A thread roller would be nice. You can run a die over 2-56 or 4-40 rods you get from the hobby store, but nothing will fit them ! I found out the hard way. To get the right thread diameter for 4-40 it's best to start with an 1/8th inch rod and 5-40 die first, then go back over it with a 4-40. 2-56 would need similar treatment with the appropriate dies and rods of course-UNLESS you had a thread roller. Hmmm..wonder how much they cost ?