Brass is a soft metal that is ideal for musical instruments because its composition allows for the resonance of musical notes. Unfortunately, the softness of brass also makes it prone to denting. Removing dents in valuable brass instruments can be an expensive process; however, you can remove dents in the tubing or bell of your brass instrument yourself at home with a few instrument-repair tools.
Take apart your brass instrument only if the dent is unreachable with the instrument intact.
Attach a vice to the workbench. Grip a dent rod with the vice. Thread a dent ball onto the top of the dent rod.
Slip your brass musical instrument's dented tubing over the dent rod and press down to straighten out the dent. Burnish the affected area lightly, just enough to remove any remaining small dents and taking care to not press down too hard on the burnisher.
Remove larger dents in your brass instrument's bell by placing a tapered dent rolling tool inside the bell. Roll the bell around the rolling tool with a steady pressure to straighten the dent out of the metal.
Smooth the outer surface of the bell by gently tapping it with a brass hammer if necessary. Burnish the instrument's bell with a burnisher to remove any hammer marks and smaller dents.
Use a steady pressure when wielding a dent rod, rolling tool or burnisher; too much pressure will cause the metal to stretch irreparably and may later cause cracks and stress fractures. Magnetic dent removers are hard to control and can stretch the brass. The magnets can also break off into sharp pieces that can lodge in the brass instrument tubing, causing a blockage.