On Wed, 11 Nov 2009 23:13:37 +0000, Roger Mills wrote:

Does it really need to be as accurate as your specification, if it only
rotates slowly?

Probably not. The measurements were just those obtained from the existing
shaft. I didn't want to round anything off in case it resulted in it
either not fitting, or being too loose for good grip (there is no grub
screw arrangement in the flapper end - it just sits inside a D-shaped
channel through its centre).

Does anything have to slide along the D-shaped shaft in
operation, or only in assembly. If the latter, can't you: * Start with a
length of 8mm mild steel rod * Rotate it in a drill chuck, and use a
file and emery cloth to reduce it to 7.6mm

Hmmm... interesting. Do you think that would work? I haven't got a pillar
drill - or were you just talking about a suitably-clamped standard drill?

* File the flat all the way along
* Bore out one end of the coupling - thus avoiding having to reduce the
end of the shaft to 6mm?

I hadn't considered boring out the coupling either! I suppose though if I
can form the rest of the shaft with my 'homemade lathe' as per your
method above then I can just go a bit further with the small end..?

Mathew