Since I began making reels in 2011, I have been using a vibratory tumbler to finish parts. This is effective for aluminum and brass reel parts when used with”plastic pyramids” media. A typical part would get 4 hours of vibration, and then would have a dull finish which was easily brightened by manual work with fine grit wet sandpaper. The main function of tumbling is to uniformly remove sharp corners left on the machined parts.
About a year ago, Reelmaker Anders bought a rotary tumbler and told me that it was an improvement over vibratory tumbling. Rotary tumblers are used by ammunition reloaders and jewelry makers. They differ from rotary rock tumblers in that they run at higher speed and use stainless steel media.
So I have recently bought a rotary tumbler, the “Platinum Series” by Frankford Arsenal.
The barrel is big; it has a 4 inch diameter opening at each end and a volume of 1.5 gallons. It also has a built-in timer. Tumbling is done wet; you nearly fill the barrel with water.
This tumbler is marketed to ammunition reloaders and comes with 5 pounds of media which are stainless pins of .040 inch diameter and 0.27 inch length. I felt that this was not the right thing for reel parts, so I have substituted a “jewelry mix” of 5/32″ balls, 5/32″ ball-cones, and 1/8″ diagonals.
I have been running parts 2 hours and getting the same sharp edge relief that I got from vibration. Further, the parts are bright right out of the tumbler and I can run more parts at one time.
Update 23 Dec 2020: The stainless media is good for bronze and steel parts, but not so for aluminum. It is a matter of density: Solid aluminum 0.10 lbm/in^3, solid bronze 0.27, solid steel 0.28, stainless media 0.18, plastic pyramids 0.03. An aluminum reel spool will “float” on top of the stainless media and not get well polished. It gets worse as you add more water to the mix because that makes the aluminum part even more buoyant. So for aluminum I am using a product from Surf Tumbling Media. It is “Green Plastic Tumbling Media General Purpose – Deburring Pyramid Shape – 1/4 inch”. My tumbling barrel is sufficiently filled with a 2.5 pound bag. Leaves a nice matte finish so the anodized spool is not reflective.