id show pics of my shot at doing that with spirals, but i cant cut very straight with them either. however, i do use them for portrait work. in this one, there are some cuts that(3 in particular), if laid out in a straight line, are quite long and jagged. using a straight blade, i would have had to swing this piece every which way to complete the cuts. with a sprial, no need to swing it all over- just move the piece left to right,front to back or whatever direction necessary without having to spin it.