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When youse guys build a horn, do you lap the slides when the valve machine is off the horn, or do you wait until it’s assembled?

There’s pluses and minuses for both methods, which do y’all prefer?

Ideally it shouldn’t matter…but things are subject to subtle stresses when mounted, so it’s probably best to do all that stuff once slides are mounted.

I tend to eventually put finishes on instruments, so I certainly do it before any finish is applied, to make sure that the process is going to be successful and satisfactory, and that nothing will need to be moved.

Yes, that makes sense (and is the way I usually do it, just for the reason you present) - but I thought it might be easier to thoroughly clean out all the lapping compound before the valveset is affixed to the instrument....?

A gasoline-soaked cloth swab followed up with a really strong liquid detergent and an aggressive hot water rinse does a good and economical job.

Actually.....I first build up the individual slide assemblies including making them parallel, braced and lap them in before I match them to the valve casing. THEN after the slide works correctly, I fit the individual slide assemblies to the the valve casing/knuckles. Why hook up defective parts and then have to trouble shoot later?

Matt Walters wrote: ↑Sun Apr 25, 2021 9:28 am Actually.....I first build up the individual slide assemblies including making them parallel, braced and lap them in before I match them to the valve casing. THEN after the slide works correctly, I fit the individual slide assemblies to the the valve casing/knuckles. Why hook up defective parts and then have to trouble shoot later?

That's how I do it, too.

I build the slide on my homemade alignment jig. Once I am happy with it I then lap the two outer legs to where the dry action is where I think it needs to be. Whenever it is practicable I install the outer legs to the slide and then solder a brace to the outer legs to keep everything aligned when assembling the slide to the horn. My slides are aligned before they ever see the valve section and do not go onto the runners until they meet the slide legs without any deflection.

I like Joe's idea of using gasoline instead of mineral spirits and may try that. I have never found an adequate substitute for "chloroethane" as a degreaser/solvent, and I do not always get good results from low odor mineral spirits.

I do check sets (inside/outside) tubes to make certain that they fit/slide nicely (enough) as individual tubing pairs, but - unless I can see that my calipers will not fit on the instrument or that my coplanar line-of-sight will be blocked, I do usually tend to just build stuff (from the beginning) on the instrument.

With *one brace between the outside "legs" - and the only other stabilizing factor being a somewhat-flexible slide bow, slide assemblies aren't absolutely stable until they're mounted...and (even then) can be "coaxed" (more than) a tiny bit, if encouraged strongly enough. Brass is soft, and (even) one-piece braces are a tiny bit stretchable...as certainly is hardened-state lead solder.

I've found that - when I build slide assemblies **off the instrument, and mount them later (and sure: I've done that plenty of times) - I still have to "mess" with them (if I'm interested in ***0.000" from end-to-end). ...so I prefer (again, UNLESS calipers won't fit on the instrument OR if coplanar line-of-sight is blocked from view) to just do it once.

I will admit (once again) that the compact Holton tuba (just completed) is the first "project" that I've ever "free-styled" (begun and worked from beginning to end with NO "plan", whereas every other project was planned down to the very last brace...which defined most all of them as a bit boring, as they were all already built "in my head"), and - being "free-styled", that greatly increased the tendency to just "look, think, conceptualize, and stick".

If results are excellent (whether approaches are methodical or haphazard), there is not a "wrong"...particularly not if a chosen successful approach is also a time-miserly approach.
_______________________________________
*...ie. still: with the potential for this to occur:



** I actually DID build THIS whiz-bang OFF the instrument, but ended up taking it apart (because it didn't appear aesthetically aligned TO the instrument's bugle) and rebuilding it ON the instrument...so that pre-assembly (this particular time) proved to be a time-waste:
(...and yes, there's more hand-ragging to do now than otherwise would have been necessary, but Mrs. bloke is always asking me to do stuff related to her endeavors, and I can barter labor for labor.)


***It's not-at-all uncommon for slide sets on high-end European-manufactured instruments to be out as much as 0.010" end-to-end...and - with particularly long slides - that can even approach .020". LOL...It's not uncommon to encounter Asian instruments (from particular factories) with slides that are out of parallel up to 0.100" and out of plane by 0.200" (When some of those slides are pulled, they ring like a tuning fork.) The closer to perfect, the less lapping is required, and the easily it is to get slides to "float" without a loose fit...and - with exceptional alignment - "lapping" can (sometimes) only require less than a minute of time...which is cool...when someone is lazy (and yes: I'm lazy as WELL as undisciplined ← truth).

gasoline: also seems to often work better as a paint thinner (than "paint thinner"), when spraying enamels on trailers, farm equipment, mowers (metals) etc... Of course, I ALWAYS use the recommended substances, and COMPLETELY according to instructions.

the elephant wrote: ↑Sun Apr 25, 2021 10:39 am

Matt Walters wrote: ↑Sun Apr 25, 2021 9:28 am Actually.....I first build up the individual slide assemblies including making them parallel, braced and lap them in before I match them to the valve casing. THEN after the slide works correctly, I fit the individual slide assemblies to the the valve casing/knuckles. Why hook up defective parts and then have to trouble shoot later?

That's how I do it, too.

I build the slide on my homemade alignment jig. Once I am happy with it I then lap the two outer legs to where the dry action is where I think it needs to be. Whenever it is practicable I install the outer legs to the slide and then solder a brace to the outer legs to keep everything aligned when assembling the slide to the horn. My slides are aligned before they ever see the valve section and do not go onto the runners until they meet the slide legs without any deflection.

I like Joe's idea of using gasoline instead of mineral spirits and may try that. I have never found an adequate substitute for "chloroethane" as a degreaser/solvent, and I do not always get good results from low odor mineral spirits.

My experience is similar - I make sure the circuit is co-planar before affixing it to the valve block, so that it will move readily when dry - I hadn’t thought of lapping it before installing it - maybe I’ll try that next time.

Also, I like the idea of using gasoline. I usually use naphtha, which doesn’t quite “cut the mustard” in my opinion. Gasoline definitely evaporates quicker - does it leave any residue?

I usually chase gas with a strong liquid dishwashing detergent - and then high-velocity hot water.

With the slides on my Holton, I would’ve had to have gone all the way back to the house to get the dishwashing liquid, but (for some odd reason...??) an aerosol can of “scrubbing bubbles“ was out in the shop. I sprayed that on a brush, and it seemed to clean the gasoline (and last little remainder of crap) really well. The first pass with the slides and some oil didn’t pick up very much “black”...as it does require a few oilings (and removal of oil) to get slide pairs super-duper clean, because the texture of those two articulating surfaces - of course - holds on to a tiny bit of filth.
For some reason or other, I’ve always tried inexpensive household products first.
...just as I tend to lubricate my instruments with lamp oil, 30W oil, STP oil treatment, and possibly combinations thereof.

one last comment about slides:
My goal is to get them to work as nicely as they need to work - on my personal instruments - with nothing more than lamp oil. Putting nothing but lamp oil on my valve slides (particularly #1 and #2, as they are so close to the valves), there is no grease that can migrate into the valves - which would gum up the valves.
I would tend to suspect that - when some people complain about this-or-that brand of valve oil gumming up, the oil is being wrongly blamed, and it’s just slide grease migrating into whatever oil they happen to have chosen.

pre-building slides:
It works pretty well with the simplest assemblies, but the more complicated they are, the more factors are involved. Even by the time we get to a front-action “over-under” #3 circuit, we encounter end-points which are nearly impossible to pre-measure, as well as multiple alignments that depend on each other, and which are altered by each other.
fwiw, my lower slides always slide as nicely as the uppers (alignment-wise), though I tend to not “lap them in“. Sighting across planes (with the ability to “see“ a perfect 180° angle) - and coming up with creative ways to fit calipers on instruments - are both handy skills.