I need to cut 1 inch wide by 5-inch length pockets into various types of hardwood to a depth of 1.5in.

My question is how do I pick the cutting diameter of the spiral bit. I understand that probably just about any diameter could be used but I'm looking to minimize my machine time.

  • Are these rectangular pockets? If so, what radius corners can you tolerate? If you want exact corners you will have to cut these by hand, and the machining time saving by going much beyond 6mm/¼" will be completely lost by the extra time to cut the corners. Jan 28, 2019 at 12:26
  • They are rounded. No exact radius is needed and so the radius will be determined by the bit cutting diameter.
    – Vindictive
    Jan 29, 2019 at 1:15

1 Answer 1


I don't think it makes much difference. If you have a smaller cutter you can move the cutter faster; if you have a larger cutter you will have to move it slower. The limiting factor is how fast the motor can cut wood.

Obviously if you use an extremely thin cutter your CNC machine won't be able to move fast enough, and if you use an extremely large cutter it will have difficulty accurately controlling the speed low enough, but over a broad range of cutter sizes it shouldn't much matter.

See also this question which also about efficiently removing wood with a router.

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