Anyone out there crazy or curious enough to try the knob from a VPI cleaning machine as a clamp on their VPI table? I had 2 VPIs but 1 came with no clamp so I switched the clamp between tables. Have sold 1 and now have no threaded clamp. Just checked and it does seem to thread, though it takes a lot longer to work its way all the way down. Not sure if there is a huge audible difference between the expensive clamps and the cheap plastic knob but I await stories from those with significant experience that have tried.
It will clamp the record down, but it won’t do what the appropriate clamp will do. Which is to have the record firmly connected to the platter. 
In other words, get the right clamp.

good luck
It should be noted that the knob is almost the same size as the original translucent disc that came with the early HW19 MKIIIs. It also screws all the way down and seems to put pressure on the lp label. I have now tried it over 3 lp sides with no egregious problems noted. At least someone has tried it. Soon enough I will bite the bullet and try to acquire an original disc and small knob or a more recent large delrin clamp. Then I can actually do a direct comparison and even entertain a blind comparison. Thanks for the replies.
It is the exact same clamp that came with my HW19JR turntable back in the 90's.  I had a VPI record cleaner and the 2 clamps are identical.  Their best clamp is the stainless/delrin clamp.