Outer Slide Tolerances

[sstelmack]

I was recently loaned a brand-new horn for a performance. I had this horn for about 2 weeks. About a week in I noticed the slide was not working the way I would think a new horn should work. Thinking I tweaked the slide alignment I brought it to a tech to check it out. He measured it up and found that the outer slide was out of parallel by .006 of an inch. He told me that the slide must have been assembled that way and it wasn't due to damage. He tweaked the inner slide and it did help, but he stated that it was going to be an issue for the life of the horn unless it gets fixed.

My question is, what is an acceptable tolerance for the outer slide when it comes to being parallel?

This being a high-end professional horn I would think that it should be as close to perfect as possible, but I don't know what that would be in an actual measurement other than 0.000.

My new horn is on the way, and I am going to have it measured up as soon as it gets here. I would just like to know at what point should I refuse delivery and make them fix it. Having the inner slide aligned is not a big deal, but the outer is a pain and expensive. I would not want to have to pay to have a horn fixed that was just purchased as brand-new.

Thanks!

[ithinknot]

Don't worry about the numbers. You knew the action wasn't satisfactory on this one - that's enough of a giveaway. And if you're getting a new horn, you shouldn't have to have the inner aligned either (even if this is a lot less annoying than fixing the outer).

A factory should have established tolerances, but quoting them isn't necessary helpful because it depends so much on the location of the discrepancy.

In the wild, 5 thou might still feel pretty decent if the inner matches the outer in 1st, and the error only shows up in 7th where standards are lower and the inner can flex a little to suit. But the other way round might have much worse action. Or the outer could measure identically top and bottom, but the action still stinks because any of the four tubes might not have been properly straightened. The point at which a number becomes a problem also depends on the clearance between the stocking OD and the ID of the outers, which varies between brands.

Don't worry about the numbers.

[Macbone1]

Modern American slides have much closer tolerances than the classic horns, starting in the 1990s(?) I believe. Makes for a smoother feel, which is counterintuitive because naturally you would think closer "rubbing" would equal more problems. Might be tougher for techs to repair them, but once you use a good modern slide it's kind hard to go back. The old ones feel loose and "floppy".

[ithinknot]

Modern American slides have much closer tolerances than the classic horns, starting in the 1990s(?) I believe.

True in some cases, but not all... e.g. old Bachs have much tighter clearances than recent ones, and than various other current manufacturers.

[greenbean]

Your new slide should be within .001 or .002 of being parallel.

[timothy42b]

Modern American slides have much closer tolerances than the classic horns, starting in the 1990s(?) I believe.

I would think probably so.

Makes for a smoother feel, which is counterintuitive because naturally you would think closer "rubbing" would equal more problems.

Um, not really. You may think this is nitpicking, but it's actually an important distinction.

Tolerance is how close you make the slide to the design specification. Clearance is how much distance there is between surfaces.

You could design a slide that has 1/4 inch between inner and outer, and build it to a very close tolerance, and it wouldn't play very well.

[Doug Elliott]

Virtually nobody ever uses the word "tolerance" correctly.
It's intolerable.

[Macbone1]

Lol. Well l was never a machinist, so....

[ithinknot]

Tolerance is how close you make the slide to the design specification. Clearance is how much distance there is between surfaces.

Yeah, whoops. I've gone ahead and brazenly falsified the historical record (read: edited).

[brassmedic]

I'm afraid that ship has sailed. The Allied Catalog has referred to it as "tolerance" for as long as I can remember.

20220311_120733.jpg

My pet peeve is "gooseneck". A gooseneck is usually an object with a sharp bend in it. Trombones have a neckpipe, which may or may not have a slight bend. It's a neckpipe because it sits next to your neck. I think someone along the way saw the word "neck" and attached the word "goose" to it for no other reason than that they had seen those two words together before, and unfortunately it stuck.

[hyperbolica]

Tolerance is how close you make the slide to the design specification. Clearance is how much distance there is between surfaces.

I was going to come here and post this same thing exactly. I'm a mechanical engineer, and one of the things I do is make manufacturing drawings for parts and products. On drawings for parts that are manufactured, each dimension has a "tolerance". This is typically X +/-Y so 1.000" +/- 0.005". The 0.005" is the tolerance. It means that acceptable parts can be in the range of 1.005 to 0.995.

This kind of over simplifies things, because that's just the diameter. Other things such as the straightness, twist and planarity can also vary. But we'll go with the simplified case for our purposes here.

Tolerance is a statistical measure that has to do with repeatability, it is specified on the design drawings and measured after manufacturing. You're trying to get as many parts as possible to simultaneously fit together and allow the mechanism to function to an acceptable level. You'd get a plot of the measured values of all of the slide tubes manufactured from a given dimension from a drawing, and it would produce a bell curve, and a certain percentage of the parts would be accepted or rejected by the quality control person or robot or whatever. The process can tolerate this much deviation. Some tubes may be rejected, some may be reserved to be used with mating tubes with specific measurements.

And then you have to worry about how many of those mating parts from opposite extremes can fit together, for example, an outer slide at the low end of the tolerance and an inner slide at the high end of the tolerance - will that work acceptably? And then you have to talk about variations in assembly methods - soldering by hand has some variation. Tolerancing is a complex part of the design and manufacture of a product, even with the simplest of systems, like a trombone slide.

If you're talking about the measurements of an individual slide, that's just as someone else mentioned, clearance.

[timothy42b]

Tolerance is how close you make the slide to the design specification. Clearance is how much distance there is between surfaces.

I was going to come here and post this same thing exactly. I'm a mechanical engineer, and one of the things I do is make manufacturing drawings for parts and products.

For completeness we should mention that, to a mechanical engineer, there is another sin that is equally bad if not worse. (though not as bad as a side load on a sliding joint)

That is to confuse stress and strain. NOT the same thing! Mohrs the pity.

[afugate]

For completeness we should mention that, to a mechanical engineer, there is another sin that is equally bad if not worse. (though not as bad as a side load on a sliding joint)

That is to confuse stress and strain. NOT the same thing! Mohrs the pity.

I see what you did there... Don't get too stressed out about it.
--Andy in OKC

[hornbuilder]

Your new slide should be within .001 or .002 of being parallel.

Without naming names (for obvious reasons) one well regarded larger shop has an acceptable range of +/- .005 on handslide outer tube parrallel.

I personally build slides to + .003 allowable. (No "-") but that + .003 is rare, I usually hit .000 to .002

[sstelmack]

Your new slide should be within .001 or .002 of being parallel.

Without naming names (for obvious reasons) one well regarded larger shop has an acceptable range of +/- .005 on handslide outer tube parrallel.

I personally build slides to + .003 allowable. (No "-") but that + .003 is rare.

Perfect! Thanks!

[GabrielRice]

Obviously, this should be a factory warranty issue. But if your tech could tweak the inner slide I don't understand why he couldn't tweak the outer slide to match. He would have to burn a little lacquer to do it, but the lacquer isn't going to last forever anyway.

[sstelmack]

Obviously, this should be a factory warranty issue. But if your tech could tweak the inner slide I don't understand why he couldn't tweak the outer slide to match. He would have to burn a little lacquer to do it, but the lacquer isn't going to last forever anyway.

It can be done. But on a brand new $5,500+ horn I'm expecting it to not need any work like that. And with how long these horns take to order from the factory I'm not excited about the idea of sending it back for work.

My horn came and the slide is about perfect on it. I still need to take a caliper to it for exact numbers but it's silly smooth at the moment.

[GabrielRice]

It can be done. But on a brand new $5,500+ horn I'm expecting it to not need any work like that.

Reasonable.

Perfection is elusive at best, though.

[hornbuilder]

Quote Hyperbolica.... "Tolerance is a statistical measure that has to do with repeatability, it is specified on the design drawings and measured after manufacturing."

Sometimes.

For a period of time, I was in a position working with new slides from a particular manufacturer. It was obvious from the examples inspected that slide assembly was being entrusted completely to the use of jigs, with seemingly zero measurement occurring after assembly. The range of variability in degree of parrallel, straightness and scew was stunning!! The worst case was a slide that was .065" out of parrallel!! Not to mention the lack of straightness and obvious skew! Yet it had been sent out as acceptable.

It is often suggested to people that "defective" slides should be sent back to the manufacturer for correction. That assumes that your and the manufacturers expectation of "correct tolerance" match.

[CharlieB]

My new horn is on the way, and I am going to have it measured up as soon as it gets here. I would just like to know at what point should I refuse delivery and make them fix it. Having the inner slide aligned is not a big deal, but the outer is a pain and expensive. I would not want to have to pay to have a horn fixed that was just purchased as brand-new.
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You might think of a different approach.........
Forget about measurements and evaluate the slide based on performance. Hold the properly lubricated slide horizontal and gradually tilt it downward until the outer will move its full length by gravity alone. My slides do this at 15 to 30 degrees below horizontal.