Originally Posted by
franz
In reality it is not a difficult job,you just have to pay attention,when you drill the hole, not to puncture the passage of the air below: to do this you need to take a drill with a stopper, so as to allow the drill bit to drill only the stainless steel wall of the piston. I made the hole of the same diameter as the one on the bottom of the piston, i.e 3mm.
I don't use a drill stopper/collar for this -- a bit afraid of marring the surface of the piston, and I do have a lot of experience in drilling thin sheet metal. If you've done this sort of thing before, you can feel when the drill goes through the the piston wall. Of course, I use a drill press. Using a hand drill, it's a bit more difficult to have the necessary control and sensitivity to not go too far, difficult to avoid the bit "skipping"/sliding on an unpunched curved surface (and you sure don't want to center-punch that piston wall!), and a lot easier to slip and ruin your piston.
3mm strikes me as an excessively large hole for a piston vent, at least on a euphonium (almost twice as large a diameter as is common). In general a much smaller hole is drilled -- more on the order of 1/16" (1.6 mm) or 5/64" (2 mm). If the 3mm works for you, then it works for you. But people should keep in mind that the point of the piston vent in the sidewall is to vent AIR while the point of the vent in the bottom of the piston is in part to allow accumulated water to drain out, and it also has to vent MORE air in less time than the wall vent does. Too large a vent hole could result in giving you some really airy slurs. Just beware of going a little far with this.
Gary Merrill
Wessex EEb Bass tuba (DW 3XL or 2XL)
Mack Brass Compensating Euph (DE N106, Euph J, J9 euph)
Amati Oval Euph (DE 104, Euph J, J6 euph)
1924 Buescher 3-valve Eb tuba (with std US receiver), Kelly 25
Schiller American Heritage 7B clone bass trombone (DE LB K/K10/112/14 Lexan, Brass Ark MV50R)
1947 Olds "Standard" trombone (Olds #3)