What is the drill bit on the far left hand side of the machine in the first picture?

I believe it cuts holes shaped liked those in the second picture, which is something I'm trying to achieve. Is it a large countersink bit? I think the hole is about 24mm wide.

1 Answer 1


That is a countersink. I would not call it a drill bit, as it's intended to open and shape a hole. Typically a through-hole of the smallest diameter is drilled, then the countersink is performed as a secondary operation. It is typically not advisable to try and "drill" a hole with a countersink.

  • That's a pretty big countersink. What's the difference from those and chamfer bits? Technically I think, those are chamfered holes, as they are not intended for fasteners.
    – Mazura
    Commented Jun 23, 2017 at 15:46
  • @Mazura IME, Chamfer bits have long longitudinal flutes, almost like a tapered reamer. Countersink bits have a different cutting head that is usually a single round flute. Functionally there is not a ton of difference. Commented Jun 23, 2017 at 16:00

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