That 8 pound hammer ball bearing.

I heard a while back about development success in repairing dents in musical instruments, particularly larger ones like sousaphones that have to be thinner brass due to the large size. Apparently school systems with a lot of instruments, dented by parades and halftime shows spend thousands annually to have dents removed, or replacement instruments dented beyond economic repair. Traditionally. repair techs have developed special hammers and tools and sand bags and all kinds of methods involving taking horns apart to fix, a very artistic and skill-intensive, time consuming process. Well somebody found using special "Rare Earth" electromagnets and huge dense ball bearings work quickly and smoothly!

Regular magnets won't work. These magnets are STRONG. Way beyond anything normal. Warnings say to keep knives and tools 10 feet away for fear they will fly through the air, not stopping for body parts in the way. (Make a visual image of that!) The ball is selected for best size, and from the inside, rolls along at enormous pressure and simply irons out the dents! Doesn't fatigue the metal much, either, like hammering out would, so a horn can be repaired more times without ruin. The kit costs about $900, so isn't for casual buying, but a few repairs could make up for that in schools, shops or the like.