Taking a bit of a break from filing ( lots of it ). I have started on QR no2 and have now shaped the lever, still to be cut off and polished to a chrome finnish though. Pic attatched.
Andy,
You are indeed right in that Arca use 45 degree for their dovetails. Before starting out I thought I would check for a drawing. Arca's plates are shown as 32mm wide into the clamp with 45 deg dovetail. My preference is for 60 deg based on workshop theory. Most lathe top slides have 55 deg and they deal with major forces so I opted for 60 deg as being the nearest. Saved having to buy a 45 cutter for £25, and I am not likely to lash out on the storebought QR plates for these, as I can make my own for a couple of quid each. So my plates are 38mm wide into the clamp with 60 deg dovetail ( closest to 55 deg ). May have less contact area for a given height, but the shallower angle makes the dovetail stronger and in practice the clamp is really tight.
Something I did come across in that bit of research, was that although a number of manufacturers state Arca compatable, I found this link that shows this is not necessarily true.
http://www.afximages.com/stuff/arca-plates-xref.html
Don