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Which angle on spotting drill?

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  • Which angle on spotting drill?

    Hello again:

    Another question from me today. Can you tell I'm about ready to place an order?

    Anyways, I've got the usual centre drills but I'd like to try some spotting drills. In the catalogues they show spotting drills as having 90 deg. or 118 deg. angles. I'll mostly be using these on my 7x12 minilathe, so which angle would be the one for me to get? Why the difference? Thanks again in advance for all the help you folks give.

    John

  • #2
    Well, since a spotting drill is used for starting holes to be drilled and most drill bits are 118آ° I would buy the 118آ° type.
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    • #3
      I'd go for the 90 degree. They work fine with 118 & 135 degree drill points.

      Plus, used in a drill press or mill they make a "standard" 90 degree chamfer or countersink on drilled holes.

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      • #4
        yeah i like the 90 degree points for the reason listed above... puts a perfect 45 chamfer on your hole.

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        • #5
          All of the above, buy both they are cheap and last forever. I have both angles in 3/8, 1/4, and 1/8. I like the 118deg for starting my holes that I am gonna drill. And the 1/8 90deg makes a great engraving tool.

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          • #6
            The 90 deg points are easy to figure depth needed to get desired chamfer diameter. half of diameter is depth, no trig, no calculator.
            And you get 45 deg chamfer.
            Russ

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            • #7
              90 degrees is a good spotting angle, for this angle wanders less. No matter the length of the drill, there is a chance of wandering from dill flex, holder flex, had flex, table movement.......

              A 90 degree point has less "chisel point" (the area of the drill that starts the cut, and tends to "set off" the drill due to not cutting but "moving metal" like a chisel) from my observations, and gets to the cuting edge faster.

              The chamfering reasons are also very good to think of.
              CCBW, MAH

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              • #8
                Thanks guys. Great replies. You gave me some good info that I was not aware of. This board is a great source of knowledge. Thanks again.

                John

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                • #9
                  For the most accurate results always spot with the same angle you will be drilling with. I doubt that you will be drilling with a 90آ° drill. With any other angle the point or the corners will hit first. Keep in mind that the only reason you are spoting the hole is to accurately start your drill.

                  Steve

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