Over time, brass instruments tend to acquire dents, which can change the shape of its body, and its pitch or tone. With standard repair equipment, you can repair a dented brass instrument easily at home.


Basic repairs are simple to do, but some repairs like piston positioning must be done professionally. In this article, you will learn how to straighten a dent of brass instruments.


Things you will need


  • Fixed dent rod (that has a vise)
  • Dent burnisher
  • Tapered dent rolling tool (designed for your instrument – like a trumpet, horn, or trombone)
  • Valve casing mandrel that expands
  • Valve grease/oil
  • Flexible dent rods



  1. Dissemble your instrument.


  1. Clean the parts thoroughly so that all dust particles are removed.


  1. Now, oil the fixed dent rod deeply. Clamping the vise on a table, insert the dented tube over the dent rod. You will have to push the dented ball slowly up to the end of the rod, while going against the dent you want fixed in the instrument. Then remove it slowly. Keep your hand slow and stead as you do this so that your instrument is not scratched.


  1. With the dent burnisher, smoothen the small dents. You can move the burnisher quickly over these dents.


  1. Then, insert the tapered dent rolling tool in the bell, which is heavily dented. Keeping a steady amount of pressure, use the bell to roll around the tapered denting tool. This will flatten the dents.


  1. Use the dent burnisher again to smoothen and dents that remain.


  1. Oil the valve casing mandrel and then insert it in the valve with a steady pressure. This will push out the dents from the valve. Now remove the mandrel.


  1. With the flexible dent rods, remove any dents in the long pieces. Oil the dent ball so that it can be easily inserted into the tubing, and the dents be removed from here. Place steady pressure so that the instrument’s dimensions aren’t altered.