Boring Machine Auger Bit Question

[Brian_Weekley]

I acquired a nice looking auger bit for my boring machine at a local garage sale.  However, when I got it home, I discovered the shank is actually tapered.  It doesn't look like it was cut down from a T-auger.  Were there any boring machines out there that actually took a tapered auger bit?  I was going to take a file to it, but don't know how round I could keep it.  Any suggestions on the best way to turn it down to fit?

Thanks!   

 

[Jim_Rogers]

Have you tried it in your boring machine?

The end looks like it is correct, that it has a dimple for the set screw to lock into.

When we turn any ends we usually try to turn them to .495 so that they'll be just a bit under 1/2" so that they will fit all standard boring machine chucks.

Jim Rogers

[Dave Shepard]

It will be difficult to accurately machine the bit without a lathe. I have several bits that need some correction, and we will do them in a friends large metal lathe. My factory original bits are all really close to .500" and no taper. My undersize bits will have to be built up with weld and then turned true. If it is tapered in the last inch or so, I think you will have a hard time getting the bit to stay tight and centered. There are tapered bits for machine tools, but not for boring machines that I'm aware of.

[Brian_Weekley]

Thanks Jim and Dave.  It sure looks like an old boring machine auger bit, but it has a taper of about 0.52 to 0.57 inches over the first two inches of the shaft.  I'm thinking about putting a die to it that would have an internal thread diameter as close to 0.5 inches I can find.  Then I could just file off the threads to hopefully leave a reasonably round shaft of the correct diameter.  No hurry since I have other bits to use now.  Just looks like too nice a bit not to get into my machine sometime.  I can't picture how you could put it in a metal lathe to turn it down.  Wouldn't the chuck hold it right where you need to turn it?