    If you can open the hole in the wheel .080"(2mm) that would leave enough meat on the small part of the hub where the wheel sits. May even get by with .060"(1.5mm).

    You're not gonna find a knurl that will work if the steel is that hard. I've got a miniature knurl that I made using the striker wheel from a cigarette lighter which is carbide and I doubt it would even scratch it.

    Your diamond file will cut it but it will only remove metal and you don't want to do that.
     
  9. MartinM

    MartinM Registered User

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    Maybe something like a jeweler's welder to build up an area of softer metal that could be faced-off and knurled?
     
  10. bangster

    bangster Moderator
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    Anneal, knurl, harden?
     
  11. gmorse

    gmorse Registered User
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    Hi Dave,

    Have you thought of applying one of the heat-resistant pastes to the areas you want to protect, leaving just the minimum area to be annealed?

    Regards,

    Graham
     

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