Some bike shops have a cotter press (in the old days they all did). You can buy one for about $60.
If you have a stout C clamp and a socket, you try to squeez it out (the socket goes in between the crank and the clamp so the cotter has somewhere to go). Once you've applied all the squeeze you can with the clamp, you tap it (the clamp) with a hammer and it (they cotter) will usually pop out.
You can also cut a piece of pipe to just the right length to reach from the floor to the crank and pound the cotter down into that.
You can just tap it with a hammer but if you tap too hard without backing of some sort you will damage the bearing races.
If you're still fighting it, go to bed. next evening when you're not shaking mad at it, drill it out. Remember, it's flat on the side that faces the spindle so aim a little off center with the drill.
Read this too; http://sheldonbrown.com/cotters.html
Last edited by sailorbenjamin; 11-08-09 at 08:36 PM.
Reason: that's what I tried to copy 3 times.
I'm pretty sure your bike is a Raleigh, made in Nottingham. By 1965 Raleigh was manufacturing all the bicycles sold under the names of a large number of companies that had previously been independent bicycle manufacturers in England. The same bikes were also sold with the names of American brands. I don't know which of these Armstrong was, but one way or another, what you have is basically a Raleigh Sports. And very nice, too.
Thanks I do apperciate the information that has been given. I am currently restoring it slowly as time allows. The paint job on it really stinks (old age and original). To some it is the money they can get out of it, to me it is really cool to restore a piece of history older then I am.