On Sun, 27 May 2007 21:23:55 +0100, "Davy"
wrote:

"Ian" wrote in message
.. .
On Sat, 26 May 2007 20:00:39 +0100, "Davy"
wrote:

Regarding which is the correct bolt to draw the disc off the crank;
Looking end on at the head with a flat horizontal there are three
lines one pointing to the top flat (12 o'clock), and the other 2 at
120 degree intervals (i.e pointing to about 4 and 8 o'clock). Does
this help identify it
yes, this is a 'unified screw' bolt; the bolts have three equally-spaced
radial markings, the nuts would have three circles. The bolts should also
have a figure at the 6 o'clock position which denotes the grade of steel and
hence the maximum tightening torque; if this is missing then the bolt is
low-grade steel. In which case the maximum torque that should be applied to
the bolt is below 65 ft/lb - more than this and you risk damaging the thread
or shearing off the head.
The closest match to your description is a 7/16 UNF bolt which has 20 tpi.
It will not fit a 7/16th BSW thread so my supposition about BSW being used
was wrong. But you state that your machine is metric so we would expect a
metric thread; a 7/16th diameter bolt equates to 11mm. The nearest common
metric sizes are M10 (17tpi) or M12 (14.5 tpi) - so no metric equivalent of
this size. Perhapsy Hayter changed the fastenings to metric by 89/90 but
not the components?

I look forward to hearing whether your old machine has the same arrangement
since it is much closer in age to my 1968 machine.

Many thanks, Davy


Davy
Sorry for prolonged delay in replying - I only remembered today that I
hadn't replied.
My old machine has exactly the same arrangement. I don't think I have
ever had the cutter disc off before - if I have it is many years ago,
and the last several the m/c has stood outside (shame on me , I know)
- retaining bolt came off with little effort. My 'puller' HAS drawn
the disc along the shaft but not far enough to actually remove it.
Need a longer 'puller' bolt or a hammer!
HTH
Please reply to group - email address is not monitored
Ian