One of my colleagues at work asked me if I could turn him some motorcycle engine valves on my Boxford. I said it was unlikely as the material was hard (he said he had a friend who could get him some square section) and from the finish I've seen on car ones they look precision ground. Any other thoughts on this?
Bill H Derby
VERY many years ago (I was still at school and used the school workshop so before 1966!) I turned down the heads of some motorcycle valves for a friend. He had sourced valve for a different bike with the same length and stem but oversized heads, which I turned down using brazed carbide tooling to fit his Panther 650 sloper. I don't recall it being too difficult
AWEM
I use inconel exhaust valves as blanks, taking small cuts is quite easy with new sharp carbide, but I don't know how that would compare with whatever square section the chap can get.
The very top bits are hard - made of stellite - and the shafts can be hard chrome plated, but otherwise a valve isn't that hard to turn with carbide tools.
The valve shaft probably is precision ground though - the head can be ground into exact shape in the socket, so precise accuracy there is probably not essential, but getting the shaft right on a lathe might be a bit tricky.
Another potential problem I can see is going from square to round, carbide doesn't like that sort of interrupted cut, and you may have to use HSS and sharpen it a lot.
-- Peter Fairbrother
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