Gear Media

Question:

I have heard the term, “gear media” and I wonder what this is. We debur fine tooth drive gears for electric hand tools, and have always hoped for a media to “pick” between the teeth. Please tell me about this media, or any other that might get into the 1/32-inch space between the gear teeth. J.U.

Answer:

As far as I know, the originator of that term was Sam Thompson, a sagacious, and now retired, vibratory finishing expert. Sam is well known in the New England States. I have lost track of Sam, but often think of him, and his interesting stories, and his sound advice. (If you read this, Sam, give me a call.) The media that got this moniker from Sam was a 3/8- x 3/8- x 5/8-inch 60 degree angle cut ceramic triangle. It is usually made from a fast cutting composition to make up for its low mass and delicate contact. If you can picture, or draw this shape, you will see a very long sharp point at each end. The edges leading to the point are slivers that can get into lots of small areas not normally available to ceramic media. Sam had good experience with this product, and I know at least one manufacturer that still produces it. Will it work for you? I don’t know, but getting a sample run should answer the question.

Another media to consider for your gears will be metallic media. This is available in small pin shapes, and little pointy “football” shapes. You might consider using carpet tacks, finishing nails, or brass brads. Be aware that small media can plug the drain holes in some machines. Metallic media may introduce corrosion control problems you did not have before. Talk to your compound supplier about this before loading a machine with any metallic media.

I had a bad experience with “gear media” that I will share with you. I made the mistake of recommending it for gears that weigh about a third of a pound, and that had teeth just far enough apart for the pointed ends of the media get stuck—not really lodged, just stuck. Then, while the parts were being tumbled, the media would break in two, leaving many tips in the gear roots—that was really lodged, not just stuck!