They are technically called roll cutters, or specifically "displacement cutters" and for a reason. When they "cut", the wheel just "smooshes" the material out of the way until it breaks in two leaving a flaired mushroom end on the outside and a huge burr on the inside. Much filing/reaming inside and out required for a close tolerance stem insertion. Really is meant for actual gas pipe, not chromo or high end light weight high strength steel.
I see I was typing way too slow, Joe.
