This old house has lots of old door knobs, but some are a bit worse for wear. I've already repaired a broken spring in one with some cobbled together bits from an old wooden clothes peg, but that's another story. Another was lacking a crucial grub screw that meant the knob on one side just rotated freely, rather than operating the latch. The nice guy at Alban Locksmiths furnished me with an Imperial threaded screw that fits. However I needed a grub screw – one where there is no 'head' so to speak so that it can worm its way right into the hole.

No problem! Just saw the head off the normal screw then saw a notch in the end for the screwdriver. Here's a pictorial essay of my approach, the only trick of any merit being to clamp the screw between two bits of soft wood in the vice, so that it's gripped securely and you can saw it without it slipping or being damaged.