Measuring Liner Thickness

Q: Is there a non-destructive way to measure liner thickness in our centrifugal disc finisher? I believe the liner is made from polyurethane.

A: If there is a removable door in the side or bottom, you may be able to see how thick the liner is at that point. In addition to that, run your hand around the bowl, feeling the high and low spots. Find a spot that you judge to be the thinnest and drive a small diameter nail into it until it hits metal. Mark the nail at the liner point with a scratch or some permanent ink, then pull it out and measure. When your liner gets down to about a quarter inch, do these measurements at least once a month.
Most new liners are a half-inch or more thick. They wear a long time until they get down to about one eighth-inch thick, then wear accelerates. It is a good idea to schedule relining when you get to this point. Allowing the liner to develop holes will quickly lead to severe damage of the weldment. Most machines have to be sent out for relining, so plan at least two weeks downtime, or buy a spare, lined bowl.