Hi Michael
Thanks very much for that HSE link, interesting reading. And an interesting point you raise about the wheel width (thickness) at the bore. In that HSE guide, the section on mounting and spindles states the following:-
Spindles
33 The spindle should be long enough and threaded to a sufficient length to
ensure that when the wheel and flanges are mounted, there will be enough thread
for full engagement of the nut on the spindle. The thread should extend inside the
flange but not into the hole in the wheel.
The last sentence is interesting. I just measured the unthreaded portion of the end of the Clarkson spindle and it is around 10mm. So, I deduce that a wheel should be no wider (thicker) than 10mm at the bore, else a portion of the wheel bore will sit on the threaded portion of the spindle.
So it seems to me that it is not right to put a 6 inch diameter wheel, 20mm wide on there (which is in fact what I temporarily did with unease).
Steve