Posted by Rick Denney on July 08, 2003 at 17:40:17:
In Reply to: vented valves? posted by Mike on July 08, 2003 at 17:13:14:
A vent on a rotary valve is a small hole in the casing between the two tubes that form the valve branch. I think I see one on the fifth valve of the tuba pictured, but I have never seen one that I would call a "threaded insert." Perhaps someone had the valve vented, regretted it, and threaded the hole for a small screw that was then filed to shape on the inside of the rotor casing.
Rick "who vented the first valve on his Miraphone" Denney