Originally Posted by SteveH

I am fairly sure the answer is the typical "it depends". If the gear is a transfer gear (in between two other gears and not under too much load it should work for a while but I would be REALLY worried about shavings and the like.

Funny you should ask because I was considering trying to make a gear copy for testing.

Brass or better yet Bronze, would be much better. I will be doing a reproduction next week using the clay/sand casting method and casting a bronze part. Photos will be posted here of course.