Repair question: Can you reinstall a shading coil?

I've seen attempts at repairing shading coils, but I've never seen one that lasted. The originals are pressed in under high pressure to where the coil deforms into the slot shape, which is usually slightly under cut. So if the coil breaks out, the slot geometry has likely been compromised and can't be repaired. Glue / epoxy will not stand up to the impact vibration for long. Here's a post from someone who did one, but I don't know how long it survived.

http://www.garagejournal.com/forum/showthread.php?t=45234

More important though is that you have experienced this more than once? That alone is cause for some major forensic investigation. Broken shading coils are not common, most people in our industry never see even one. I was in the contactor business at one time so I've seen more than most, but that's still only a handful. I would be very suspicious of there being something about your application that's causing this. A likely culprit is "chattering" of the contacts. That can happen from the coil voltage being too low, or something in the control circuit that is "bouncing" and rapidly energizing and de-energizing the coil. I've seen that on improperly designed float switch circuits for example.

Another common cause is from people manually closing the contacts by pressing in on the armature window, thinking it is a "Go button". It is NOT!

When you do that on a large contactor like a Size 3 or 4, the contacts are going to try to separate when current passes through, because they design the current path like that on purpose. Current flows through what is essentially a horse shoe shaped path so that the magnetic fields created by the current try to force them apart. The coil is designed to overcome this force, but when you push that armature closed manually, your hand can't exert as much force and the contacts separate slightly. Then the current drops, the force weakens, you push it closed again, all in fractions of a second, repeat for as long as you hold that button. All the while, the parts are vibrating open and closed, 120 times per second. It's beating the parts to death!