"The Natural Philosopher" wrote in message
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Now I am fairly sure that around 1990 or so, Hayterettes did NOT have
this arrangement..mine is 1995 but I never took the disc of myself yet.

So I might tale the disc bolt out and see what is there

Dear Phil'

If your Hayterette was made about 1990 then it may well be metric. My
hayterette and B&S engine was made in 1968 so might be different still. In
my rambling discussion about bolt size, because all of the dimensions that
Ian gave were imperial, I had not considered that Ian's machine might be
recent and hence metric.

Let me know what happens if you have a go at getting the disk off. I am
losing the courage to take off the blade disc retaining bolt since if the
head shears off leaving the bolt thread in the end of the crank then my old
machine would probably be scrap!

best wishes, Davy