The new design that I am using for square/rectangular tripod leg casters has a number of advantages compared to what I was doing before. Instead of making an adapter to convert from caster to tripod leg out of a single piece of acetal, I now use an aluminum tube and a piece of acetal that I thread for the caster. This has a number of advantages:
1. Much faster manufacture time. The aluminum tube already has a hole in it!
2. If you machine a single piece of acetal, and somewhere along the way, you screw up, you now have an unusable piece of material. I made a mistake yesterday while making a set for a new Losmandy tripod--I drilled the locking screw hole on the wrong side. No problem: I only had to replace the tube part, not the acetal that is drilled and tapped for the casters. And the part that I have to throw away, at least, can be recycled, because it is aluminum.
3. When I start to make the technology switch for the round tripod legs, the same two part strategy means that I can make lots and lots of identical adapters of acetal to fit into one end of round aluminum tubing--while I can machine the other end specific to particular tripod legs. The more you can mass produce at least one part of your product, the cheaper that part gets. I've never seriously considered having these gadgets stamped, cast, or injection molding because you have to have so many of them made at once to be cost effective. But perhaps the threaded acetal adapter--this will be made in sufficient quantity to consider it.