I inherited a load of tools from my father. Among them was this bit. I have never seen one like it, and don't know its purpose. It has six straight splines set at an angle to the long axis of the bit and sharpened to act as cutters. The diameter at the splines is 1/2" and at the smooth shaft slightly less than that. There is a hole in the tip that is 1/8" deep. The first half or so of the hole is conical, and the deepest part is cylindrical. I do not see or feel any threads in the hole. The following is stamped into the smooth part of the shaft: "National Detroit High Speed IVF [those three letters are slightly obscured from wear, but I think that's what they are] 1/2 [which must be the diameter]." It will cut into the edge of a piece of wood if put in a drill press with the wood pressed against the rotating bit, but the cutting is slow.

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2 Answers 2


That is a straight reamer it's used to make a hole a precise size (drill slightly under-sized, ream to size, more precise than simply drilling to size.) The hole at the tip is used in making it and/or sharpening it (as made it will be exactly 1/2" - after re-sharpening it will be slightly less than 1/2")

It is NOT a router bit (and putting side loads on a drill press can have unfortunate consequences, so I suggest not trying to use it that way anymore)

  • aka "chucking reamer" Mar 8, 2021 at 3:46
  • 1
    It is NOT a router bit How can you tell? I've seen router bits which look very similar. I'm not doubting you, I'm just thinking this answer will be more useful for others if you can outline the specifics of what made you confident in your determination.
    – R.M.
    Mar 8, 2021 at 14:05

Adding to Ecnerwal's answer, it's a 'straight-shank straight-flute' reamer, for making very accurate diameter (parallel sided) holes - but not in wood. It's for metal. Drill the original hole 10 - 15 thou (0.010 - 0.015") smaller than the finish, then ream to an accurate hole.

Being part of a machinists equipment, reamers are often not good to fit into a drill chuck, as they will have a Morse taper instead, which is designed to fit into higher end pedestal drills. This one doesn't have the Morse taper.

  • 3
    Additionally - never turn them backward, always turn them forward, use cutting oil, and they're only good for removing ~10-20 thousandths of an inch. They're not drill bits.
    – Criggie
    Mar 7, 2021 at 1:13
  • 3
    That's a lathe one
    – Trish
    Mar 7, 2021 at 15:52
  • 1
    Plenty of machine tools are like OPs - it's meant to go into a collett, just the same - not into a drill chuck.
    – J...
    Mar 8, 2021 at 13:19
  • I am a woodworker, not a machinist. Can you tell me what an OP is? Also, why does this reamer go into a collet and not a drill chuck? Mar 13, 2021 at 21:48

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