Triangular gib key.

[olderdan]

This was an invention by a W. D. Urwick C.Eng., M.I.Mech.E. and an in depth article can be found at Impetus Metalmaster

I thought this would be worth posting as don't think it is as well known as it ought to be and has a lot of advantages over the more traditional square key found on most machines.
For a start wear is not a problem as it is self adjusting, it also maintains radial alignment on round column machines to a high degree of accuracy as well as a clamping function. Mr Urwick was in my opinion a genius who had his own way of thinking and doing things. (remind you of anyone we know?).
The only difficulty I can see for the home workshop is machining the bore for the key, o/k in cast iron or alloy but steel would be more difficult but not impossible.
Maybe worth thinking about at the design stage of anyone planning a build.