Ok Jonno, hard to photo properly, but this shows the idea.
Left, Spring loaded centre pin and mini hole as cutting blades - Hard to use as centre pin is not strong enough to hold it steady.
Next, P&N spot weld drill bit - Great to use, works well
Next 3, home made verisions of the P&N , work very well, have done many welds and been re-sharpened a few times. Different sizes to allow for weld size variations/penetration/doubling.
Made with bench grinder to get almost, but not quite, flat end, with a 2mm tip in the centre. Then a 1.5mm thick angle grinder cutting blade to put cutting edges on the centre tip.
Much easier to drill through only one skin, re-assembly is quicker and easier than drilling all the way through with a normal drill bit.
L serious, still.
They do come in handy with the 1/2" drive on it, I would have thought these days most people would just use an air impact driver though.
This brush will be cleaned and used to scrub the acid before it get's a sealing coat of red oxide paint.
