pulley fit on motor shaft - force it on?

This might be very basic, but I'll ask anyway.

What's the standard fit for a pulley on a shaft? got some pulleys from beltingonline and the one which fits on the motor shaft, which has a 5mm keyway and two grub screws looks like an tight fit, ie. I have to push down really hard on the pulley to get it on the shaft and even then it doesn't go all the way. I'm a bit reluctant to use more force as:

a) not sure what the shaft can take

b) not sure I'll be able to pull it off later

I think it gets a bit tight around the key, which seems pressed into the keyway on the shaft. Is it a good idea to grab some super fine sandpaper and run it around the sides of the key to take a tiny bit off and make fitting easier? if I'm talking crazy feel free to hit me.

Regards,
dsc.

It should be tight but not need twatting on with a hammer. Deburr the keyway and give the shaft a light rub with some wet & dry. It'll probably fit ok then.

Depending on the fit it has been machined to it might require a percussion adjuster. Colour in the shaft with a black marker, if you havent got any blue, then try to fit the pulley. Hopefully you will see where it is binding ie like the key is too high maybe. If its tight all round it might just be the fit. Whack the pulley in the oven for 10 minutes then drop it on.