Posted by Rick Denney on February 08, 2004 at 14:52:13:
In Reply to: Re: venting posted by pistons? on February 08, 2004 at 11:13:36:
It's easy to vent pistons (easier than rotaries, actually, because there is less disassembly and cleanup involved--the work is done on the valve rather than the casing). As Gus says, you make a hole between the port going into the unused valve branch, so that it vents through the hollow valve out the drain hole at the bottom of the piston.
Once a techniciean sets up to drill one valve, it's a piece of cake to drill the other three. Matt Walters cut the vents on the York Master, and the cost for all for was under $50. The cost for just one was two-thirds of the cost of all four.
You can do it yourself, but only if you have really good hand skills and are willing to take meticulous care. A mistake raises the cost of repair ten-fold, whether it is drilling too far or accidentally chewing the piston up under the drill press (or launching it across the room). The proper bit speed for such a job is about 100 rpms, and I'd be strongly tempted to drill it by hand using a bit in a pin vise (that was how I drilled the vent hole on the first valve casing of my Miraphone, too), or using a lathe to mill the hole in a piston that is clamped (properly and carefully) to the tailstock.
I vented the pistons on my Yamaha F tuba by using a Dremel cut-off wheel and making a small slot at the right place on the piston. The slot ran vertically along the valve, and was just big enough to make a vent hole. That seemed easier for me to control than a drill, especially a power drill. It's an unconventional approach, but it worked.
I haven't needed to vent the pistons on the Holton, because I don't move the slides when playing and because I can use the water key to vent slides when I pull them to empty water. Those were both issues on the York Master (and on the Yamaha). I won't vent the slides on the B&S, because I don't think in normal playing I'll be needing to move slides, and that instrument doesn't hold water anywhere except the main tuning slide.
Rick "who vents slides to solve a problem" Denney