I have a dust extractor with a flange mount, SP 3HP motor, and 13" impeller and would like to replace the SP motor with a 3P motor so I could spin it at 60Hz to get a bit more air through it.

As usual I want to do this on the cheap and have had in my shed for some time a 4HP 3P flange mount motor and I have a spare 4HP VFD ready to go. The flanges don't mate up but making an adapter plate should be easy enough.

The main problem I have is the original motor and impeller use a 24mm shaft and the replacement motor is a 28 mm shaft so the collar on the impeller will need to be bored out. There seems to be plenty of meat in the collar with part of it 57 mm in diameter and the other part 47 mm in diameter so even allowing for a new keyway there is enough there to work with.

Initially I was thinking of doing this on a lathe but the under side of the impeller had nothing to hang onto. The topside has the protruding collar but the the impeller has deep vanes that would prevent any normal lathe chuck from grabbing it. Plus I'm not too keen on working around spinning impeller blades on a lathe. The collar is welded to the impeller and thought about cutting it away and then boring it out and welding back in place but cutting it out will be a PITA and I doubt my skill level will enable me to place it back in its original location.

My next thought was to use a drill press or mill to get it close to 28mm and then a reamer to get a good fit.

One issue I can see is the keyway will cause the drill bit to jolt every time the cutting edges go past the keyway so was thinking of temporarily filling the keyway with a piece of mild steel and tack welding it to the keyway. I will also have to cut a new keyway and the remaining steel in the keyway would make it easier to do that.

Anyone have any other ideas?
Thanks


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