p.2 #1 · Reminder: Don’t use Arca plates without safety pins
In the precision manufacturing world, in which I spent my entire working career, a 'dovetail' feature is measured by the distance over two identical pins that are resting in the dovetail cuts, as shown in sketch one below. I've never seen such a specification or tolerance stated by A/S, RRS, or any compatible manufacturer. My research both online and from measuring my drawerful of currently unused "A/S compatible" mounting plates as well as those on my large assortment of cameras and lenses with a foot, is inconclusive because of different geometries used. Even RRS had two styles, one older with a dovetail that is symmetrical rather than including a zero degree flat surface as one of the dovetails surfaces. Then there is the variation of thickness of the plate below the dovetail which rests on the clamps inner bottom. I was certainly hoping to find an engineering drawing from RRS or A/S that showed a dimension over two pins, but that did not happen.. RRS published the drawing of their geometry in their own patent for this design but it, too, did not show such a dimension, but rather more of a CAD drawing, seen below. I was determined to get to the bottom of this but, alas, there is just not enough data available nor useable spec from different manufacturers, I've given up trying. The RRS drawing does not use the dimension over pins method to measure for inspection. They have provided a calibrated location to use as a measuring reference point (the post-finish dim shown in red) if you are using a CMM (Coordinate Measuring Machine). A good CAD designer could start with that sketch and add the right circle features to allow us to measure over pins. That's not me today.
p.2 #2 · Reminder: Don’t use Arca plates without safety pins
As an alternative to that sort of analysis, which of course has value, it would also be useful to see if anyone actually has experienced a bracket from one high quality manufacturer that did not fit correctly and securely on the head from another high quality manufacturer.
I can't help with that since my various combinations using RRS, Acratech, and Kirk all work together fine with no issues at all.
p.2 #3 · Reminder: Don’t use Arca plates without safety pins
The North American manufacturers adhere to a different dovetail "standard" than the actual Arca-Swiss design which is typically followed more closely by European and Asian manufacturers.
