Is there something like an inverted drill bit

I would like to make sure that you know that there are shaft adaptors that are sold commercially.

i

There are rotabroaches that are 1/2" ID but it would be nearly impossible to use one in a drill press and have the shaft come out concentric with its axis. You are in deep doodoo, pal. Suggest you buy a motor arbor that bolts on which effectively does what you need, rather than wrecking your motor. - GWE

"Grant Erwin" wrote: (clip) it would be nearly impossible to use one in a drill press and have the shaft come out concentric with its axis. You are in deep doodoo, pal. (clip) ^^^^^^^^^^^^^^^^^ Not necessarily, Grant. Maybe he is building a vibrating table.

You could bore out your existing sheave. Purchase a long 1/2" steel bolt, the body of which is a tight 'slip fit' to your sheave.

(One that looks like the second from the left in:

Cut off the bolt threads. Cross drill the body of the bolt off center about 1" from the cut end, (start with a center drill. Size this to fit a sharpened 1/8" tool blank. End drill and tap the axial center of the body to accomodate a 1/4" clamp screw. (Use a 'pulley tap')

Adjust the tool blank to protrude say 0.0615" above the body of the bolt and liberally apply cutting oil. clamp the sheave in your vise using blocks of wood to spread out the force. Insert your new piloted boring tool and crank it through the bore of the sheave with your 1/2" breaker bar or long handle ratchet. Use an adjustable reamer in your power drill to open up the ID for a cold slip fit to your motor shaft.

Viola! one properly sized sheave.

--Winston

It's called a file

Or clamp the boring bar (toolholder) on the vise movable jaw. Bolt the motor to the bench such that the shaft is exactly parallel to the vise screw axis. Run the motor while using the vise screw to move the tool along the shaft.

The usual tool that acts like an inverted drill bit to turn something down

is a lathe

i cant think of many ways to rig a tool up

The name of the "inverted drill" you are looking for is called a Hollow Mill. Check industrial suppliers like MSC.

THIS is the kind of answer I was hoping for. Thanks very much!

I figured I'd end up needing to remove the shaft to do anything to it.

Thanks !

Yeah - that's what my initial thought was, too. Thanks !

Cool! I will do so! Thanks!

Yep and I understand that that is probably the best over-all solution. But thanks for the help! JCD

Yep - I figured that! I seem to figure out a lot of this stuff *after* I post the questions!

Yes, and good idea! JCD

Thanks. You da man.

most of the other advise is right on, but - a long time ago I did something similar by running the motor and bringing a grinding wheel (powered and running in opposite direction) up against the shaft - worked well enough for my purposes, though certainly not very high precision

Bill

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Me too, and more than once in my life.

I'm assuming that you didn't head for a shaft adaptor because it would extend the shaft further than your application can accept.

Depending on what you're trying to do, if it's just a small die cast v-belt pulley or something similarly imprecise that you intend to put on the shaft, then carefull application of a flat file with the motor running and FREQUENT checking of the diameter at several points along the length you are reducing will probably be good 'nuff.

If you're going to be spinning a larger diameter weighty load you'd be better off biting the bullet, taking the rotor out and bringing it somewhere where it would just be "the matter of a moment" to have it turned to size on a lathe.

Jeff