Metal finishing Q&As since 1989

-----

Hard Anodizing Iteratively

I'm considering the use of hard anodizing in aluminum parts for both hardness and hole size tolerance control. This will produce very small parts for internals to gasoline carburetors. Potentially, I'll want to control hole size to 0.00004". I had supposed I could do this in an iterative process: coat, rinse, check, recoat until the proper size is achieved. Some discussions I've seen on here seem to indicate that is a not feasible, but that I would have to strip and start over each time. Any help?

Clint Patrick

Marshall Clinton Patrick
Machining: custom/hobbyist - Athens, Alabama
2006

---

2006

Wow, that's quite a tolerance you are trying to hold there. As a hobbyist, do you have access to the type of equipment it takes to measure to the hundred-thousandths of an inch? Most CMMs in machine shops are only good to the ten-thousandths of an inch, and even then, there is always a ± error rate. You could attempt to use anodizing, just start off with a short time, and then check frequently until you have the desired size (obviously you'll need your measuring pins/equip right next to the anodizing process.) But once you get too small, you'll be stuck with the aforementioned option of stripping, and starting again.
Tight process control in the anodizing process, and machining process, will be a must for a repeatable result.

Marc Green
anodizer - Boise, Idaho