Bridgeport J head 1hp motor replacement

[jdr_chips]

I’m looking for a motor to replace the motor on my 1964 bridgeport J head.



The original motor suffered a tragedy this winter. On a pretty cold day, about 15 degrees, I needed to do some work for a project, so as I fired up the mill I’m looking at the work getting ready to start making chips and I think ‘the spindle sure isn’t spinning up very fast’. Then I looked up at the motor and saw the magic smoke pouring out. I shut ‘er down, but it was too late already. I was running it on a rotary phase converter, which was happy to dump all the current it could (I haven’t taken apart the RPC to see if it also smoked). I’ve since built insulated walls & ceiling around the machine tool area and installed a heater to keep them at least 45 degrees (always too late with the improvements…)



The motor is 230/460 3 phase 1hp, with 2.1" long x 3/4" diameter shaft. The J head is the step pulley type. The current power setup is 240V single phase driving the RPC which runs the spindle motor, but after the smoke I bought a 1hp VFD to drive the new motor to hopefully prevent future sadness.

So now I’m looking at replacement options. I took the motor to a local shop, they said $700 to rewind. I’ve seen kits with adapter plate and motor on fleaBay for around $750. The motor shop guy stocks a 1hp 3phase 56C with a 1 3/4" x 5/8” shaft for $184. I got to looking at the available styles in 1hp 3 phase and found a 143TC that has a 7/8” x 2 1/4" shaft, considerably closer to the original. The current motor is 3/4" shaft that sticks past the mounting ‘ears’ by about 2 5/8”. In looking at the motor step pulley it looks like it was sleeved from 7/8” down to 3/4", even if it isn’t I can chuck it up in the lathe and bore it out, tho the keyway will be some work. The current motor has some of the motor housing sticking about 1/2" past the surface of the mounting ears down into the pulley area.





I’m thinking my best option right now is to replace the old motor and make the adapter plate to connect the 143TC motor. To get closer to the same amount of shaft into the pulley I’ll need to make the adapter plate recess the motor by a bit. I’ve got some 3/8” plate laying around, so I’ll use the plasma cutter to cut a circle about 1/8” more radius than the size of the motor, then drop that circle down 3/8” and weld it back onto the remaining plate with the mounting ears. That should put my new motor face close enough to the old to work.

With no mill getting the bolt circle for the motor mount and the flange holes is going to be more challenging. I’ve got an old 3/4 hp 120V motor with a step pulley on it that I was thinking I might do a quick hack job to mount onto the mill, just so I can get power to build the proper replacement plate.

Any suggestions or comments would be appreciated.

Thanks,

Jeff

[JCHannum]

Are there any other rewind shops in the area? I have been out of the loop for a while, and know it is cheaper to buy than rewind lower HP motors, but $700 sounds excessive, especially if you are just having the stator rewound and doing the dissassembly/reassembly yourself.

[jdr_chips]

They are the only one in town, but Denver, 60 miles away, has several. I'll call them for quotes.

Thanks,

Jeff

[IOWOLF]

Personaly, I would never put a bridgy type motor back on a mill.

I would make an adapter plate for a c mount motor which are cheap.

But thats an opinion, and it is My opinion and what I would do.

[jdr_chips]

I got a few more phone quotes from Denver shops for a rewind: $525 + bearings, $600 + bearings, and $300 + bearings. I'm thinking the $300 one might be worth it, but I'm betting he will increase the price once he actually sees the motor, since it has that enamel all over everything.

Thanks,

Jeff

[Bill Pace]

I'm with wolfie, -- I'd get a c-face motor... easily found and should be in the $100 (or less with 3ph) range, and make up an adapter plate.

[lazlo]

+2. You can buy a Baldor 1 HP, new in box, on Ebay for $50 - 100.

I'd go for a 1 1/2 HP motor, since that's what the later J-Head's have, but maybe that's the Tim Allen in me...

[Forrest Addy]

The shaft is the main hessel with replacing a BP motor. You can whip up a suitable flange from steel or aluminum plate for a C face motor in a couple of hours but the long shaft...

Best approach for a long shaft to crop the existing shaft, weld a stub on it, and machine it. This is skilled work but doable. Be careful not to involve the bearing fit and the seal/flinger diameter and to ensure a 100% weld. I use a full V weld prep, back grind the root pass, and tack on run off tabs. So long as the stub material is mild steel, you do a post heat of the HAZ to about 1200F, the rough stub is 1/4" or more larger than the finished size, and welded on halfway straight the rest is plain welding and machine work.

[Bruce Griffing]

I would extend the shaft of a standard motor, per Forrest's suggestion. You can get very good motor values at the following site - here is a link to a candidate motor -

http://www.surpluscenter.com/item.as...tname=electric

I bought a new three phase base mount motor for my lathe - 3hp - for $79.95 plus shipping. It is a nice WEG motor. I have had good luck with them on several items.

[jdr_chips]

Thanks for the link Bruce, that is a the lowest price I've seen yet.

I'm definitely leaning towards replacing the original motor as suggested by everybody so far.

Thanks for the shaft extension techniques Forrest, it sounds do-able.

Jeff