hi every1...i am designing my own cnc machine...i am working on stepper motor....my stepper motor has 1.8 deg step angle in full step mode means 200 steps per revolution in full step mode and 400 steps per revolution in half step mode....i am working on half step mode.
now i have derived the stepper motor now i want to convert this circular motion into linear...for this i wanna use rack and pinion....but i dont know what type of rack and pinion should i use ....what should be the specifications of rack and pinion so that my stepper motor would perfectly run with that rack and pinion????

please help me out what parameters should i consider for chosing rack and pinion for my motor????

please explain me in detail...