vature on the mouth-pipe. Any dents in the connecting tubes between the valve casings
and outside slides are simply removed by using the ball end dent rods as previously de- scribed.
The bell presents the next major prob- lem. The bell flare dents are removed by first gently hammering the bell ring into its proper place with a rawhide mallet. Next, burnish the dents from the flare over the saddle iron or horn stake, taking a small portion at a time, then blending the burnished sections so that the smooth curved feel of the bell is main- tained. The worst dents on a French Horn usually occur on the first turn of the bell. These dents should be gently pushed up after which the part must be burnished on a curved rod to maintain the proper curvature. thereby eliminating the stretch marks that will take place. Final finishing of this part is done by light emerying and huffing. We must reach as
far as possible in the bell with a circular rod with a ball on the end to try and cut down the amount of plugging to a minimum. This can be accomplished to a point past the finger rest opposite the third valve. We must then
remove the dents from the back turn of the bell with a dent rod that is curved almost in the shape of a question mark. (?) This type rod will allow you to reach the dents to a point opposite the first valve. This will leave a dis- tance of approximately four to five inches that must be plugged out. This is accomplished by using the larger set of dent plugs. The one troubling factor to be careful of is the fact that
the bell will have a tendency to want to straighten itself out of its curve when all this dent removal is being done. To eliminate the chance of this happening, solder a bar across the turn of the bell. This will hold the curve of the bell intact. When all the dents are
removed, remove the bar brace, finish the dent work by emerying and buffing. Resolder the bell in place.
Rotary Valves
There are two types of valves, namely, the pump type and the rotary type. The pump type is the average valve used on the regular brass instruments. The rotary valves are the type used on the old Italian trumpets etc. and
on French Horns. The rotary valve is basically the same even though the action is of two varieties namely, string action and machinery action. The rotary valve is actually tapered
Curved ball end rod used for removing dents from French horn bell.
Rods should be curved to fit the shape of
part to be burnished. Rotary and string actions
Holding bar prevents tubing from spreading when being plugged out.
slightly and must be a perfect fit in the valve casing. The top stem of the rotary valve is also tapered to fit the tapered tube on the top cap of the valve casing. The bottom plate which holds the rotary valve in place must be a perfect bearing surface in its tube over the bottom stem of the valve. This plate has marks there on. The mark on the outer edge must be aligned with the mark on the valve casing. The mark on the tube of the plate is the guide mark for the distance the valve must be allowed to turn in the casing to properly align the portholes. This turning allowance is determined by the thickness of cork bumpers on the top cap. These bumper corks are cut to a point that allows the marks on the bottom stem to correspond to the mark on the bottom plate. After the bottom cap is screwed in place. assuming that the valve and the casing are fitted and cleaned properly, if the valve binds, it is a sure sign that the bottom plate is not set perfectly. To correct this, tap the top stern very lightly with a rawhide mallet. This will allow the valve to work freely. The valve must be completely free to give the proper allowance for spring tension to operate the valve.
a. Valve Stringing
Valve strings on a rotary valve can be either fishline, nylon, or gut about the thickness of a violin gut A string. This string is tied on in the following manner:
Put a knot in the string about one inch from the end. Put this string through the hole in the valve key from the outside to the side nearest the valve. Bring the string past the valve stem around the back of the same stem. Coil it around the string screw. Pull the string to a point that allows the valve key to come to the desired height. Tighten the string screw allowing the string to continue around the valve stem. Complete the circle of string around the valve stem and put the string through the front hole in the valve key next to the string screw on the valve key. Draw the string tight around the string screw on the key. Tighten the string screw. The last coil pulls the valve around when the key is operated and the first coil uses the spring tension to return the valve to its original position. If the string is not taut in both positions, there will be lost motion in the operation of the valve.
b. Machinery Action
There are two specific types of machinery action. The difference is in the spring action.
The first type utilizes the same type springs as the string action valve. The spring is wound around the tubular hinge of the fin- gerkey. Solid pieces of German silver are the joiners between the valve stud and the fin- gerkey. To give mobility to these parts, they are hinged together. The rods that act as pins between these lever bars, although riveted on each end, must allow the tubular hinge to be perfectly free moving. In this manner, the levers take the place of the taut string. The second type machinery utilizes the flat type coil spring, such as found in small clocks. This flat coil spring is inserted in the barrel of the fingerkey, hooked to the small slot in the barrel. The opposite end of the spring is hooked to the hinge rod of the fingerkey. The tension of the spring is applied by winding the post leg of the key assembly.
Use of the Drawplate
Through the facilities of the A.R.S. and the Eastern School laboratories, another use for the drawplate was discovered. Patches on tuning slides, mouth-pipes etc. can be perfect- ly curved by use of this method. After the shape of the patch is cut from sheet brass, the patch is then annealed. Place the patch
against the tubing it is to fit. If the tubing is not tapered, insert the tubing, with the patch held against it, into the correct size hole in the drawplate. Smoothly draw the tubing through this hole. The patch will come through as a perfect fit to the tubing. In many cases, it is wise to gradually work one’s way to the per- fect’ size hole. If perfection is not achieved on the first try due to the temper of the brass, repeat the procedure.
Bending Tubing
Since tubing will have a tendency to fold when bending into the proper place or shape, we as repairmen fill this tubing to make it into a solid rod. Firstly, the tubing must be
annealed. Secondly, the tubing must be packed or filled solid without air pockets. Some people use sand, pitch, or lead as the filler. It could even be filled with a coil, spring. The material preferred by most repairmen is
SEROBEND. It is a material similar to actual lead. However, its fusion or melting point is that of boiling water. This material is easy to work with, both in filling the tubing and in removal of the material. The end of the
annealed tubing is plugged. The tubing is filled with the boiling water that is in the same pot as the water lead. The water lead is poured into the tubing, thereby forcing the water out of the tubing. When the tubing is perfectly filled, it is carefully lifted out and allowed to cool off slowly. After the lead has cooled so that the tubing is now a solid bar, light taps with a dent hammer will give you assurance that the tubing has no air pockets. At this point, the tubing can easily be bent into any desired shape. Small blisters may appear at the inside curvature of any bend. These
should be tapped back down in position as fast as they appear. Do not wait until the com- plete bend is accomplished. If the tubing is not perfectly filled, the tubing will have a tendency to crease and crack. There are bending
machines on the market that do not need to have the tubing filled prior to bending.
However, these machines do require a special die for each bend that is to be made.
Therefore, they are not practical for repair- men. Since any bend that a mechanic has to make has to have a decent radius, it is wise to make these bends around a piece of wood doweling.
Use of the Valve Casing Lap and Valve Block
The valve casing lap is a tool used to dress out small imperfections in valve casings, such as small nicks, clogged corrosion, or it may also be used gently to dress out a casing to a more perfect true round. There is a valve
casing lap on the market which has lead sleeves. A piece of wood dowel, split in the center, with an inserted small wedge will have the tendency to act as a casing lap since the wedge will give it enough spring to allow the outside diameter of the dowel to press against the walls of the valve casing. This lap is used with pumice stone and oil to grind away imperfections. The lap must be used in a twisting up and downward stroking motion to eliminate the possibility of continual stroking in the same position, since this would cause grooves instead of a smooth grind.
The valve block consists of two pieces of wood hinged together with an oval shaped hole between the two blocks. This allows suffi- cient spacing around the average valve so that slight pressure can be applied while using the block. The block is used with pumice stone and oil against the valve with a stroking motion while the valve is turning slowly in the lathe. This stroking of the valve eliminates the possibility of grooving the valve.
Testing for Leaky Valves and Slides
a.Valve testing
Since the air passage must be blocked when testing for a leaky valve, we must test each valve individually. To test the first valve, remove the first valve slide. Place thumb against the lower tube extending from the valve casing. Press the first valve down. Now blow air or smoke through the mouthpipe of the horn as hard as you can. If there is a leak, you will be able to feel the air escaping. If you are testing with smoke, the smoke will escape through the valve caps if the valve is leaking. if the smoke comes from the other valve cas- ings, it is a certain sign of a leak on the first valve. The second valve is tested by removing the second valve and repeating this proce- dure. Likewise the third valve. To eliminate the possibility of cross leakage while testing an individual valve, it is wise to grease the two valves that are not being tested at the time. This grease is easily removed with kerosene, with-out damage to the horn. By the same token, the slide should be sealed in a like manner. In this fashion, only the valve in question is actually being tested.
b. Slides are tested in the same manner. However, the slide itself must first be tested off the instrument in order to check the solder
joints. Then each individual stocking of the slide can be tested for leakage in its own sleeve, testing the tuning slide as the first sec- tion of the horn. There is no particular order for testing the rest of the instrument.
Repairing Leaky Valves
The repair of leaky valves entails plating of the valve to a point where the valve is too
tight to fit the casing, after which, the valve is ground to a perfect fit in its own casing. This is the procedure to follow:
1. If the valve has a nickle plating on it, it must have the plating removed, as described in the article on removing of plating. (Stripping) 2. Copper plating is used to build the
valve up to a point where the valve will fit in the casing from the bottom 14 of its own length. (See article on Plating.)
3. The valve is then ground lightly as in the valve block to remove any high spots on the plated surface. (See article on use of Valve Block.)
4. The casing is lapped out with the casing lap to remove any imperfections.
5. Clean out the casing thoroughly. 6. Solder a brass rod in the bottom of the valve. This rod should be a smooth fit in the inside wall of the valve. Be certain that the- solder does not extend above the valve. 7. Place the brass rod in the vise firmly. 8. Apply lanolin to the valve.
9. Gradually work the instrument on the valve with a twisting-turning motion, until the valve will fit tight but smooth through the entire
length of the casing.
10. Add a few grains of fine pumice to the lanolin and repeat the procedure as outlined in the previous step.
11. Remove the lanolin and replace the same with No. 10 motor oil and a few grains of pumice. Repeat the procedure as outlined in step No. 9.
12. When the valve feels free enough to be able to continue this procedure by hand, unsolder the brass bar, replace the valve stem and button, tie a piece of twine about the valve button and wrapping the twine around your hand to complete the grinding procedure. This grinding should continue until the valve feels smooth and firm yet with a free motion in the casing. Rather than over-grind a valve, it is wise to clean off the valve and wipe out the casing and try the valve once or twice. If the valve still requires more grinding, the past pro- cedures can be repeated. When the grinding of the valve is completed, it is wise to apply a nickel flash plating to the valve since the hard surface of nickel plating will give a better bear- ing surface against the soft brass wall of the valve casing. (See article on nickel plating.) All screw type valve guides must be removed prior to plating of the valve. Replacement of valve guides on valve plating jobs is definitely recommended.
Repairing Leaky Slides
If the slides of a brass instrument are worn to a point of leakage, they can be repaired by building the slides up with plating and grinding the slides to fit. They may also be stretched slightly and refitted in their
respective outside sleeves. Stretching of these slides can be accomplished by either burnish- ing the slide while it is on a smooth fitting mandrel or by striking light blows against the slide with a dent hammer while the slide is on the same type mandrel. If the stretching is done by the hammering method, it is impor- tant to remember that the hammer marks must be kept smooth, light and even. After the slides have been stretched, the slide should be ground to fit smoothly.
Tempering Brass and Steel Brass
Brass is one of the base metals used by repairmen that fall into the soft or malleable category, that is to say that it can easily be
worked with. Temper in any metal is descrip- tive of the tensile strength or hardness of the material. When brass is purchased from the mill, it may come in any degree of temper desired. When there is a complete absence of temper to the brass, it is referred to as “dead soft.” The other points of temper in the materi- al are: medium soft, soft, medium, half hard and hard drawn. The highest degree of tem- per in brass is sometimes referred to as spring temper. Temper is added to brass by actually working on the material. This can be done by burnishing, hammering, stretching, shrinking, bending or drawing and spinning. For this reason, some dents cause the mate- rial to become too tempered for easy removal. To bring brass back from a high degree of temper to its malleable or workable state, it is sometimes necessary to anneal the brass. This softening process, known as annealing, is performed by heating the brass on a soft flame till it is red hot, then either let it cool slowly or chill it suddenly by immersion in cold water. Sudden immersion will not affect the state of the material. If a dent is in the form of a crease, annealing of the metal will have a tendency to lessen the chances of the materi- al cracking.
Steel
Unlike brass, temper cannot be added to steel in a gradual fashion. It can only be added suddenly. Temper can gradually be removed from steel. To properly understand the process involved, it is necessary to segre- gate the types of steel. For the most part, the steel used by repairmen falls into two cate- gories, namely, carbon steel and high speed tungsten. Since the tools made by the aver- age repairman are made of drill rod which is carbon steel, we shall confine the discussion of the tempering and drawing of temper to the carbon steel. When steel is purchased from the mills, it comes in a malleable or workable state. We can soften this steel further by applying heat. When steel is red hot, it
becomes medium soft. When steel is yellow or orange hot, it is dead soft. Molten steel is referred to as white hot. Sudden chilling of red, orange or yellow steel will cause the mol- ecules of the steel to freeze causing the steel