"Spike" wrote in message
...
On 07/11/2016 16:05, FranK Turner-Smith G3VKI wrote:

I remember the days of 'motorcycle tightness'. The procedure was to
tighten the first bolt until it sheared, then tighten the rest to a
quarter turn less.

Don't laugh...

A company had been contracted to build a spacecraft - it might have been
intended for Jupiter - and the structure was based on bolted-up elements.
Came the day for the first assembly, and as the special-material bolts
were tightened, they sheared. Puzzled, the engineers stopped the assembly
and checked the remaining bolts, their spec, their audit trail, etc, but
could find nothing wrong. Eventually they worked out that the small amount
of heating that resulted as they were being given the final torquing-up
was enough to reduce some material property to a level the bolt could not
sustain. They solved the problem by tightening the bolts in very small
increments and allowed plenty of time for thermal re-equilibration.

never try to undo bolts on a Koeran car ....