Vintage Bach 9 factory mods?

[Rusty]

I came across a Bach Corp 9 with ‘F’ marked on the throat and ‘413’ marked on the shank. What would these mean?

[Rusty]

Another example. Wondering how these differ from stock specs?

[Matt K]

That's the backbore number:
https://bachloyalist.com/bach-mouthpiec ... ne-models/

[JohnL]

The letter is the drill size for the throat.

G = .261" (6.63 mm)
F = .257" (6.53 mm)

For frame of reference, the Bach mouthpiece manual lists the "standard" throat for most small shank mouthpieces as .230" (5.85 mm). The G drill is the standard throat for the small shank 6½AL and 5GS (those sizes also list a #420 backbore). The small shank 6½AM is listed as having an F throat and a #413 backbore.

It's not specifically stated, but I think the standard backbore for small shank Bachs is a #402.

Note that the backbore designations are reamer numbers. A larger number indicates a larger backbore, but the numbers don't seem to indicate any specific dimension.

Opening up mouthpieces wasn't uncommon back in the days when there were fewer choices. Most of the time, they just drilled out the throat.

[Thrawn22]

I was wondering the same thing about a 7 i have stamped woth a B on the shank

[Posaunus]

I was wondering the same thing about a 7 i have stamped woth a B on the shank

B drill size: 0.238" (6.05mm)
Standard Throat for a Bach 7C is 0.230" (5.85mm)

[GabrielRice]

It's been my understanding that Vincent Bach's strategy - for trumpets and trombones - was for the standard throat to be on the small side so that a "stronger" player could have it opened up.

[chouston3]

If I wanted to open up a mouthpiece, are there some best practices to follow?

[BGuttman]

If I wanted to do open up a mouthpiece, are there some best practices to follow?

1. Be prepared to create a bunch of paperweights from your experiments that don't work out.

2. If you insist on this plan, remember to round out the sharp edges at the beginning and end of your drilled hole. How much rounding? That was the kind of knowledge that kept "Peppy" in business.

[GabrielRice]

If I wanted to open up a mouthpiece, are there some best practices to follow?

Don't do it yourself. There are many custom mouthpiece makers or good brass shops that can work with you. If you tell us where you live, I'm sure you can get many recommendations.

[elmsandr]

Contrarian point: do it. Figure it out. I have a Schilke that I opened up a bit in college. Don’t do this with an expensive mouthpiece, do it with a commodity level one. Make small changes. Smooth things out, figure it out with pencils wrapped with sandpaper/emory cloth. Do NOT however, expect this experiment to really work. The Schilke I mentioned above… went too far. Learned a lot about what not to do again.

Makes a great piece to buzz on now in the car. Plays poorly in a horn, wish I had stopped about two tweaks earlier.

As Gabe notes, there are people that are good at this, buy something from them if you want it to really work. If you want to experiment with how this works, it is fun and you will learn from your mistakes.

Cheers,
Andy

[Thrawn22]

I was wondering the same thing about a 7 i have stamped woth a B on the shank

B drill size: 0.238" (6.05mm)
Standard Throat for a Bach 7C is 0.230" (5.85mm)

It's a non C 7 mpc. But thanks! I now know:)