Cottered Cranks - slightly loose - how to tighten up?

I"ve just obtained an old Raleigh 3sp and after a few days of riding around one of the Crank Arms has become slightly loose. you can just feel the movement as the crank arm swings over.

So how can I tighten them up? do I need to take it in somewhere with a Cotter Press? Can I just wack it in a bit with a hammer and tighten up the nut?

Do I need to remove it completely and File it smooth and stick it back in?

Whats going to be the easiest way to fix it up?

a hammer would be enough, just wack it, job done

You cannot get a cotter tight enough by tightening the nut, you must use a press or a hammer. Cotters are made of fairly soft steel, so that they won't damage the axle. If you try to tighten them just by turning the nut, either you won't get them tight enough, or you will strip the threads.
After a cottered crank has been re-assembled, the bicycle should be ridden for a few dozen miles, then the cotter re-tightened with a press or hammer. If this is not done, the cotter will probably loosen up. If the bicycle is ridden with loose cotters, the motion of the crank will cause the axle to cut notches into the cotters, and it will become impossible to tighten them.

read all here

whack them (not tappity tap- smack the fuckers) with a hammer and retighten. Or new ones are about £2 or something. Lock 7 will put new ones in for very little.

Tap out the loose cotter-pin. You will see a ridge where it has been moving. File the ridge out trying to keep the angle the same and the tapered surface flat. Re-fit tapping lightly with a hammer and tighten nut. Ride a bit re-tap and tighten. If still loose repeat the process. Whaking with a hammer will not work!

Life is too short to file cotter pins.
If a whack doesn't do it, replace them .

To file cotter-pin - about 5 minutes. Trip to the bike shop, about 20 miles or 1hour round trip and my local shop would not know what a cotter-pin is!

http://www.sjscycles.co.uk/product.asp?pf_id=22141