Over the course of time, many brass instruments will acquire small dents and dings. These changes to the body of the instrument can cause changes in pitch stability, tone and general playability. Some musicians take courses in band instrument repair or simply learn to do basic repairs on their own. Some repairs, such as piston honing, must be done on special professional equipment, but many dents can be removed at home with standard repair equipment.
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Things you need
- Fixed dent rods with vice (available in sizes for all brass instruments)
- Tapered dent rolling tool for your individual instrument (these are widely available for trumpet, trombone, and French horn)
- Dent burnisher
- Expandable valve casing mandrel
- Flexible dent rods
- Valve grease and oil
Disassemble and clean the instrument thoroughly.
Oil the fixed dent rod heavily. Clamp the vice to a table or workbench. Slide the dented tube or bell over the dent rod. Push the dent ball at the end of the rod against the dent(s) in the instrument. Push slowly and carefully; don't stretch the metal out. Remove slowly. Use the dent burnisher to smooth out any remaining small dents in the area. Move the burnisher quickly and lightly over dented areas, much as you would with a shoe brush over the toe of a shoe.
Insert the tapered dent rolling tool into a heavily dented bell. With steady pressure, roll the bell around the tapered dent rolling tool to even out the bell's dent(s). Do not push the metal out farther than it would be normally; stretching the metal weakens it. Use the dent burnisher to smooth out any remaining dents or dimples and unevenness.
Oil the expandable valve casing mandrel and insert it into the dented valve. Apply steady pressure to push the dent(s) out of the valve. Remove the mandrel.
Remove dents in long pieces of tubing with flexible dent rods. Oil the dent ball and insert it slowly into the tubing. Push the dent ball slowly through the entire tube, pressing it against the dented areas to push out the dent. As with other tools, be careful not to let the flexible dent rod push the metal beyond its original dimensions.
Clean any parts that have been repaired and reassemble the instrument.
Tips and warnings
- Always use the right tool for the dent. Never use a larger dent ball than necessary.
- Insert tools into instruments slowly and carefully.
- Avoid stretching the metal.