Cutting/Trimming tubing

[Tubajug]

I would like to trim down the 3rd valve tubing on my "new" Bach tuba to try and alleviate the horrible flatness thereof. With the first valve tuning slide on top, I would be able to manipulate 1-3 and 1-2-3 combinations and hopefully still come close with 2-3 (which right now is just nasty flat).

Is there any trick or tool to use other than a dremel-type tool and a tuner to check as you go? Anyone know the approximate amount of tubing to trim to get these tubas better in tune?

[PMeuph]

I cut the 3rd slide on my 12J before selling the horn. I removed about 1/2" from each leg of the slide (1" total) that improved the tuning and brought it up about 20 cents or so. I used a good old hacksaw and some sand paper to clean up. I put several cotton balls down each slide to make sure I would catch most of the dust from cutting.

If your Bach is like the Conn/Olds horns, and even if you do cut too much off, the slide inners are probably still long enough for you to play with the slide out more than usual and still be in tune. You might need to move a brace or two...

[aqualung]

Get yourself a tuba-playing friend with a similar horn that has the 2-3 combo the way you want it. Tune the horns together on an open note. Then play the 2-3 notes together. The amount your partner has to draw his slide to match you is the amount you have to trim.

Clean up your cuts and insert the inner slides, one side at a time. The amount they each protrude when fully pushed in is the amount you need to trim.

Cutting tubing ON the horn is tricky. Patience is a strong asset. Use a wide-bodied fine tooth blade, it tracks straighter than a jeweler's saw. The toughest stage is when you are getting ½ way through, and the saw kerfs hang up because the thin metal is perpendicular to the blade. Patience is a strong asset.

Cutting tubing off the horn gives you more options. A small table saw works best. I also have been using a neato mini chop saw from Harbor Freight, but dealing with tuba-sized tubing is beyond the design capacity of the saw, and requires jumping through some hoops. You can also use a hand saw, and hold the tubing in a V-block.

A cutoff disk on a Dremel also works, but be prepared to break a few. You'll need a very steady hand to make a true cut. And shield the components in the line of fire from the oopsies.

Did I mention patience is a strong asset while doing any of this?

[Art Hovey]

To figure out how much needs to be removed, use a tuner to measure how flat the instrument is with that valve combination in use. Then pull the offending slide until it is twice as flat. That's how much you need to cut off.

If it's a BBb tuba similar to an Olds or Conn 12J then you need to cut about an inch and a quarter off each side of the 3rd valve tubing. Use a new hacksaw blade with the finest teeth that you can find, holding it to cut on the pull stroke rather than the push. Put a layer of masking tape around the area being cut, and also several layers on any parts of the instrument that your blade might hit by accident. (Also wrap something around the saw blade where you hold it to protect your hand.) When you get near the middle of the cut try for quick, light strokes.

When you finish the cut, use a file to smooth and square off the cut end. Go around the inside edge of the cut end with a sharp knife to trim off the burr.

If you have not done this before it's a good idea to practice on a junk instrument first. The job requires some patience, but it's not brain surgery. Even a ham-fisted shade-tree tuba mechanic like me can do it.

[MartyNeilan]

There is a spacer tube inserted in the long side of the #3 slide. If you simply chop of the bottoms of the outside slide tubes (without addressing the spacer tube situation) you'll end up with with a stubby little #3 tuning slide.

What are your recommendations on removing that inner spacer? Is it soldered or just pressed in?

[tbn.al]

I must admit I got bored with the auto transmission video and stopped it before completion. Did I miss the part about the inner sleeve?