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Typical Surface Finish of Twist Drill Bit

  1. Sep 10, 2011 #1
    Dear All,

    I am looking for the typical surface finish (surface roughness) of a 5 mm hole made by a twist drill bit.


  2. jcsd
  3. Sep 10, 2011 #2


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    It could be anything, depending on the material you are drilling, the drill speed, the depth of the hole or thickness of the material, etc, etc.
  4. Sep 10, 2011 #3
    Thank you AlephZero. It is stainless steel. The hole is a through hole, 5 mm diameter and 10.1 cm for the whole thing. Therefore you can say the depth is 10.1 cm? Since the length/depth of the hole is the length of the stainless steel block.

    Drill speed unknown. I would have to just give a general assumption.

    The hole is drilled by a technician in my lab. I just want to know more or less the surface roughness of the hole so that I can calculate the friction loss of water flowing through it.

    Thank you very much again!
  5. Sep 10, 2011 #4
  6. Sep 14, 2011 #5


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    Unless your Tech knows about using a drill specifically made for machining stainless and the speeds and feeds required, I would assume the upper end of the estimates for surface roughness.

    If you wish to reduce roughness then specify drilled and reamed.

    The next step in roughness reduction is honed, for more reduction then polished.
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