During alignment of a vertical motor, 0.005" radial movement of the motor shaft was observed when pushing lightly on the shaft. This made it impossible to achieve 0.002" target alignment tolerance.

The lower bearing is 6320 bearing. Max internal radial clearance 2.6 mils. An EASA recommended lower bearing housing fit would be 0 - 2 mils in the shop. This gives worst case 4.6 mils radial movement. I believe possibly the housing clearance has enlarged a little during operation. Will post vibration history when I have time.

My question - does this seem unusual for you. Have you seen similar radial movement (0.005") when aligning vertical motor with large deep groove bearing (like 6320) at the bottom?

elecricpte, I roughly remember such issue in sea water intake pump motor long back. I recall we made sleeving in bearing housing for some motors and it was very painful exercise, but successful. These bearings show any sign of outer race rotation ? How much is vibration reading for motor solo run trial ?

Would not surprise me if the houseing bore is worn.

My experiences suggest (except in rare instances of ball/roller bearing seizure) "spin" is actually creep, resulting from the famous NOT one directional load in the bearing seat fitting charts. The mechanism is a friction drive similar to an internal gear pair (http://www.fi.edu/time/Journey/Time/Escapements/internalgear.gif) with a ratio ~ .9997
Vertical shaft motors' non thrust bearing are highly susceptible to this, and a rigid coupling to a pump shaft would practically guarantee it will happen. Seems like the only mechanism resisting outer ring creep would be the wavy preload spring, and it is not well equipped to do that.