Vari-Disk Pulley Repair

I purchased a 2hp BP a few weeks ago and going through it from top to bottom. The motor pulley bushings were wiped out! They came out in pieces along with the keys. Never seen any that bad.... The operator must of been wearing hearing protection from the noise!

Anyway, the motor shaft has about .003 ware and the pulley is a little out of round. Needless to say when new bushings a in place there's to much clearance.

I want to grind the motor shaft down a few thousands and bore the pulley out a little to straighten things up, and make a couple of special bushings. I have more time than money.....

I don't know about plastics, but there seems to be several types of Delrin materials available. McMaster Carr has different ones listed..... Acetal, PTFE, and Glass filled...

Which one do you think is the closest to the OEM material? I would suspect the running clearance should be zero or darn close..

Looking for a few good suggestions. I know with a little help from the group I may be able to pull this repair off and save some money.

Thanks for the help.

aj

Previous owner at some point did what you described to the sliding pulley on my machine. It didn't work. They bored the pulley and made a fabricated plastic bushing, not sure what plastic but it was off white. The fix was a 4130 sleeve pushed in with green Loctite, re-bored to correct size and a new key slot. The motor shaft was acceptable and it went back together with stock plastic bushings and glue.

Thanks for pointing out the epoxy will make the bushings tighter. Simple as it is, I just didn't think it out that far.

I tried the new bushings in disk (without glue) on the motor shaft and I could wobble it a fair amount. The epoxy shouldn't have any problem filling up .003 or so to tighten things up.....

Happy New Year!

I bought a kit off ebay that came with iirc urethane bushing and epoxy. My Bridgeport is pretty much as quiet as a new one.

Big B

I used leftover epoxy to glue two mixing sticks together. As the epoxy cures the bond between the sticks firms up. Thats when it is time to move the vari-disc on the greased shaft. Move the vari-disc just enough to be sure that any epoxy that might have ozzed out does not bond to the shaft.
I preferred at least twenty four hours or more before reassembly.
John

The task worked out better than I expected. Cleaned and bead blasted the pulley so the epoxy would grip good. Roughened up the bushings with sand paper, mixed up the glue and assembled.

Oiled up the shaft and pushed it through the pulley. Wiped off some of the mess and put the motor shaft in the lathe and spun slow to check run out on disk. Put a couple of heat lamps on it too.

It seemed to run real straight without much run out. After about two hours I put the shaft in the arbor press and moved the shaft in the pulley to make sure it would come apart. When I left the shop the pulley was "firm" on the shaft but could be moved by hand. I left a shop light on it tonight to help things cure up....

Hopefully it will live for a good while. Thanks guys for the help and suggestions.

Aj

Which key did you use?
The 2 hp motor key looks like this and has a metal back up:


The 1 1/2 hp motor key is just plastic:


Epoxys have different cure rates. The epoxy provided with the replacement bushings has a fast initial set.
The epoxy for way liner has a 'slow' initial set and achieves maximum bond strength after seven days at
70 degrees.
The shop had eight Bridgeports and other machinery. When running three shifts the bushing replacement was completed the same shift and the mill was ready for use for the next shift. These repairs would only last one to two years. I think this was because that although the epoxy had 'hardened' it was still in a plastic state and the pressure from the drive belt would affect the final set diameter of the bushings. Later I changed the turn-around time for assembly to twenty-four hours. The repair lasted much longer.
Usually motor and front vari-disc bushing were replaced as a set. If the drive belt was worn or damaged it was replaced. Guys would stall the spindle when driving large taps. The motor would still turn and burn a small spot on the edge of the belt. Over time this would develop into a flat spot that would eventually cause a vibration.
I thought this was a source of bushing failure along with short epoxy cure times.
The replacement belt for years was a Goodyear belt. I switched to a Gates belt for the vari-disc drive. The Gates was not as soft as the Goodyear belt, a little louder at high rpm but had a longer service life.

John