hi, i have a kona caldera with an fsa alpha drive chainset which im changing, now im using a park tool crank arm remover but the bit that pushes inwards is too small and ends up pushing straight through the hoollw bit that runs through to the other peddle arm, i tried putting a coin there to push more against the outer but it just whole punches the coin. i know its not very well explained but can somebody please help me? thanks

Use a small socket piece instead of the coin.

find something stronger than a coin?
some tools come with a little plate that fits on the end, have you lost it or is it too small?

Try several coins.

bike shob will have a little adapter available or maybe find a bolt which will be stronger than the coin. isnt it against the law to deface a coin?

there's a top hat shaped item, that should have come with the tool, which you need to make it fit properly. some people claim that a 5p bit will do it, but as you've found out, that ain't neccessarily so.

if it is im buggered. but yeah the little plate at the end of it is too small, im assuming there are larger ones out there but the one at the moment is just sliding straight through

screw in the retaining bolt the minimum amount possible so that thread is available for your extracting tool.
screw in estracting tool
slowly extract crank arm.

this worked for me with a shimano 105
you may need to put a bit of locktite on the thread where the retaining bolt goes (on the BB) so that when you turn the extracting tool it doesn't screw the retaining bolt in any further

I use a pan head screw!