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Thursday, December 20, 2018

A CGE Model 4J70FB 3/4 HP Motor


I've had this old brute collecting dust in a drawer for years.


It weighs 40 lbs. Speed is 1,725 rpm. The shaft is 5/8" diameter with a 3/16" keyway; effective shaft length is 1 3/4". Input can be either 110 or 220 VAC, and it's reversible. Here's a view of the little wiring diagram inside the connections cover.


And here's a view of the actual wiring represented.


The motor would make a fine power plant for an 8" table saw, if anyone were interested in 8" table saws anymore.

Anyway, it's time it got a paint job, and maybe a new front bearing. (The bearing feels like it may be grease starved.)

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Shroud Removed

Four 10-32 x 5/16" hex head screws fasten the shroud in place. The shroud comes away easily once the screws are removed.


Note the two chips in the perimeter of the fan toward the top. Was that done on purpose for balancing, or was it accidental damage? I'll never know.

I'll remove the 3/16" key and burnish the rusty shaft before proceeding.

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A Keyway Flaw

Here's a shaft-end-on view of the keyway.


Note that the keyway is not cut perfectly radially -- it's slightly askew from the radius. That's making it impossible to fit a keyed pulley.

The only cure will be to file the key on one face so that the key has a slightly rectangular cross-section -- the key's 'height' will need to be slightly less than 3/16" to compensate for the tilted 'floor' of the shaft's keyway.

And here we have the key filed down so it fits a pulley.


Note the skewed fit of the key in the pulley's keyway. That skew is on account of the shaft's keyway, not the pulley's.

I have one other pulley that still doesn't want to fit, so I'll have to file down that key even further. The motor has to readily accept any 5/8" bore pulley that's handed to it.

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I got the key filed to where both pulleys fit, and noticed something that may have been faking me out a bit. It seems that a key can exhibit side-to-side binding in a pulley/shaft assembly, even though no sideways binding is evident with the key in the pulley or shaft on its own. (I hope you're still with me; this is difficult to describe.) It appears that slight sideways flaws in the two keyways that don't cause key binding in either keyway alone, may add in such a way that they cause binding when the keyways are mated. In any event, beware. Binding keys can present deceptive characteristics.

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Fan Removal

The fan's hub face resides 2 1/16" from the end of the shaft. The fan is held on the shaft by two 10-32 x 3/8" cup-point setscrews with 3/32" hex sockets.

And here we are with the fan off the shaft.


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Capacitor Cover And Capacitor -- FRIDAY, DECEMBER 21, 2018

The capacitor cover is fastened by two No. 8 x 1/4" round head, plain slot tapping screws.


The capacitor is a made in Canada Mallory P/N 842A466-4, 400 microfarads, 110 VAC. Measured capacitance is about 396 microfarads.


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Dismantling The Motor's Frame

Four 10-32 tie rods with 5/16" hex washerheads hold the motor together. (The head ends go at the wiring end of the motor.) The tie rods are 8 1/4" long. The tie rods have fibre flat washers under their heads. Curiously, one tie rod had no fibre washer, and another tie rod had two fibre washers. Four 3/8" A/F hex nuts complete the fastenings complement. There are no lock washers. Here's a view of the tie rod set.


With the tie rods out, it's time to knock off the wiring end end-bell. Doing that got me to here.


The rotor wants to remain with the rear bearing. I'll have to disconnect all the wiring to free the end-bell/rotor from the motor's frame.

Always take photos and/or make a sketch of wiring connections prior to disconnection.

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Wiring-End-Bell Dismantled

Here's the end-bell with rotor out of the frame.


A bit of judicious hammering got the end-bell separated from the rotor.


And out came the bearing with the aid of a puller.


The bearing is an NTN 6203Z -- 17mm bore x 40mm O.D. x 12mm wide, shielded one side. The front bearing is the same. The open sides of the bearings go outboard, facing a generous supply of grease.

Both bearings are in fine condition and well greased. My earlier sense that the front bearing may be grease starved was wrong.

Anyway, there we have the near complete teardown of the motor. I just have to knock off the front end-bell yet. Once that's done, I'll get on with cleaning and paint preparation, and give the motor a decent paint job. I'll clean, flush and regrease the bearings prior to reassembly.

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Front End-Bell Off -- THURSDAY, DECEMBER 27, 2018

Here's the front end of the motor dismantled. All has been cleaned of grease.


There's a spring washer to bias the rotor rearward, and a shim washer that reside in the front bearing's cavity. The bearing is press-fitted onto the shaft. The bearing's outer race is an easy slip fit in its cavity. There's what I take to be a felt grease seal of sorts at the outboard end of the bearing cavity in the end-bell.

And here's a close-up view of the start winding switch actuator.


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All Done -- MONDAY, DECEMBER 31, 2018

Here's the motor all painted and reassembled.








I repacked the bearings with Canadian Tire's Motomaster Wheel Bearing & Chassis Lubricant No. 28-0422-2. That's great stuff that I'd trust with my life.

The motor went back together easily; I had no trouble with bearing fits. The motor runs beautifully.

Here's a brief video of the motor starting up and shutting down


And there we are -- a nicely refurbished motor. Now I just have to find a use for it.


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