Great question and hopefully i can answer correctly. The centering pin (teflon i believe is the material if i remember lloyd right), serves the purpose of ensuring as the platter floats on the air between the plates (very small clearances) that it stays centered and does not move side to side as the platter turns. Remember the belt will put a slight force on the platter so sufficient friction exists to spin the platter. This means the platter pulls slightly towards the pulley attached to the motor. Now if the pin is slightly worn, but the platter is perfectly level and balanced, no major problem because the force is parallel to the platter and does not cause wobble. But if the platter is not perfectly balanced, then as the heavy side spins, the clearance will be lower on that side versus the light side. Again if the center pin is perfect, and the imbalance is low, then you do not see much if any deflection because the imbalance is just offset by a little friction on the pin. Since teflon has very low frictional properties, you do not see much impact. in fact you will be able to determine this if you carefully reduce the platter air pressure just to the platter just rubs. I found that if you listen carefully the imbalance will be an rhythmic sound and not continuous. if the platter is perfectly balanced the sound will be continuous. I know this sounds a little black magic but it works. If the platter is off balance you compensate by adding more air pressure which lifts the platter a little higher thus offsetting the imbalance Again you will see this by looking at the top of the spindle. It wobbles.
Now there is one other possibility and that is the spindle is bent slightly. If that is the case, the spindle will wobble but your tone arm will not move up and down. Look at it carefully. You also can get a carpenter square to determine if the spindle is bent.
hope this helps
tomg
