They are nema 17's. However what you don't have on your cnc is a hot end or a heated bed. Which both use normally 12v modules to keep the cables at a reasonable level. It also stands to reason the same amount of work done at 12V @ 10amps you need 24AMPS from a 5V psu while increasing the cable size dramatically. Lets say the heated bed needs 100W to operate, at 5V it needs 20AMPS, while all fine and dandy, however the cable size becomes a larger issue, now you need a 5 Gauge cable, vs at 12v you need a much thinner 12 gauge cable. Assuming 1M length. ~3feet

Your argument may be so what? Let me tell you that most of these printers need at least one cable that is constantly flexing while being moved, and it add load to the machine if your moving battery jumper cable sized wires. That's 5mm cable vs a 16mm cable..... I am generalizing here as there are other factors in cable sizing, however higher voltage is a nice thing in these things, also most of the accessorizes are designed to run on 12v.

I Put this together as no one in the community bothers talking about power requirements, yes I went overboard on my power domain, and yes it may cost a bit more than the ps3 power brick. The fact of the matter is that I got my server spec psu for absolutely nill, and my needs were for 12V power.