Peter Ashby wrote:

If you do, a post of the valve would be appreciated. Some of the dog
holes in my bench are necessarily blind and so need vacuuming out on
occasion which might cause the problem you see.

How about using one of the small door catches which have
two spring loaded ball bearings pressing into the sides
of the catch plate. The better ones of these are
adjustable for tension.
atmosphere
_____________________ ______________
_____________________| |_______________
hinge O_||____________||____ ||
vacuum side |_____________________|== catch
||


I suppose it wouldn't be self resetting though.


Nick