Basic Slide Straightening
Simple Straightening and Aligning of Trombone Hand Slides
There is no trouble with trombones. They are just another job, no harder nor trickier than any other job that requires a little skill to do. After all, every job requires that you know something in order to accomplish it.
There have been many fine tools developed over the years to help with this particular endeavor. Unfortunately, some of them have been misused or improperly used over the years; the N11 Trombone expandable burnisher comes to mind.
No talk of straightening and aligning can begin until the slides are properly cleaned (see related article on cleaning) and the dents, kinks and creases are removed from the tubes (or rails); because dents and dent work contribute to misalignment. First, when the dent is put in, it also bends the tube. Also, when you take the dent or bend out you are bending the slide tube the opposite way but, maybe not in the same places or with the same force, exactly; coupled with the fact that a dent is very localized and a bend covers more area. Additionally, a dent or crease may cause the rail or tube to be ovalized along with everything else that is going on. (The new N87A trombone pliers tend to eliminate most of the problems encountered in these regards.)
There are two basic kinds of straightening jobs you are going to run across. With one you are going to be able to just do some minor dent work, straighten and align the slide rails and let it go. Hopefully, most of them will be in this category. They will not be exactly perfect but, they will be perfect enough to satisfy even the fussiest player. (Unless, they have their own leveling stone; in which case they don't need you anyway but, now we are being theoretical.)
The second of these are the ones where you have to unsolder the hand slide crook (end bow) to remove the various built up stresses in order to even be able to straighten the tubing and so you can effectively start over fresh; eliminating any internal stresses or pressures.
It becomes clear, very quickly, that you are going to have to know when to jump from job one to job two and that job two is going to be more costly and more accurate than job one. Also, you are going to have to be able to know or recognize this when you first see the instrument to quote the repairs necessary and hopefully avoid "the phone call" where they begin to wonder about your motives, integrity and honesty.
This is, in a sense, a "repad" of sorts. That is, you have changed everything, so that you can do everything over your way and take complete credit for the result; and repads cost more for that reason. Your customers are all going to want job one; or rather, job two at the job one price. ~So, here is where we start.
Most of the time the slides just get mishandled or banged around a little bit where there is no noticeable damage. This slide "looks" new and/or undamaged, and other than not working, the slide looks just fine. It is hard to justify a large expense to customers on a supposedly "simple job" like this and indeed you have to develop the skills to be able to produce and complete this job as job 1, most of the time, and be able to explain it clearly as well.
A few quick "rules": Never twist a slide. That is, do not grab and attempt to change the planes of the slide rails by twisting. It just doesn’t work, most of the time. That being said, if it is very minor, you may try to 'tweak it' a little but, if it does not produce immediate results you are wasting your time. This is also a point where a bad connection ring solder job may show up. Now, unless someone grabbed the slide and twisted it to begin with, you are going to have to follow the regular route of repair. Most bent slides, other than ones that were grabbed wrong by an unknowing person, across the rails, got bent by dropping and slithering across the floor. (Most dents are caused by music stands, in that same vain of thought.) Once again, twisting seldom works.
Never unsolder a slide. With any dent and alignment work, all we are doing is reversing the action of whatever caused the damage in the first place. With any dent, we are putting the distorted material back where it came from and then holding it there by actually bending it too far or even passed where it was originally and letting it spring back to where it looks good and/or works good with the surrounding area. (I guess this would be the true "skill"; mastering the 'spring back'.)
Likewise, on a hand slide, all you are going to do is analyze and bend back the errant rail or tube. Now, here is where it may get a little dicey. When you bend on one rail, the other rail is going to bend sympathetically because they are hooked together by the end bow and the brace (on the outer slide) at the other end. So, you have to both allow for and use this to your advantage to be successful. If you are not successful or the damage is too severe, you are going to have to remove the end bow, let everything become relaxed and then straighten everything perfectly so you can solder it all back together; aligned better than new. With care, you can do this without badly damaging the lacquer, most of the time.
With proper heat application and care, you can make this very unobtrusive. Never use a hammer on a trombone slide. Hammering does two bad things: It work hardens the material and it thins it. Quickly. Nowadays, it is best to roll the dents out using a smooth straight mandrel and a pair of pressure adjustable rollers. (Read: N87A trombone pliers and proper sized N53 trombone mandrel.)
This combination is unmatched when it comes to dent removal and straightening. Because, as you are taking out the dent(s) you are also forcing the tubing to lose the dent while pressed against a perfectly straight and round surface. So, you are actually re-contouring, re-forming and straightening at the same time that you are removing the offending dent(s).
There have been many good, even great at the time, tools used for removing hand slide dents. The N53 and N52 trombone slide mandrels and the N12 3/4 Ring (using, at least 5 day old bar of ivory soap as lube) along with the chromed N11 type expandable tools were and continue to be very valuable in this area as well as the old style N87 dual roller tool. Sometimes these tools were misused, but overall they did an excellent job anyway if used with the skill and care the job required. We never had any trouble with any of these tools and never had any instrument damaged by them. However, there is only so much any tool can do and it is up to the operator to know when that point is reached.
Actually with some experience, the operator should know ahead of time, before the maximum capacity is close at hand. In forty years, we have never gotten a slide so hard that it split or cracked from what we had done. We have repaired literally thousands of rental returns and never had to replace a slide rail due to any such perceived over hardening. If you do, you have misused the tool by over expanding and probably overworking as well. As an aside, we tried to purposely expand an outer slide where we needed .001" larger bore for the inner slide off another horn to fit. After nearly an hour of hard work, blistered hands and aching fingers we had expanded it a total of ZERO.
Remember, we're going laterally, not rotationally.) We also, most likely, did the repairs on most these same slides through the rest of these students high school marching band careers without incident. Yes, we did have older rotted slides split open because they couldn’t take the strain of repair, or slides break where they were cracked due to severe bending or previous bad repairs by others, but that is different.
Of the two or so rails we replaced in a years’ time over the years, most were marching damage or just old horns that had given up the fight. It is just so easy with today’s new tools, to do a quick, easy and good job.
One more thing: dents in the end bow. Up until recently the only way to remove dents in the hand slide bow was to “float” a ball down in there and attempt to smooth it out if it wasn’t too bad or just remove the end bow and use a rod and ball to remove any dents and straighten everything, align it all and re-solder it together.
Now, there is the P53 trombone dent ball driver/retriever. This tool allows you to control the position of the dimensional N57G ball you are installing into the hand slide bow. Keep in mind, the fitted ball will still be approximately .010” to .020” smaller than the tubing due to the solder joint shrinkage, but you are still better off than before, because of the ease of placement and removal. Well, the dents are out, so let’s do the actual straightening and aligning.
What’s great about slide repair is that there really isn’t all that much to it. First, if you are seriously going to do quality slide repair, you are going to need a ground stone or other useable flat surface. This will determine the finality of your job.
The difference between straightening and aligning is just this. Straightening is what you are going to do to the individual slide tubes and aligning is what you are going to do with them once they are all straight and then you are going to solder them back together.
After the slide has been properly cleaned and all the dent removal is completed, the next step before reassembly or soldering is to make the slides work smoothly. There are about 12 places to check for straightness and another 8 or 10 to check for alignment, depending on how you are counting.
To begin, place the outer slide assembly on the stone one rail at a time and make these observations. As you roll the slide tube toward and away from yourself, look at the light coming in view between the rail and the stone. Determine which way the rail is bent and push the rail the other way by putting the open end of the slide on a slightly formed block and pushing with care and aplomb. We have a radiuses notch carved into a wood block lower down on our P91 stone stand. This way you don’t distort the tube very much, if at all. If you have to put a ball in the tube to keep it from collapsing, you are wasting your time and somebody’s money. If the rail or tube is that delicate, how long do you think it is going to last; if it makes it off your bench at all. Replace such a rail.
Your customer is NOT going to like bringing the slide back to you the next day for the same thing you just supposedly fixed. You should have known better in their eyes. And you won’t like working for free. If they won’t pre-approve the work, don’t do it AT ALL. (It would be cheaper for you to hand them $20 and send them to a competitor.)
Check and correct each of the four long parts of the slide rails. Next, check the 4 stockinged areas the same way. Now, roll the stockinged area tightly on the stone and check the elevation of the long part to see if they are concentric and aligned with each other on the inner slide assembly. On the outer slide, you will have to push the stockinged area down tightly on the stone and see the elevation of the long part as you rotate the unit. This is very important, it all has to be straight and concentric. If the end bow is still soldered on, you are probably going to have to do some heavy compromising here to be sure. All you can do is the best you can with whatever skill level you have.
The goal is to get it straight and aligned without taking it apart. (This is an acquired skill.) Twisting only adds to the problems and the inherent or interior tension. The inner slide assembly is much easier. No end bow. Once again, check the long straight parts by rolling them forward and back observing the changes in the light. None of them are perfect, not even from the factory. Make the necessary linear corrections.
There is a necessary caution here. The upper rail, the one with the venturi inside (mouthpiece side) will give you a little fight sometimes because the venturi tube is a slip fit into the slide tube and the mouthpiece fitted side is soldered in sometimes before it’s soldered into the cork barrel and sometimes after, so this side does not move, bend or react as easily. When you are straightening the rail in this first 8 or so inches, the two tubes will sometimes move internally since they are only hooked together on the one end (not internally) where they may or may not slip smoothly, if at all. This will cause the movement of the slide rail to sometimes become somewhat animated or jerky in movement. It won’t be free flowing as you may be used to. If this happens only slightly, you will get radical results and may not understand why. Now, you do. You may have to bend this portion with your hands physically, not sliding down the tube as before. Go slow. Occasionally, the interior end will become corroded together with the rail and magnify these difficulties. AGAIN, Go slow.
Your setup can be better than the factory's because you want it to be and because you care. Plus, you have to look the actual customer in the eye. Now, lay the slide tube on the stone with the stockinged area toward one end of the stone. The free end of the stocking will then be elevated above the stone because of the angle created by the difference in diameter of the two parts. Roll the tube and see if the stocking goes up and down or maintains the same angle of light as you rotate the unit. Be very slow and methodical here; you don’t have much to work with and the slide lock may also try to interfere with your progress and observations. Since you have already checked the stocking to see if it is straight itself (You did do that, didn’t you?), now you can bend the stocking to be straight with the rail, if the angle changes (concentricity). Do all four of them.
Now, with a set of calipers or dial calipers (the measurement is not important here, it is the feel) or if you have calipers in thousandths or millimeters, you can “compare” and get it so the slide rails are perfectly parallel and they will then “feel” the same. Like I said, the number doesn’t really matter, as long as they are the same. It’s probably better if you don’t know a number, what matters is how it works. Don’t get stuck on a number.
If everything went back where it came from in the case of the soldered together unit. All you will have to do is bend the inner slide to fit the outer slide that you have aligned. If there has been no soldering on your part and the slide was built right in the first place, everything should be aligned about now.
If you had removed the end bow (hand slide bow) and done all this aligning, you probably want to solder the end bow back on about now. Check the parallel with your calipers again, and then lay the slide unit down on the stone with the stockings hanging about an inch over the end. Lightly push on one of the stocking ends down and observe which rail and how far it elevates. Now, push the other rail down and observe the same thing. If one came up before the other they are not truly aligned yet. Tweak the hand slide brace the proper direction to equalize the stress and try this simple test again. When both sides lift equally, the hand slide is parallel in that plane. The dial calipers aligned the plane 90 degrees off of this one so I guess you could say it is now straightened and aligned. (You can do this with the inner slide as well.)
Once this work is done, install the aligned inner slide into the aligned outer slide and lay it on the stone. Physically check and confirm that everything is correct and then check to see if the end bow will install without changing anything. If not, bend the bow whichever way you have to, to get it to go in without disturbing any of your other measurements.
Once that is accomplished, it is very important to solder this together WITHOUT distorting your established dimensions with the heat. Only use enough heat to melt the solder. Then put the solder on the brass and wave your torch near the heavier side of the joint until the solder goes in, in slow motion. The heat is applied away from the solder and on the side where you wish the solder to draw to.
This is usually the heavier side. (Remember, solder follows the heat.)This is called "cold soldering" because it preserves all of the alignment work up to now. Yes, we do use liquid solder flux using an eye dropper to apply and have cleaned the affected areas before I started. Additionally, you can use the liquid solder flux to "half cool" the solder joint without crystallizing the tin in it, which we believe weakens the joint and adhesion. (You can test this theory with a sax post and your L13 slide hammer tool while "lifting" out a dent.) We try to never use water to cool as it cools too quickly and can change the tubing relationships as well as weaken the joint strength of the solder.
Some minor touch up work and this should be a finished job. One last time "dry rag" the slide rails under pressure; to remove any dirt, dust or moisture and it's a done deal.
Ferree's Tools-"Because they work