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Mill conversion to 3 phase

DavidR8

DavidR8

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I started tearing apart the mill to do the motor swap to 1.5 hp 3ph.
I don't have a puller so I had to improvise with some all-thread couplers and 3/8" bolts which I used to jack to pulley off the shaft.
As I got close to getting it off the shaft I ran out of thread on the fully threaded bolts so I ran them back in and put the shouldered bolts in the other end.

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The pulley was so tight I thought I was going to strip the threads. Even after heating it up with my propane torch it was a struggle to make it budge.

IMG_6074.jpg

Finally got it off. Discovered what there was no keyway in the pulley, just a setscrew that seated in the keyway.

I think I'll be shopping for a new pulley as the bore is 15/16" and the new motor shaft is 7/8. I suppose I could bore it out and make a bushing but I have no means to broach the keyway.
 
Lots of youtubes on manually broaching keyways on a mill or lathe. I just did one on my lathe.


Doubling the HP eh. You're gonna have to Hilti that mill to the floor now.
 
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@YYCHobbyMachinist I’d go for that except the pulley is steel. Think it’s possible still?

It’s 1.5 hp. I currently have 1 hp. I increased the hp to compensate for loss of torque at low speeds.


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Had the set screw galled the shaft and made it hard to remove the old pulley?

Are you looking for a single pulley or a 3-step? Since you have the VFD, I'm guessing the multi-step pulley isn't really necessary?

If you were to bore and bush, how much 'meat' is there before cutting through the bottom of the smallest pulley?

Craig
 
There was no galling that I could see or feel. I think it was just 40 years of never having been removed that was the issue.

Boring shouldn’t be an issue because the motor shaft doesn’t extend much past the height of the bottom sheave.
There’s lots of thickness to accommodate boring to accept a bushing.

I’m inclined to look for a pulley the size of the middle sheave. The one thing that I’m concerned about is finding a new pulley that has a long enough shaft to be the same height so belt tracking isn’t affected.


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If you’re thinking of sourcing local, try Troy Electric or the guys over on Bridge St — Osborne Mechanical?. Troy had a nice selection of steel pulleys when I needed one for my Keller. Western Equipment maybe as well.

-frank

failing that, you could always turn one on your lathe.....;)
 
francist said:
If you’re thinking of sourcing local, try Troy Electric or the guys over on Bridge St — Osborne Mechanical?. Troy had a nice selection of steel pulleys when I needed one for my Keller. Western Equipment maybe as well.

-frank

failing that, you could always turn one on your lathe.....;)
Click to expand...

Thanks Frank, I wouldn’t have thought of Troy Electric.
Western Supply was going to be my first stop.

I may try turning a bushing and see how that goes. I have some 1.125” 1018 that would probably work ok.


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When I did my conversion I sourced my pulley from Canadian knife maker supply . The pulley was a 2-3-4 and 7/8 bore

Not cheap, but did the job. Pulley was 85 or 90 bucks

Www.knifemaker.ca


Search for pulley
 
I decided to make a bushing.
Measurement indicated that I needed to go larger than the 1018 I had so went with some 1.25” 6061 aluminum.
Bored out the pulley then turned the aluminum to match.
Bored the aluminum to .875” to match the new motor shaft.
Cut the key way using a 1/8” cut off blade laid flat in a tool holder.
I didn’t bore the pulley deep enough so I have to fix that but I’m pretty happy with it.
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YotaBota said:
Looks good, is the bushing press fit into the pulley?
Click to expand...
Yes, it's a pretty snug fit on both. I can pull the pulley off but I can't easily remove the bushing without a puller. I may have to invest in one...
 
Seems kind of odd that the pully has no keyway? What does the pully set screw engage on your bushing to keep them from spinning?

I take it you cut the bushing keyway on your manual lathe. Well done.
 
YYCHobbyMachinist said:
Seems kind of odd that the pully has no keyway? What does the pully set screw engage on your bushing to keep them from spinning?

I take it you cut the bushing keyway on your manual lathe. Well done.
Click to expand...

YYCHobbyMachinist said:
Seems kind of odd that the pully has no keyway? What does the pully set screw engage on your bushing to keep them from spinning?

I take it you cut the bushing keyway on your manual lathe. Well done.
Click to expand...

Thanks, cutting the key way was a real challenge as the cutoff tool flexed and the sides of the key way were not parallel. Some file work corrected that.

The set screw engaged the key slot on the old motor shaft. This time I’m going to drill a small dimple in the bushing for the set screw to seat into.


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I took some time last night to connect the VFD. I used 14 ga THHN from VFD to motor.
Motor is silky smooth after tweaking some setting on the VFD. I still need to source a 2K pot so that I can put the speed control on the mill.
Sadly my bushing has about 30 thou runout so I need to remake it or shell out for a new pulley. I think the problem is that the keyway at the bottom of the bushing is not as deep as the top so it's wedging the bottom out slightly.
 
David I bought a large assortment of pots on Amazon. If you can wait for Canada Post to deliver one I'll send it to you. I'll never use all of them in this lifetime
 
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