Skinny Bushing?

[epanzella]

I'm in the middle of setting up my VFD on my mill and got thrown a curve. The old motor has a .945" shaft with a 1/4" keyway and the new 3ph motor has a .875" shaft with a 3/16 keyway. I don't have a problem making the stepped key but the bushing works out to be .035" with a keyway slot and I'm not sure of the best way to make that. I could use a silver bullet if any of you guys have one.

 

[682bear]

I'm assuming this drives a pulley?

I would turn a piece of material to fit the ID of the pulley, JB weld it into the pulley, then bore the ID to fit the motor shaft. Finish the keyway last.

The reason for JB welding it into the pulley is so it doesn't collapse when you cut the keyway through the sleeve.

-Bear

 

[Jim F]

Here you go.

 

[talvare]

I recently had to do almost exactly the same thing with an old cast iron pulley that you're doing. I bored the pulley just large enough to eliminate the keyway, then turned a piece of steel .002 larger than the bore and heat shrunk it into the bore. Then bored it to size and broached a new keyway. Worked out very well.
Ted

 

[macardoso]

I'd agree with the above statement about relining the pulley. The new motor shaft is a more standard size so you are modernizing the design. My only addition to @talvare would be that once the liner is installed, drill a hole right at the boundary between the original pulley material and the liner and install a press fit dowel pin (180 degrees opposite the spot where you will broach the new keyway). This is a quick and dirty way to add a "key" which prevents the press fit from slipping under extreme torque. Loctite 609 (Green bearing retaining compound) is also an excellent way to do this. The strength is tremendous when the parts are a tight fit and not too hot.

 

[epanzella]

I ended up cutting some aluminum sheet for shims. I left them short so they left the keyway exposed without any further action. I was on a roll but when I went to mill the stepped key I got a rude awakening. Because I was working on my mill pulley, I had NO MILL! I broke out my old milling attachment and mounted it on my lathe but was unable to hold the 5/16 key in a way that would allow me to machine half of it to 3/16". So out comes my old mill vice and I tram it to my milling attachment. It has stepped jaws and I STILL couldn't mount the damn key as they wouldn't close enough. I finally made a holding fixture for the key that went into the mill vice which went onto the milling attachment which went onto my lathe. The key fit like a glove but I couldn't believe this little part took me all morning to make. It probably would have been quicker to file it by hand out of an old cylinder head!