Jerry, I can't argue with what works best for you, but I can say that I've seen several machines that manufacture items from small diameter wire or tubing that use straighteners that are made on the same principle as the one that I made.

I would say that it would depend a lot on the alloy of the material and it's propensity for work hardening. Now the 4130 you spoke of might not be a good use for a tool like this due to it's carbon content, but most material sold for use as brake lines is a lot more ductile than 4130.