Now here's an interesting one. I'm in the process of making a leather bellows for an old arca swiss f-line 5x7. Obviously, sizes of he bellows frames are quite critical. Initially, I had envisioned hacking an existing frame for the front and a new one for the rear from aluminium sheet. However, I figured that once I would be cutting sheet anyway, I may as well also cut a front frame. In comes the surprise. Running a quick measure with my rusty callipers, the following come up.

Rear 5x7 bellows frame:
thickess 2.5mm
outer 215mm
inner 187mm
(frame 14mm wide)
corners rounded at 90 degrees 8mm

Lens plate measured for front frame:
thickness 1mm
outer 110mm
corners rounded at 90 degrees 5mm

Well, so far so good, no surprise here... Then I traced these dimensions on paper so I could trace them onto the respective aluminium sheets. Of course I do the outside cuts on my rotatrim. But then...

The carefully traced paper dummy of the 110mm lens board is up first. I cut it, all good. However, on the rotatrim scale that is meant to be accurate...

110mm lensboard outer 110mm (?!). I of course put a real board on it and sure enough, I'm 2mm short of 110mm on that too. I find this rather hard to believe as everything arca always seems so meticulously and flawlessly executed. To solve this conundrum, I would be much obliged if someone more knowledgable than myself could give me te exact measures of:

The 110mm lens board (which I will assume is 110mm except my rotatrim thinks otherwise)
The exact dimensions of a 5x7 bellows frame (f-line)

Thanks a million for this and have a great day!