Before you model a gear, go to
www.3DContentCentral.com. I used to use Boston Gear when I was a designer, but there are many manufacturers. You need to specify parameters such a pitch, diameter, number of teeth.
You will get a simplified version of the gear, with our without a keyway.
Although this does not contain the exact curve, they are close enough for a purchased part. When given the chance - get the model from a supplier, don't waste time creating the model. Marie