Pivot Drills vs Twist Drills

Discussion in 'Horological Tools' started by Dave D, Feb 14, 2018.

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  1. Dave D

    Dave D Registered User
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    Apr 5, 2006
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    Is there any difference in them? I understand that they look different, but is there any advantage/disadvantage of one over the other? I need to make a part with a hole that is .018". Is there a reason I might choose a pivot drill or a twist drill? Or, the other way around? I have both.
    Dave D
     
  2. wefalck

    wefalck Registered User

    Mar 29, 2011
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    I gather it depends on the material and the depth of the hole.

    This diameter (0.018" = 0.45 mm) should not be a particular challenge. Deep(er) holes will require more frequent clearing with a pivot-drill, as it doesn't have the helix. Pivot-drill might be better than twist-drills in soft brass, where the latter might dig-in and break. Pivot-drill are a bit stiffer than twist-drills that are typically longer and have a thinner 'core'.
     
  3. praezis

    praezis Registered User

    Feb 11, 2008
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    Main advantage of pivot drills: they are easily resharpened. Not at all easy with helical drills.
    Frank
     
  4. shimmystep

    shimmystep Registered User
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    Mar 5, 2012
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    A pivot drill will give you greater accuracy to desired diameter than a helix drill of that size, and are less likely to go off course. As said a pivot drill bit is stiffer, a helix drill can leave the hole slighter larger in diameter at the entry end.
    Pivot drills will require more cleaning of swarf as you go, and they need like a good starting centre dot/hole.
    A hole of the size you need, just personally speaking, I use a pivot drill, with a drop of cutting fluid.
     
  5. Dave D

    Dave D Registered User
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    Apr 5, 2006
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    Thank you guys for confirming what I suspected. I managed to drill the holes without a problem.
    Dave
     

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