I'm working with an alignment training exercise that uses a 1/3HP motor and the driven shaft is 5/8" mounted on two pillow block bearings to simulate a driven component. So this is a relatively small project.
Regardless, whenever we take our measurements and plug those values into our formulas, it takes around six or more attempts before we get it within our 2-5 mil target.
We use the following methods in our exercises:
1. Rough Alignment
2. Rim & Face
3. Reverse Dial
4. For the math, the majority of our formulas come from Tommy Harlon's, A Millwright's Guide to Motor/Pump Alignment. I've used formulas from other sources just to compare and the outcomes matched.
Usually what will happen is we make a correction. Even though the correction is in the right direction, it's usually more than necessary. Then we repeat measurements and calculations on make another, slightly less, correction. This goes back and forth, usually narrowing the gap, until we get within tolerance.
I've checked the setup and our values entered into the formulas are correct, as are the distances from indicators and mounting feet. Not having a lot of experience with these techniques, I was wondering if this is normal.
Any input would be appreciated.