That is assuming that the current listed is Peak and not RMS/phase amps. Which is what I really want to know is which is it. Not the assumption of use it as Peak and therefore add to the safety margin of the motors operating life span. IF it is phase/RMS then using 4.2 as peak reduces the current that motor can use to .707 of what RMS would be.

Let me write it this way:

Which is the 4.2A on said motor? Peak or Phase? Why?

Peak is 1.414 * RMS (or put list the inverse RMS = Peak * .707)

IF it is Peak then fine set accordingly and everything should run fine.

IF RMS then either set as RMS (IF Driver lists RMS Amps) or do the math to arrive at what peak current you can use for said RMS.

IF set as Peak and IS RMS/Phase then you have a problem RMS/phase being .707 of Peak means that you take 4.2 * .707 = 2.9694A is your operating Amperage (RMS/Phase) IF that was peak; this section we are assuming RMS so you have reduced you usable power by 30%.

Now for folks coming into this discussion and not having a clue why it is important:

RMS/Phase is the current you stepper motors run at under normal full current load (no micro-stepping no stand by mode).

Peak is the max that the motor can handle without damage to the motor from use under these conditions (normally for sustained periods).

While you can use RMS as peak it decreases the effectiveness of the motor as well as it's torque.

This is why I am chasing this information down to find out which it is so I can set up the best option on my machine for power usage.

Michael