Week 14- Dents, Bell Buckles, Straightening, and Silver Soldering Practice

Week 14 was a whirlwind of dent repair, beginning with stem dents.  It is important to use a mandrel that is closest to the taper of the instrument.  With the mandrel 90 degrees to fluorescent light, direct and acute hand pressure and movement are required to draw out dents.  If you can draw out dents, the integrity of the metal remains.  However, you must be right at the dent in order to avoid blowouts in the brass.  To reach dents further up the bell stem towards the bell bow, the Pratt extension (made at Red Wing) can be used.  Inspection and resetting are key to a quality result.  Additionally, be sure that the mandrel and the instrument are clean.  Any dirt particles or scale can be impressed into the brass with the amount of pressure used in drawing dents!

Crook dents were also covered.  Using our crook dent rod shown above or other dent rods, locking the tool in a vise and lifting the dent is the way to go.  It is important to be careful when doing this. Certain crooks are very vulnerable, as draw knobs can be silver soldered in place.  This creates additional annealing and thus softening of the brass.  Knuckle dents are another repair using dent rods.  Here, using anything with a 90 degree angle to reach into the knuckles between casings is best.  Bracing with the fingers is key here, as any contact with the casing can cause further damage that is much more difficult to fix.

Bell buckles required a bit of prior planning and a lot of work.  The difference between a buckle and a fold in the upper picture is obvious, but in general, any oval shape at the throat is an indication of buckling, not a bell fold.  This is important because the initial work needs to be completed at the sight of the oval.  Therefore, 'roughing out' the bell on a bell forming iron is NEVER the first step.

Beginning by going after the out of roundness and the creases is first.  I began by hammering the large creases flat with a canvas (or rubber) to ensure that the brass did not layer over itself and then tear.  Following this, I traced the creases on a rolling mandrel.  If creases are closer to the rim, changing the angle to behind the bell is sometimes preferable.  Then, I traced any inconsistencies on the outside of the bell, being careful not to roll on the outside of the throat.  Here precision is key, as any over-tracing can cause significant flat spots.

Inspection is an important part of this procedure.  Looking at the inside of the bell and rotating it to look for out-of-roundness, I reformed the shape of the bell until it was as round as possible. Flexing the high sides until the most circular result was reached, I used first the flats of my hands but then had to use an interlocked finger method for more force.

After these steps are taken, then we are sure the throat is no longer the issue of the bell buckle.  From here on out, proceed towards fixing the rim as though it were a bell fold.  Another inspection and fine tuning via burnishing is expected after the roughing out of the bell rim.  The last step is to 'iron' the bell.  Using a bell iron and a rolling mandrel, burnishing the exact point of contact between the brass and the two steel ironing tools will smooth out the last of the inconsistencies.  The bell must keep moving throughout this process or more flat spots will occur.

The "E" Assessment Project is to add additional practice in silver soldering.  Prepping the parts consisted of filling down the brass ends to actively cup he diameter of the longest brass leg.  Setting up the brass rods in a soldering jig at a right angle was harder than it looked.  The soldering process was, too.  It seemed as though the part couldn't get hot enough for the solder to flow.  Following reapplication of flux and a deep breath to center my patience, I was able to solder the first leg of my E project.

Completing Week 14 was straightening bell bows.  On a loose vise, we placed our trumpets on a wooden mandrel and braced at the S brace and tail to 1st slide brace.  Opposing forces ensured that the bell bow would flex in the direction we needed it to.  However, some metals proved to hard to move by hand.  Using the Freshour snap, a belt is looped through the bell bow and used as a lever to 'snap' the bow back into place.  Similar methods of bracing can be used to straighten mouthpipes, however if the mouthpipe is already removed from the instrument, straightening can be completed by hand without a vise.