I've stripped my Raleigh Twenty down, and removed most of the paint, but I've had to work round the cranks. As far as I'm aware with cottered cranks, you undo the bolt then give the pin a firm tap with a hammer - am I misinformed? The pins don't move and if I hit them any harder I'm going to risk damaging the thread. It's an inconvienience more than anything (I can tape up for the respray and at the moment the BB is running nicely). Any tips?

Don't mess with old cottered cranks unless you really have to.

Getting them off is tricky, and as you noted, if you ruin them you will never get them off without drilling them out - and that is a task for a machinist.

I always used to soak them in penetrating oil, undo the nut and protect the thread with a block of wood.

You could also try loosening the nut and riding the bike for a bit. It's obvious as soon as they come loose, but stop right away.

A GOOD LBS will have the proper tool to remove those pins.

Barring that, back the nut off a couple threads, hold a flat bar, or something, on top of the nut and hit it with a 3lb hand sledge. When it moves, back the threads off a few more turns. Hit it again.

Another method is using a very strong C clamp --not a light 2 or 3" clamp. but a 5 or 6" one that is heavy and strong. Loosen the nut and then place a short strong hollow tube over the pin, on the opposite side of the nut, then tighten the clamp. This simulates the special tool the LBS should have.

BTW, those pins shouldn't cost more than a dollar if you have to replace them. There are several sizes, so take the old one with you if replacement should become necessary.

Don't be intimidated! It is not a difficult job. And I, personally, consider it absolutely essential to grease the BB when over hauling a bike. Once it is apart, you can decide if you want to upgrade it to the more common square taper cranks.

Consider replacing the crankset with cotterless upon reassembly. I hate cottered cranks ...

When pounding out a pin, make sure you support the crank itself, to avoid transferring the impact to the bearing surfaces.

Thanks - I think for the time being I'll keep them on and paint the frame round them. If/when the BB goes I'm probably going to have to go for a Phil Woods special and I can replace the cranks then. At the moment the BB is fine, and I've got the original heron design chain wheel.