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35321Re: [MILL_DRILL] how to drill deep holes

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  • Jerome Kimberlin
    Feb 2, 2014
      On 2/2/2014 8:35 AM, mayo3013@... wrote:

      I think the key to is with "Deep holes" is not what we do when we pass 3 X dia. But what we do before. Like was stated start with a center drill move to a screw drill, then a jobber, and then the long bit. Now that said I do not own screw lengh bits. I do remember having to drill some small like 1/8  hole and ordering long bits. I did start with certer drill and the a jobber chucked up to the flutes and finished with the long bit. Ihad to peck gently though because the bits really want to flex. BTW it was 3/8 brass 2-1/2 or 3" long.

      A center drill suffers from the same problems an ordinary drill has.  Start with a spotting drill and drill in as far as necessary to encompass the diameter of the regular drill you want to use.  That way, the regular drill has a very accurately placed starter pip to guide it.  Further, the spotting drill angle should be the same as the ordinary drill you use or vice versa if you grind your own drills.

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