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How to Remove Dents from Brass Instruments

A brass instrument in need of some repair
Northport High School Tiger Marching Band

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. Many players seek out expert repairers certified by the National Association of Professional Band Instrument Repair Technicians, Inc. (NAPBIRT), but an equal number 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. In this article, you'll learn how to remove dents to the bell and tubing of brass instruments.

A brass instrument in need of some repair
Northport High School Tiger Marching Band

Things You'll Need:

  • Valve Grease And Oil
  • Dent Burnisher
  • Tapered Dent Rolling Tool For Your Individual Instrument (These Are Widely Available For Trumpet, Trombone, And French Horn)
  • Fixed Dent Rods With Vise (Available In Sizes For All Brass Instruments)
  • Expandable Valve Casing Mandrel
  • Flexible Dent Rods

Disassemble and clean the instrument thoroughly.

A collection of dent rods and dent balls

Oil the fixed dent rod heavily. Clamp the vise to a table or workbench. Slide the dented tube or bell over the 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.

Rolling out dents on a tuba's bell

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.


  • 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.


  • For breaks and dents that close tubes completely or almost completely, consult a professional repair person.
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