Hi All, replacement of said screw is necessary as years of blunt screwdrivers/nail files/ butter knives have destroyed the slotted head.I read that it is 12BA-got some- nope, falls in, too narrow on diameter.Next size available: 10BA-too big won`t go near. I read elsewhwere its metric,....logical: 1.4mm,-got some-screws in but hoplessly loose & wobbly. Hmm, the annoying thing is that the original, knackered screw is a darn good fit in the trip shaft with no play at all, and close examination gives a dia of 0.055" and .30mm pitch-which appears to be as near as dammit 11BA-a size which seems to be unobtainable as suppliers lists go 12BA-10BA,( well they would would`nt they?) Anybody any ideas as to a supplier of 11BA?, or is it another size (1.6mm has a 0.35 pitch-doubtful it will fit....) Ideas appreciated, cheers, Bob.