Is HSS for pivots a good idea?

Discussion in 'Clock Construction' started by dandydude, Oct 31, 2019.

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  1. dandydude

    dandydude Registered User

    Nov 30, 2014
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    Hello everyone,

    I was considering using HSS (cobalt) for palet Arbor pivots to go with jewel plain bearings? Has anyone done this before? Its easy to find because, I can cut it off a drill bit of the Dia I need. Just need to taper the end to a point. Isn't this better than hardening steel?

    Any response appreciated...

    Thanks
    Dandy
     
  2. John MacArthur

    John MacArthur Registered User
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    Feb 13, 2007
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    Dandy - I think you'd want to experiment a little. In my experience, the shank end of a drill bit is softer than the cutting end, as anyone who has ever had a bit grab and spin in the chuck knows. You can get drill stock or pin gages which probably are hard throughout the length. These might work for grinding to a point, or even shaping a pivot and polishing with a pivot polisher. Good luck,
    Johnny
     
  3. dandydude

    dandydude Registered User

    Nov 30, 2014
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    Dear John... Thank you for your reply. The drill bit I am using is not coated... It is a cobalt hss (M42) bit. Would that still have a difference in along the length?

    Thanks
    Dandy
     
  4. John MacArthur

    John MacArthur Registered User
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    Dandy - that would be easy to check with a file.
    Johnny
     
  5. measuretwice

    measuretwice Registered User

    Jul 28, 2019
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    #5 measuretwice, Dec 3, 2019
    Last edited: Dec 3, 2019
    John is right about the chucking end of drills. Drills are not suppose to be hardened, they wouldn't work very well in a chuck if they were. Think of what a no-no it is to hold an endmill in a drill chuck, that's because its hardened and the chuck's gripping power depends on the jaws getting a bit of a bite in soft material. If the end was hardened it would slip in the chuck

    As for HSS is being better, I'd say no. There is nothing about HSS that makes it harder or better wearing than correctly heat treated tool steel....except it holds its temper at much high temperatures. This is crucial on a quickly revolving cutting edge, but hopefully a not a factor in a clock. :) Heat treating HSS is about impossible without being able to hold very exact temps whereas tool steel is forgiving and easily heat treated and tempered with a propane torch
     

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