How a Trumpet is Made
Manufacturing the mouth pipe
The general procedure is the same as for the bell
A steel core bar with precise dimensions is inserted into the pipe (as in the bell manufacturing process), which is then drawn through a close-fitting exterior die. This results in a high-precision pipe with dimensions that are accurate to the micron level.
The pipe is filled with a soft, easily melted metal or similar substance to prevent it from losing its rounded shape. A form is then used to bend the pipe to the desired shape. Finally, the metal inside the tube is melted and poured out.
A steel ball with the same diameter as the inner diameter of the curved pipe (11 mm-12 mm) is passed through the pipe to precisely shape its inner diameter.