I have a domestic paper guillotine (BABS Premier 14) that I want to
fix to a wooden shelf. There is a flange each side with a hole on each
corner. Previously, I just used M6 bolts and nuts through the holes
and the shelf, but now I want to hang drawers underneath the shelf and
the bolts/nuts would get in the way.

Hence my idea of using spire nuts like the ones used extensively in
the auto industry. I'd drive Posidrive screws from underneath the
shelf into the spire nuts. If the screw heads were countersunk, they
would not get in the way of the drawers at all.

But thinking back to my days as a motor fitter, these spire nuts were
intended for *body panel* steel, which isn't very thick. The steel
flanges on the guillotine are 2.5mm thick. Is that too thick for a
spire nut?

MM