John thank you. – I think I can see how it works. But cannot see how to set up, if it is possible for a specific radius.

Perhaps I am seeking a method as opposed to the unit recommendation. – If the angle was set and a flat ground on the tool one side then swung round to grind the same angle on the other side. It seems this would give a reference edge and then `incrementing in` by the desired radius and carefully swinging between the two angles manually (or to pre-set stops of some kind) You could generate the radius. But it presupposes that you could register the centre of the pivot point in some way. – Not getting my head around that part. – Though I believe I have seen a setting post method with an accurate half flat milled on, to index with slips or vernier. So with a mushroom head pin of a known dia. located on the jigs pivot centre it seems it could be possible to register the position by touching off on the flat? – Have a cutter grinder with X & Y calibration to facilitate the settings.

My head is hurting now. Any input appreciated

Martin – Could you elaborate a little please. Afraid I do not understand what you are telling me.