Snydremark wrote in post #11140743
Great images and info, thanks. Note the emphasis I added to your post.
The problem is that the new fastener has a 'spacer' on it that makes it so that the bolt doesn't seat in far enough into that counter-bore that you call out. Therefore, the nice, slick nickel plating is in direct contact with the tripod receiver and allows the plate to slide even after the lock lever(s) are snapped into place.
If you take a measurement of the bolt head on the original fastener of the 488RC2 plate there, you'll find that it's .196in (5mm) high. When the bolt is seated into that counter-bore, the distance from the surface of the plate to the top of the bolt head is .157in (4mm). This leaves, roughly, .028in (.711mm) of clearance between the bolt head and the tripod receiver if the overall depth of main the cutout is .182in (4.66mm)
On the T1 fastener, the bolt head is ALSO .196in (5mm) high, but there is an additional 'spacer' on top of that [Seen in the op image] that is another .039in (1mm) high
and it's this spacer that slips into the counter-bore. This leaves the entire .196in (5mm) height of the bolt head sticking above the plane of the qr plate's surface.
If you then factor in that the main cutout under that plate is .182in (4.6mm), you have .014in (.355mm) of the T1 fastener extending past the cutout and giving "slip" to the whole unit when it's mounted. .014in (.355mm) is a very minute amount, but when compressing a nickel plated surface down onto another, hard surface like this it's enough to cause slippage.
Thanks for the assistance with this, btw!
Numbers here are reference, (mine) measured with a ruler and converted to decimal/mm manually; not measured with precision calipers and may not be EXACT. But they help illustrate the problem.
please log in to view hosted photos in full size.
I took the liberty of making some annotations on your image so I can be sure we are both talking about the same parts.
The parts of both screws that is .196 (5mm) I marked as 1 and 2, correct? The "spacer" is no. 3, and you're saying this fits into the counterbore. What is the diameter of the part at no. 3 and how does it compare to the through hole in the plate?
Does the shoulder at No. 3 fit into the through hole in the plate? If it doesn't, and I think it should, then that would cause the problem you are describing. It would also mean you might be a victim of "tolerance creep."
Every manufactured item is built to tolerances because it would be physically impossible to make each item exactly the same. Sometimes dimensions creep to the top of the tolerance and and sometimes to the bottom of the tolerance. If the hole in your plate slid toward the small end of the tolerance and the Black Rapid T1 crept toward the top of the tolerance, then it might not fit as it was intended. Neither part is defective in itself but together they don't work.
Does this make sense?