TromboneChat

Hi mates,

I've recently got a MT Vernon Bach 42B and exploring the slide, it has 13,75mm bore. Its not 13,89mm.

Any of you has a slide like this and could see if it has the same bore?

Thanks.

David.

I would wager that is a measurement error or a replacement part.

Don’t know that I’ve ever seen a .541 slide tube in the USA.

Cheers,
Andy

A friend of mine has a 42 MT V too with the same slide measurement as mine, I mean, 13,75mm diameter.

dapezar wrote: ↑Fri Feb 14, 2025 1:03 pm A friend of mine has a 42 MT V too with the same slide measurement as mine, I mean, 13,75mm diameter.

How are you measuring the slide inner diameter?

It was measured in the workshop.

In the attached picture, you can see the measurement made by my friend.

dapezar wrote: ↑Fri Feb 14, 2025 1:51 pm It was measured in the workshop.

In the attached picture, you can see the measurement made by my friend.

It appears that you may be measuring the reduced diameter of the "swaged" tip of the inner slide, not the inner bore of the slide tube itself, which for a Bach 42 should be closer to 13,9mm (0.547 inches).

dapezar wrote: ↑Fri Feb 14, 2025 9:02 am Its not 23,89mm.

Is this a typo? 13.89 makes sense to discuss. I don't know what 23.89 is.

Those electronic calipers are notorious for giving inaccurate measurements. I always double and triple check my electric calipers against other measuring devices to see if they remain true.

I have a caliper at home that starts accurate in the first 2/10 of an inch. By the time I get to 1/2 an inch, it is off by .014 or .015 of an inch. I have heard many stories of others having issues with calipers like those as well.

In the shop I work in, we have measuring slugs that are made of a very hard alloy (so that they cannot be altered). We frequently check our measuring tools with those to make sure everything is accurate. The slugs are accurate to the .0005 of an inch.

Another thing to remember is that all inner slides are always chamfered inward. In order to measure the inside accurately, you must go in the tube a little distance, to the point where the tube is actually straight.

AtomicClock wrote: ↑Fri Feb 14, 2025 2:07 pm

dapezar wrote: ↑Fri Feb 14, 2025 9:02 am Its not 23,89mm.

Is this a typo? 13.89 makes sense to discuss. I don't know what 23.89 is.

Sorry, I mean 13,89mm

Try measuring at the threaded tenon end, where it goes into the bell side receiver

More than likely it's the standard 0.547" bore