Was just gifted what at first glance I thought was a 2" flattening bit for a 1/2" shank router.

But it has a spur and cutting rim like a forstner bit except there's no way with a shank of its proportions it could be a forstner bit. The spur is proud of the rest of the chopper and cutting rim and probably sharp enough to cut a groove.

It had a non-descript marking "CPT 44160" that google did not offer any clarity on. I'm totally at a loss for what this cutter head is for. It's gorgeously machined and despite being quite old is still super sharp.

Any help you fine folks can offer here is much appreciated.

Is this just a weirdly specific router bit designed to cut a 2" groove with a tiny v-groove in the middle? Is it not a router bit?

This is a picture of the bit.

  • 1
    If this is what I think it is they go by a range of names, including the less-useful end mill, but effectively it's a drill bit. Think of it as basically a fancy and hard-wearing version of a Forstner bit. Some are exclusively made to bore the holes for "Euro-style" hinges.
    – Graphus
    Jan 7 at 9:52

2 Answers 2


Not a router bit… it’s used to cut cups when used in a drill press. One technical description would be ‘hinge boring bit’. (You’ll see a lot like it in the 35mm size.)

  • That makes sense for why the shank l the bit is so shallow. Dont need to make deep cuts when you're just installing a hinge into a cabinet carcass. Thanks!
    – YoStephen
    Jan 15 at 6:27

What you have there is known as a Forstner bit. They're used for drilling large, relatively clean holes in wood. They're designed to cut in the axial direction and shouldn't be subjected to transverse loads as in a router. If you're drilling a thru-hole with one you can get better results by using a backing board as they tend to blow out the back side when they break through. Alternatively, you can drill almost all of the way through one side so just the point sticks out, then flip the piece over and finish drilling from the other side.

  • 1
    This isn't actually a Forstner bit. The key design features of a Forstner bit were as laid down in Forstner's patent. There are many lookalike bits, including wave bits and sawtooth bits, that are sometimes generically referred to as Forstners today but only those with a continuous rim are true Forstners. A rim of any kind is conspicuously absent from the bit pictured.
    – Graphus
    Jan 15 at 7:56

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