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What is this weird reamer? Answered

So I found this in the shop the other day. It looks like a normal reamer but it's not round. Four flutes extend to a larger diameter while four extend to a shorter diameter. The shorter flutes are sharpened just like the outer ones so they were clearly designed to cut something, even though they appear to have no clearance with which to do so. The tool has a keyed taper meaning it was intended for use in a heavy machine. The dimple in the tip of the tool does not go through the tool body. 

Can anyone identify this weird tool? None of the professors or machinists I have shown it to have any idea what it is. 


I can only make out a few of the letters stamped on the reamer .. can you post what the full inscription is please

I don't think so because the tool is straight and none of the rotary broaches have a machine taper that I've seen. That's a really neat process!

With a design like this it must be for a special job.
Take a piece of soft wood like pine, drill a suitable hole size to fit the toll just in.
Let it spin and go down - I would almost bet money on the fact that you won't get a round round hole.

We didn't drill a hole with it but I did check the geometry more closely on an optical comparator and the whole thing is straight and coaxial, all the cutting flutes are symmetrical. As far as I can tell there's no way this could do anything beyond ream a straight hole.

Maybe it has been ground such that only 4 edges cut. Less torque, more clearance for chips.

is it possible that an ordinary reamer was ground incorrectly

We considered that but the error would have to have been so large that the tool would be scrapped, and left unfinished. This tool is finished and was shipped to our shop at some point, so it must have some function.