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Distinguished SOTW Columnist/Official SOTW Guru
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Hi Guys,

I'm servicing a bunch of student instruments where the client is unhappy with the previous tech. Most are Jupiter student models with a few Yamaha student models thrown in.

In both cases, the Upper and Lower stack adjusting bars have the adjustment screw arrangement.

I know a lot of techs don't like these things (Reg Thorpe backs them out all the way and treats the adjustment as if the horn were a model without the screws).

On many of the horns, the screws are at the limit of their adjustment and it looks like rather than deal with the height of the bar, the previous tech has tried to get every last ounce of turn out of these screws and in so doing, totally rooted the screw slots.

I have managed to adjust the horns and get everything sealing and adjusted just fine without using the adjusting screws anyway, but I'm wondering because I will in all probability be servicing these instruments as part of an ongoing maintenance contract, whether I should leave them there or drill them out and replace them with new adjustment screws.

What approach do other techs take on school rental fleet instruments where cost/time is an issue and the school band committee aren't to keen to pay for parts/time.
 

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If there at there limit travel wise then the bar has been bent, re bend the bar and wind all the screws back in.

If you need to replace them then simply turn some threaded rod up and cut to suit, I dont even try to order replacements

Alternatively remove the screws and cork to suit
 

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In the shop I worked in the bid price quoted the schools was sufficient in most cases to fix the instrument properly. The reasoning was twofold:

1. When that instrument came back to us it would be faster and easier to repair the next time.
2. When that instrument went to another repair shop they would not see 2nd rate work coming from our store.

For the problem at hand, I would go with the Reg Thorpe advice. Removing the adjusting screw entirely would necessitate using too thick a cork between the foot of the key and the back bar. Most of the adjusting screws also are slotted on the underside so that they can be turned all the way in by removing the key.

A good way to explain the situation to the school group is that to repair their instruments the first time is going to cost more because you first have to undo the damage caused by the previous poor repairs, before you can do the normal maintenance repairs. That reinforces the idea that to have the instruments repaired properly even though it takes a bit more time and expense up front, will save money in the long run.
 

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The adjusting screw business is a classic example of something that appears to be a great idea but which often loses something in practice. The biggest problems that I’ve run across have been too small feet which dig into the cork (even tech cork gets chewed up on many of these) and stripped heads on the screws- usually caused by screws which won’t pass all the way through from the top and which then seize up when someone tries to turn them down farther than they were designed to to get more adjustment out of them than they were designed for. This is sometimes a result of bending of the mechanism somewhere but even more frequently the result of the feet having dug into the cork.
A simple solution is to take an appropriately threaded screw or bolt, dremel down the head to a smooth surface (similar to the top of a thumb tack) and then cut the body of the screw off at an appropriate length and cut a slot in the end of the screw (just as in a threaded rod end).
Screw this in from the bottom and then use a thin (.3mm) bit of tech cork on the mating adjusting surface. The smoothed top of the screw/bolt can be easily adjusted from the top by the slot- just as with the original adjusting screws and the large surface contact between the smoothed screw head and the tech cork will remain in adjustment about forever. Should subsequent need for adjustment arise for whatever reason, the adjusting screw, threaded in from the bottom, will extend out smoothly for its full range when turned from the top without the seizure problems that led to a mangled head on the original. Loctite may be used as desired required to retain adjustment if the screws turn too freely.
“Works for me.”
Ditching the things altogether in favor of traditional methods is also an option of course. That has two advantages. Pretty simple and it works.
 

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I have managed to adjust the horns and get everything sealing and adjusted just fine without using the adjusting screws anyway, but I'm wondering because I will in all probability be servicing these instruments as part of an ongoing maintenance contract, whether I should leave them there or drill them out and replace them with new adjustment screws.
I don't think I would drill them out to replace anyway.

I assume based on your description that the previous repairer "opened" the screws (from top side when assembled) most possible until the slot was ruined. At least on Yamahas that I've seen (I don't remember what Jupiter has) the screws have a bigger head with a slot at the bottom. If you want to remove the screws to replace you can remove the stacks and remove the screws from the other side where there's a slot left (or not?!).

What I would personally most likely do, is re-slot the screws while still on the instrument with a very small reversed cone bit in the micromotor (at around 40,000 RPM). Very fast and a new usable slot, no problem. Though the screws are at their most "open" position, so they should stick out some and I might use a type of cutting wheel instead (if there is enough space) since it won't ruin the bar (the reversed cone bit won't ruin the bar even if the screw is not sticking out).

You haven't mentioned that the screws are also stuck so I assume they aren't, the "missing" slot is the only problem and the threads are fine too. So I don't see a reason to drill them out at all, especially with the bottom slot available to remove them. If not and there are other issues, then other methods might be needed (I imagine you are familiar with this).

What approach do other techs take on school rental fleet instruments where cost/time is an issue and the school band committee aren't to keen to pay for parts/time.
If not stuck and no problem with the threads then I'd re-slot, each screw might take around 20-60 seconds I'm guessing, then use loctite after adjustment if necessary. Working as if there are no adjustment screws can work fine too. I might do that if the screws are stuck beyond salvation by re-slotting and a good screwdriver and it becomes too long for a budget repair like that.
 

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I look at horns with regulation screws a little different. I consider them as lost motion screws. Once I have the height I want on the F# key (which then sets tha action height for both upper and lower stack) I use the screws to eliminate lost motion and then regulate in the normal manor.
 

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On Yamahas they have the wide flanged underside which have a slot in them (which means they DON'T chew through the silencing material), so you can still screw them back in if the heads have been mashed. You will have to take the keys off to do this.

I usually remove them and slightly dome the flanges so they don't have any sharp edges that can dig into the silencing material.

Likewise I use these screws for minor regulation instead of screwing them right down well beyond their limit to regulate the closure of the uppermost LH and RH main action pads.
 

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I look at horns with regulation screws a little different. I consider them as lost motion screws. Once I have the height I want on the F# key (which then sets tha action height for both upper and lower stack) I use the screws to eliminate lost motion and then regulate in the normal manor.
I'm having trouble following this. Can you give a bit more explanation? My only experience in eliminating lost motion has been to adjust the feet cork, not the distance between the top of the key foot and the back bar.
 

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Thanks- as you know it's well nigh impossible to own a LeBlanc (Semi) Rationale and not wind up obsessed with adjusting screws of one sort or another...
Yup. That and Loctite rule my life nowadays :mrgreen:
 

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I look at horns with regulation screws a little different. I consider them as lost motion screws. Once I have the height I want on the F# key (which then sets the action height for both upper and lower stack) I use the screws to eliminate lost motion and then regulate in the normal manor.
Likewise, most of the time.
And I regard the cork as having a specific, dual function, compromising between damping noise and accurately conveying motion.

I consider it that compromise quite challenging enough without adding a third parameter of making linkage adjustments by cork altering thickness. That is why I make adjustments by bending.

BTW, those screws on a Yamaha have a slot across the head that contacts the cork. A raised ridge will gradually form on that cork, where the slot is. So when you tun that screw for adjustment, the non-grooved part of the screw will be pressing on a very narrow raised ridge. Soon after, that ridge will compress, altering that fine adjustment. So just how reliable are these "precision" adjustments made by turning screws on Yamahas Hmm.

I think properly carried out bending is probably more reliable.
 
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