When the PTO is disengaged... that little "friction plate" is a brake... it should be rubbing on decently hard when the PTO is disengaged. It slows the implement down during normal disengagement from running, but it also acts as an emergency brake for the PTO if you pull back on the PTO lever fully.
If you notice there is a threaded bar at the top that connects to your handle. You can adjust your clutch application pressure by adjusting that nut and pintle..
I can tell you that using an orbital sander to take the glaze of the surfaces will fix a lot of problems that are encountered. I can see the thickness is just fine !!!!!! Can tell you that the ball bearing should be check as they can cause the problem too.
The friction disc that was beginning to separate from the rest of the the clutch plate assembly had completed separated on my unit and shattered into pieces on my Wheel Horse. I just wonder if replacing just the disc with one intended for a different make/model unit but having the correct dimensions for use on the 520H clutch plate. Not sure what adhesive exactly but that won't be a problem.
