a thought; if you are stuck for such a key, could you grind a hexagonal one to fit?
I think the best tool for doing this would be an angle grinder (rather than a bench grinder) because it will cut faster and make less heat in the work.
To make it as easy as possible, good marking out is essential. There are some tricks here, e.g. I'd suggest that;
- you could print out on paper a pentagon in the correct size and stick that to the work, which give you a guide to work to. A permanent mark can be made for each face using (say) a cutting disc on a dremel tool.
- or you could simply use a blob of blu-tack (or plasticene) on the end of the key, and take an impression of the socket directly. Trim off the excess with a craft knife. Again a dremel tool could be used to make a mark for each face.
- when grinding the key up, I'd suggest that to start with you grind the key with a slight taper to it; once the nose of the key enters the socket, you can determine which faces are touching and which are not. These faces should be ground a little more than the others when you start to grind the key faces parallel.
It probably takes longer to describe than to do the job!
cheers
