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11-03-2012, 05:24 PM #1
Removing Motor on Bridgeport J Head Mill
I'm trying to pull the motor off by 1966 Bridgeport 2J2 Head mill, but having problems. The motor quit working a few days ago, so I can't drop the speed to the lowest settings as recommended by the manual:
Consequently, I can't tilt the motor over more than an 1" or so to get the belt off. Also, the instructions say there are two screws that compress the spring. I've removed the cover, and see two deep holes. If there are screens inside these holes, the heads may be stripped off, because no screw driver or allen wrench I own will turn them.
So I'm stuck. Can any of you with more experience than I on old Bridgeport mills please offer some suggesting for getting this motor off. I've already tested the Phase Converter and the power up to the motor. These are fines, so the problems is most likely in the motor or the head.
11-03-2012, 08:16 PM #2
I may do this all backwards but...
I always run the head to maximum speed. This puts the belt on the largest diameter of the motor pulley. Remove the cover from the bottom of the motor end of the head case so you can reach in when the motor is lifted.
I then lift the motor about 3/4 inch and tip the top back so the pulley goes towards the spindle.
The other way is to put two long bolts into those holes you see on the bottom of the motor pulley. they will hold the sliding part from collapsing. They screw into the fixed half of the pulley. I think they are threaded 10-24 ( correction here guys if I'm wrong). Once the screws are in and holding the pulleys, turn the spindle by hand.
A long end mill holder held in by the drawbar gives you something to turn.
While turning the spindle, turn the speed crank to the slowest setting. That should release the belt and let you putll the motor.
11-03-2012, 08:58 PM #3
Good idea trying to turn the spindle by hand. I put a drill chuck in the spindle and an Allen wrench in the chuck. Unfortunately the spindle only turns a little ways (15 degrees maybe). Feels like the belt inside is caught on something.
11-04-2012, 12:24 AM #4
Remove the 'Speed Control Assembly' from the front of the head. Rotate it to unwind the chain. That is the mechainism, that pulls the top sheeve down against the drive belt. Once there is slack in the chain the motor can be tilted back and removed as the belt will be free to slide to the small diameter of the front pulley.