Cutting down a steerer tube...

Can't imagine pipe cutters would be good on a threaded steerer, I would expect them to follow the groove, we've got a few around but I just use a hacksaw... cut straight and you're fine.

theyre only good for threadless, and youre right they follow the groove of the thread if you try on threaded (the partially sighted trainee mechanic tried it, it was rather amusing) "it doesnt feel like it's cutting! why isn't it cutting?"