I took some pics (btw, all the pics can be clicked on to get larger image) of the plates in an attempt to see those “burrs” on the holes or slots that are implicated in the hump or STA (self torque amplification) event. I think having my sketch diagram of how the plates and spacers are arranged would be useful here:
Here is the stack as it comes out of the VC. Note that the circlip and shims are not on the end of the shaft. Also note that the top plate is not held in the stack by the circlip, but rather is pressed against the endplate when installed.
The reverse side of that top plate, obviously worn.
And the slotted plate below.
Now remember, these two top plates are not spaced apart. The next plate however, is spaced from the slotted plate you see by approx. 0.025″. Mis-focused on this pic, but included it to keep the arrangement clear. See the wear on it even though it is spaced from the plate above?
Here, with the above plate beside, slotted plate turned over.
Here are the adjacent surfaces of another pair, same arrangement as the worn pair above, ie has spacer separating them. Note that they are not worn.
Now lets get a better look at the punched holes.
Closer, I’d say there was a raised rim, very subtle.
And a shot of worn plate holes. I think you can see where the rim/burr whatever you want to call it has been worn.
I only had time to get one close up of the slots in the other plate type, no rim evident on this side at least.
Well, this exercise demonstrated, to me at least, that there are burrs on the punched holes. As to the role of these burrs, I will deal with that in part 3.