Week 16- Brass Tubing

I was fortunate enough to work with my instructor John Huth on an additional project in which I created a brass tube and drew it to a specific diameter (an inner tube for a 1925 Besson Meha vintage trumpet).  

The first step was to anneal a flat piece of stock brass.  Following the annealing process, I placed the stock in muriatic acid to remove the heat varnish on the metal.

I hammered the brass around a trombone slide mandrel.  The size would vary depending on the size of tube that you were intending to draw.  The idea is to find a mandrel that is closest to the diameter of the tube to ease in the hammering process.  The seam created in this process is the traditional way that Besson tubes were created.  While seamless tubes are used now, in restoring an instrument to its original state, the edges of the brass tube need to be 'butted' together with no overlap.

Covering the butted seam with heat resistant flux, I was ready to solder.  In this instance we used brass braising wire.  The idea is to get the brass almost to a melting temperature so the piece and the wire heat as one after the initial braising.  Be sure to clean the braising wire and the seam of the tubing with sand paper and a small poker before braising.  Using super heat resistant flux is also recommended.

Above, I am heat the brass before applying the braising wire to the part.  The hot red color is definitely the best climate in which the braising wire can flow into the seam.  I had some trouble with the seam widening with heat.  I had to repeat the hammering process for the lower half of my tube and repickle the metal before repeating the braising process on the lower half of the tube.  However, the end result was reasonable.  I filed and sanded the tube so that it would draw evenly through the die we had place on the machine.  While I wasn't able to capture video footage of drawing the tube, the end result is shown below.  

The process really opened my eyes to how creative I can be in completed and repairing a damaged instrument.  Not only can I fix an existing part, but I can actually manufacture parts that I can use to restore vintage instruments.  I'm sure the applications of the project will be helpful in many other aspects of repair.