Hey guys im kinda new to this but so excuse me if this is a obvious or dumb question but i am wanting to make a rotary on the stock k40 board i know i have seen it done on here and read i would beed same size motor as my y axis stepper , i have looked but cant find a deffinate answer on the specs of that . Is there anyone that knows or knows the spec? Or where to look on my machine to find out which one my machine has ?
You’ll probably have to check the exact one in your machine. The Y-axis stepper is located at the front right of the cutting bay, underneath a metal cover (black in mine). Just undo the two bolts holding that cover in place & look beneath it & you should be able to get the part number from the particular stepper motor your machine has.
Ok i looked and found this number 42-2100c08s/sh tried google but came up empty any one kniw the specs
My steppers show model like this, on the drive shaft area. Note: both my steppers have different models.
Hmmm looked at both and that was the only number could i could find on either of the motors 
I also googled your model number but couldn’t come up with anything either. Hopefully someone else here has the same or knows the specs for it.