On Sun, 2 Dec 2012 17:44:39 +0000, Ian Jackson
wrote:

snip
The instructions for the Radcaps caps are a bit strange,

agreed

I also note that the cap has a 8mm x 5mm slot. I suppose that this might
be OK for a 1/4" square spindle - although it would be gripped only on
the two opposing 5mm sides - and as 5mm = only 0.196", it would
certainly be a pretty firm grip (possibly guaranteed to crack hard
plastic).

These show "assorted spindle drivers" but are dearer than complete
valves.
http://www.inest.co.uk/products/Orac...ator_Cap.a sp