HF blades work in Martelli cutters, but you have to unscrew the screw once in a while or it will get too tight. I think Martelli designed the cutter with the screw BACKWARDS so this would happen, and we'd think we couldn't use any blades but theirs!
Look at the cutter, and you'll see they put arrows showing which way to to turn it to change the blade. Anyway, if you let it get too tight, you'll need 2 wrenches to loosen it - one to hold the blade and one to turn the screw! The Martelli blades have a notch that keep them from getting too tight. Sneaky, heh!