How to straighten a bent motor shaft.

[cogwheel1]

I posted earlier that I had a KD45XL that came with a bent shaft. It was only bent from the case outward, probably dropped at the factory and shipped anyway because the package came to me undamaged. I was sent a replacement, but needed two motors for a 42" twin Cat I am building. I'm sure there are a lot of ways to do the repair--I had several in mind. Just for giggles I made a tool out of a 10' piece of hard round 3/8" stock I had. I bored one end to the 6mm of the motor. I chucked the motor housing in my lathe carfully and spun it to check for trueness. With the lathe off, I brought the live center over as a guide. With the 10" rod on the shaft, the bend is exaggurated and I used the leverage of the long rod to gently bend the shaft until it was lined up perfectly with the live center. It took about 5 minutes or less and it is perfectly straight. If you get it straight with a 10" extension--its perfect as a 3/4" long shaft--- believe me! Some may not agree with the repair, but it spins free and feels in balance and I now have a second motor for my project. I don't know if this can be done on a mini Lathe, but mine is full size. Some of you may want to give this a try if you have a motor that may have been dropped or bent in some other way.
Russ

[tharmer]

Good idea but I'm sure you meant 10 " steel. I tried it with 10' but the weight of it bent the motor shaft about 30 degrees (just joking).
-t

[m4a1usr]

I remember your post. Glad you decided to take on the chore. There is nothing wrong with attempting something like that. You had the tools, didnt have to repair the motor since a replacement was sent. But I would be wary with something like this especialy if your project involves a high rpm application. The movement you see and the imbalance you feel at low rpms is nothing compared to what could be seen once this motor is spun up. And I would put on the end bell some sort of reminder of what was wrong with this motor so that in a couple years (hopefully! ) it will jog your memory to keep a wary eye on it. BTW I would pin the rear end bell instead of trusting the factory glue job. If it vibrates out during use the motor and your speedo will destroy themselves. Just my dos centavos.


John

[cogwheel1]

Ok, OK, 10". Hey it was 1:00 in the morning!! I guess size does matter after all.

I'm not sure I made it clear that there is no movement at all in the shaft and no vibration at all--at least now, when I ran up the motor. That was the point of the 10" rod, so that I could make absolutely sure it was true. If the shaft were out a few mm's at the tip, then it would be out maybe an inch at the end of the 10" rod--more or less, (I didn't do the math-just an estimate). After straightening it, it wasn't off even a mm at the end of the 10"s. It was dead on. I doubt I would even have as much chance of a failure, as with some factory installations that I've seen where the motor was slightly misalligned with the drive tube.

Russ

[tharmer]

Sounds like a good and proper fix.
-t

[cogwheel1]

I guess time will tell. I'm going to run it in this twin 43" Cat I'm rigging. If it grenades, I'll let everyone know that my fix was a bad idea, although from other posts I've read, the motor doesn't sound that great to start with, KB45XL).
Russ