Thread: dent removal in brass

Or... Drill a 1mm hole in the centre of the dent, thread a motorbike cable or similar through, silver solder on a curved steel plate (shaped/domed to match the undented section) to the cable, and give it a pull. Maybe a bit of heat? -But you don't want to stretch the metal eh? Cut and remove the cable & plate, fill the hole with silver solder. Polish.
Works with motorbike tanks.

Originally Posted by joolstacho

Or... Drill a 1mm hole in the centre of the dent, thread a motorbike cable or similar through, silver solder on a curved steel plate (shaped/domed to match the undented section) to the cable, and give it a pull. Maybe a bit of heat? -But you don't want to stretch the metal eh? Cut and remove the cable & plate, fill the hole with silver solder. Polish.
Works with motorbike tanks.

Thanks for your idea joolstacho. I had thought about your idea before as it happens (honest). But I wondered about filling the holes after doing the actual dent removal. There are about six or seven dents in all, close together right around the curve of the tuning slide and a bigger one eight inches from the bell. I can see it would work providing I use wet cloths as a heat sink each side of the brazing to prevent melting the soft solder which the trombone's joints are made of. But there isn't enough space to put these cloths between the holes on the tuning slide. Do you think the heat from a hole that is being brazed would melt the brazed hole(s) next to it?

Brazing would definitely melt soft solder in the vicinity!
Why not soft solder some brass wire pins to the dent and tug on those until you have the dent where you want it? It might take several lots of wire pins in different places to get a feel of how the metal moves. Once done, the remaining solder should scrape or sand and polish off back to the brass.
If you have a look in YouTube for "Using a Stud Welder to Repair Dents". That's the same principle and you might get some idea of how the sheetmetal might respond.

Ah right, I hadn't imagined a group of dents close together and also to a solder joint.
Tricky little job. A little blob of soft solder would cover the 1mm hole. But also Low melting point silver solder is available.
You can even get it in little syringes already mixed with a flux. You'd need a fine closely focused flame. There's a special coating you can paint on which 'localises' the heat too.
Can you post a photo?

I reckon the place to start is a large steel ball (bearing?) on a string, as big as will fit, and attempt to locate it behind the dent and move it around, firmly, so it acts like a dolly. Perhaps gently tapping the edges of the dent.
The difficulty I see is the foresee is that the Tubing is likely to be workhardened, and need annealing to make it workable.

But Russ, how do you get the ball back past the dent "attempt to locate it behind the dent" so you can draw it out? Or do you start with smaller balls, working your way up.
That's the sure way of work-hardening the brass eh? And tapping around will just stretch the metal. Not what we need.

Originally Posted by joolstacho

Ah right, I hadn't imagined a group of dents close together and also to a solder joint.
Tricky little job. A little blob of soft solder would cover the 1mm hole. But also Low melting point silver solder is available.
You can even get it in little syringes already mixed with a flux. You'd need a fine closely focused flame. There's a special coating you can paint on which 'localises' the heat too.
Can you post a photo?

Thanks for the ideas. I will take a photo when my granddaughter comes round next time. I don't have a phone with a camera so she will use her's.

Originally Posted by russ57

I reckon the place to start is a large steel ball (bearing?) on a string, as big as will fit, and attempt to locate it behind the dent and move it around, firmly, so it acts like a dolly. Perhaps gently tapping the edges of the dent.
The difficulty I see is the foresee is that the Tubing is likely to be workhardened, and need annealing to make it workable.

How would you attach a ball to a string? I suppose you could drill a hole through it and tie a know in the other side of the string. I've answered my own question!

Hi Wooly, Guys,

This thread really belongs in metalwork general, but not to worry !

You will have to anneal the steel ball before you can drill a hole in it, unless you can get a soft one. But drilling one that is the right size and pulling it through the tube bore with a string is a workable idea !

Put the ball in the middle of the string and thread it right through the instrument.
Can a trombone be disassembled at all?

Originally Posted by BaronJ

Hi Wooly, Guys,

This thread really belongs in metalwork general, but not to worry !

You will have to anneal the steel ball before you can drill a hole in it, unless you can get a soft one. But drilling one that is the right size and pulling it through the tube bore with a string is a workable idea !

Hi BaronJ. About getting soft steel balls, yes I have seen them advertised on the net but I'm not sure what sizes yet. I'm doing an experiment with a 10 mm ball to see how that goes first.

Originally Posted by russ57

Put the ball in the middle of the string and thread it right through the instrument.
Can a trombone be disassembled at all?

Hi Russ57. Disassemble a trombone? Yes to a degree. The sliders undo from the tuning crook-and-bell tubes and the sliders come apart from each other. Those are the main parts but the tuning crook separates from the bell tube and the mouthpiece comes out too. If you really want to unsolder various joints then the whole trombone will come to pieces. But the bell and about 24 inches of tube behind it are all made in one piece. About putting the ball in the middle of the string and threading it so you can then pull it both ways, yes of course. I should have known.

Hi Guys. While I was thinking through all the ideas you have sent, I noticed that the water drain operating lever, called a water key, wobbles so much that the felt sealing pad on its end sometimes misses the nozzle and therefore fails to seal the trombone tube. When left like this the trombone doesn't play very good and you have to fiddle with the water key to get it to seal. If you're at home, messing about with the 'bone this doesn't matter but if you're on stage it can mess up your entry to the music and make you start late or at least to miss a few bars. So I started to investigate why the key wobbles and found that the hole in the brass water key had worn very much oversize. Then, instead of filling the hole with epoxy resin and drilling it out to the correct size, a quick fix, I tried to force a bush into it. Guess what happened. Yes, the water key split in two. so now I am distracted from removing dents to fixing the water key. So I won't be writing about dent removal for a while.

Originally Posted by woolyhead

Hi Guys. While I was thinking through all the ideas you have sent, I noticed that the water drain operating lever, called a water key, wobbles so much that the felt sealing pad on its end sometimes misses the nozzle and therefore fails to seal the trombone tube. When left like this the trombone doesn't play very good and you have to fiddle with the water key to get it to seal. If you're at home, messing about with the 'bone this doesn't matter but if you're on stage it can mess up your entry to the music and make you start late or at least to miss a few bars. So I started to investigate why the key wobbles and found that the hole in the brass water key had worn very much oversize. Then, instead of filling the hole with epoxy resin and drilling it out to the correct size, a quick fix, I tried to force a bush into it. Guess what happened. Yes, the water key split in two. so now I am distracted from removing dents to fixing the water key. So I won't be writing about dent removal for a while.

Well that was quick. Here I am again. Hopefully my pictures are attached.

Hi Wooly,

Can you solder a pair of small brass washers to the inside of the lever ?