"Well if your using a pipe cutter designed for alloy tubing in what way are you using the wrong tool? "
because pipe-cutters are very good at cutting, er, pipes which are usually made of very thin and ductile materials as opposed to steerers which are on the whole thick and hardened, tending to wreck a pipe-cutters blade, and as mentioned they leave a ridge that needs to be filed away before you can get the stem over
and let's not even think about the terminal damage a pipe-cutter can do to a carbon-steerer
in the OPs case it makes sense, as he has none of the tools, for him to get the right tools straight away rather than blunder into the usual STW bodge, and as mentioned, a hacksaw is quite a useful tool for other jobs
a cutting-guide for steerers (and handebars and even seatposts should you wish) is one of the best tools i've ever bought, it makes a potentially faffy and error-heavy job into a quick and easy affair, and the tool can be lent to friends in return for beer, it's paid for itself many times over in ease, efficiency and alcohol