# Thread: Pinion / Gear / Gearbox calculator for stepper motor

1. ## Pinion / Gear / Gearbox calculator for stepper motor

Hi,

I have a small problem which I am trying to solve.
I need to calculate the size of a small pinion to drive a much larger gear wheel. These are all based on a Mod 1 type teeth. I would like to drive the pinion with a geared stepper motor so need to include the gearbox ratio.

The pinion size can be chosen, so for example from 12 to 40 teeth. The large gear is fixed with 636 teeth.

I would like some sort of explanation of the calculation or even a spread sheet listing the 12 to 40 pinion options but where I can enter the stepper gearbox ratio, such as 30 for a 30:1 gearbox.

I need to choose an the gearbox / pinion to give me 0.5 Deg rotation on the large gear with only one step of the stepper motor., which will be a standard 1.8 Deg/Step (200 Steps / rev) motor with and attached gearbox.

I have made a spread sheet to enter the gearbox ratio and it lists the steps required for 0.5 Deg for all pinion sizes, but I am not convinced it is correct. I will then choose a pinon / Gearbox combination that gives a full step per 0.5 Deg. Such a 165 steps for 0.5 Deg, or 212 steps per 0.5 Deg etc.

Any ideas? Or maybe seem could point me in the right direction for an online calculator.

Thank you for your help
John

2. This is a simple ratio calculation:

1.8 deg step-deg / 0.5 step-deg. = 1.8: 0.5 gear ratio. or 3.6:1

Use this tool with standard gears to develop your gear train.

https://www.engineersedge.com/gearanimator/index.htm

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