Plastic gears 101: Leaving behind a metals mindset can help turn your plastic gear set around.

So you need a plastic gear set. Just crack open a catalog or design handbook. With a little basic information about center distances, pitch and pressure angles in hand, you pick some matching gears. And presto, your new gear set is ready to roll.

Or is it? Plastic gear experts blame this kind of sketchy, yet common, design practice for many of the failures that in the past gave plastic gears a black eye. "There are a lot more factors to take into account with plastics than with metals," says David Sheridan, who works on plastic gear applications as a senior design engin