dent removal in brass

[woolyhead]

How could I remove small dents (the biggest is 20mm long x 3mm deep, the others are roughly circular about 6mm diameter and 2mm deep) in a brass trombone tube? Most of these dents are halfway round the curve of the tuning slide and the biggest one is in the bell. Musical instrument repairers charge dearly for doing this work so how could I do it myself? What they do is to roll a rounded steel ball over the inside of the dent and gradually increase the sizes of the balls. These tools are also expensive. Could anyone suggest a different way to do the job?

[Grahame Collins]

Hi Woolyhead

Welcome to the MetalWork Forums

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Hopefully someone who knows more than I about trombone repair will be along in due course.

Welcome

Grahame

[BaronJ]

How could I remove small dents (the biggest is 20mm long x 3mm deep, the others are roughly circular about 6mm diameter and 2mm deep) in a brass trombone tube? Most of these dents are halfway round the curve of the tuning slide and the biggest one is in the bell. Musical instrument repairers charge dearly for doing this work so how could I do it myself? What they do is to roll a rounded steel ball over the inside of the dent and gradually increase the sizes of the balls. These tools are also expensive. Could anyone suggest a different way to do the job?

Hi Wooly,

Welcome to the forum. I've been here a while, nice set of guys.

As far as your trombone dents are concerned, you can buy steel balls, whether you can get the size that you need could be a problem. The last time I saw anything like that the steel balls were pushed through the tube hydraulically.

[russ57]

Hit you tube.
I've had instrument repair pop up in my feed. Looks like diy is doable with a bit of bravery.

I think the biggest question is what is at risk. Is it a valuable item, what would the consequences of messing it up be, are you wanting to just make it better /more playable, or do it up for sale...

[woolyhead]

Hit you tube.
I've had instrument repair pop up in my feed. Looks like diy is doable with a bit of bravery.

I think the biggest question is what is at risk. Is it a valuable item, what would the consequences of messing it up be, are you wanting to just make it better /more playable, or do it up for sale...
This trombone is not a very valuable item. About 50 pounds sterling. The consequences of messing the job up are not very much. I just want to make it look better for my own satisfaction really and see whether it sounds better.

[woolyhead]

Hi Wooly,

Welcome to the forum. I've been here a while, nice set of guys.

As far as your trombone dents are concerned, you can buy steel balls, whether you can get the size that you need could be a problem. The last time I saw anything like that the steel balls were pushed through the tube hydraulically.

And the ones I've seen advertised are expensive. But on the net I found this idea (diagram attached). The idea is to thump the hammer head into the stop so that vibrations travel down to the magnet and make it vibrate strongly. The claim is that the ball then vibrates and thereby hammers the dent out. But the magnet has to be very powerful to make it work. But at least the ball doesn't have to be the exact size. Anyway I can't try this idea out because I haven't got access to a powerful magnet.

[BaronJ]

And the ones I've seen advertised are expensive. But on the net I found this idea (diagram attached). The idea is to thump the hammer head into the stop so that vibrations travel down to the magnet and make it vibrate strongly. The claim is that the ball then vibrates and thereby hammers the dent out. But the magnet has to be very powerful to make it work. But at least the ball doesn't have to be the exact size. Anyway I can't try this idea out because I haven't got access to a powerful magnet.

Hi Wooly,

That idea is a new one on me ! It should work in theory. As far as the magnet is concerned, a dead hard disc drive out of a computer will provide you with a really strong magnet. I have several kicking about that I use for various jobs.

[woolyhead]

Hi Wooly,

That idea is a new one on me ! It should work in theory. As far as the magnet is concerned, a dead hard disc drive out of a computer will provide you with a really strong magnet. I have several kicking about that I use for various jobs.

I didn't know computer disc drives had powerful magnets in them. That's useful information. Thanks very much BaronJ. Now I can find myself an old computer disc drive and try the vibrating ball idea out. If this works it will cost a whole lot less than a set of steel balls of the right sizes. Great news. Thanks again.

[BaronJ]

Hi Wooly,

Extracting the magnets from a hard disc drive is not difficult ! But do watch your fingers, they bite, they don't take prisoners.

The magnets are part of the head drive motor, there is one magnet on each side of the head drive coil. The bearings are useful as well ! The actual platter spin motor is a three phase one and not much good for anything, I throw the ones that I remove into the scrap metal bin, though I've heard that some people melt them down for the scrap alloy. The alloy frame often gets melted down as well.

The platters make good first surface mirrors and very good reference flats, but they do scratch very easily, they are often alloy as well but there as some glass ones knocking about. They are usually the 3 inch ones.

If you can lay your hands on an old 5 inch drive the magnets in those are big, very big and very strong.

Good luck. :)

[woolyhead]

Hi Wooly,

Extracting the magnets from a hard disc drive is not difficult ! But do watch your fingers, they bite, they don't take prisoners.

The magnets are part of the head drive motor, there is one magnet on each side of the head drive coil. The bearings are useful as well ! The actual platter spin motor is a three phase one and not much good for anything, I throw the ones that I remove into the scrap metal bin, though I've heard that some people melt them down for the scrap alloy. The alloy frame often gets melted down as well.

The platters make good first surface mirrors and very good reference flats, but they do scratch very easily, they are often alloy as well but there as some glass ones knocking about. They are usually the 3 inch ones.

If you can lay your hands on an old 5 inch drive the magnets in those are big, very big and very strong.

Good luck. :)
That's also useful to me. Obliged. But I did wonder whether the small ball in the tube might dent the original dent the opposite way over a small part of it and not actually remove it. I know that musical instrument repairers roll their balls (!) or slide them from side to side right across the dent and thereby avoid what I fear for what the small ball might do as it hammers straight down on to it. Not that it matters much because a rolling action would smoothe it out at a later stage anyhow. What would you think?

[BaronJ]

Hi Wooly,

As I said earlier the magnet and steel ball method is something I've not seen before ! :no:

The passing of a steel ball down the tube to force out a dent or crease is the only one that I know of.

I would have thought that an electro magnet with a shaped anvil with the steel ball inside the tube would be more effective because the electro magnet could be driven with a varying frequency voltage. That would have the effect of a small vibrating hammer and would provide greater control of impact level.

Beyond that, I don't know. If you know any instrument makers they would be the people to ask.

[woolyhead]

Hi Wooly,

As I said earlier the magnet and steel ball method is something I've not seen before ! :no:

The passing of a steel ball down the tube to force out a dent or crease is the only one that I know of.

I would have thought that an electro magnet with a shaped anvil with the steel ball inside the tube would be more effective because the electro magnet could be driven with a varying frequency voltage. That would have the effect of a small vibrating hammer and would provide greater control of impact level.

Beyond that, I don't know. If you know any instrument makers they would be the people to ask.

Yes, you're right BaronJ, on several scores. An electromagnet sounds good but an anvil would have to curve in two directions at the same time. Still. it could be done. But I'll try the disc drive magnet first once I've located a disc drive. I used to have three computers in the shed but we recently took them to a dump so I'm asking around, Someone will have one I'm sure. The trombone was made in 1870 in Paris France by a firm who has now ceased to exist but present day brass instrument makers would know how to remove dents, although their idea of what's inexpensive wouldn't be the same as mine. I'll let you know how I get on. Nice talking with you.

[BaronJ]

Hi Wooly,

I've been having a think about this based on my previous post ! Dangerous I know :U

A steel ball would only be a point contact, so any anvil would not need to follow a curve but would need to have a radius to match the tube and would not need to be very long, only about the diameter of the steel ball. If the anvil were part of the piston in a solenoid the ball could be made to vibrate in sympathy with the magnetic field created by the varying current in the solenoid coil. A bit like a tattooists needle.

[woolyhead]

Hi Wooly,

I've been having a think about this based on my previous post ! Dangerous I know :U

A steel ball would only be a point contact, so any anvil would not need to follow a curve but would need to have a radius to match the tube and would not need to be very long, only about the diameter of the steel ball. If the anvil were part of the piston in a solenoid the ball could be made to vibrate in sympathy with the magnetic field created by the varying current in the solenoid coil. A bit like a tattooists needle.

Yes I suppose so but with a ball diameter of, say, 20mm, the increase in diameter of the trombone's bell (where the dent is located) would be about 15mm. So under a flat anvil, this side of where the ball strikes the other side of the brass, there would be an air gap of about 5mm on one edge of the anvil if it was held perpendicular to the centre line (axis) of the bell. But I suppose I could hold a flat anvil at some other angle so as to minimise the air gap. So when the ball strikes the inside of the bell, the brass where it strikes could balloon out a bit into this air gap. Providing the extent were not too much that wouldn't matter and it could be gently tapped back into place using a small hammer. Brass instrument repairers use some sort of fibre hammer for that. Yes it all sounds good, Thanks for the ideas. https://metalworkforums.com/images/icons/icon7.png

[jhovel]

I wonder if you could not use a VERY powerful electromagnet (not difficult to make) and use a variable power supply that lets you control the force of the ball to directly push the dents out. A bit like the "paintless dent removers" do manually (look at Youtube to see how that works - fascinating to watch!). I'm thinking of a magnet that can lift 100kg or more. Since the ball inside the tube is only close to the magnet face in one spot, and the rest of it further away, you should be able to move it about the dent slowly but forcefully enough to roll and push it out in a very controlled fashion.
I might experiment a bit with that idea to get dents out of steel motorbike tanks and the like. Might take a stronger magnet, but that's not too tricky....
I might start with the secondary coil and part of the core of a microwave transformer I have.... Let's see what sort of force that can generate, at controlled DC input up to where it gets hot..... Vibrating it with square wave pulsed DC might even be more forceful.....
Anyone else got any good ideas for sourcing a very strong electromagnet without winding one from scratch?

[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.

[woolyhead]

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?

[jhovel]

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.

[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?

[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.

[joolstacho]

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.

[woolyhead]

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.

[woolyhead]

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!

[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 !

[russ57]

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

[woolyhead]

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.

[woolyhead]

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.

[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.

[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.

[BaronJ]

Hi Wooly,

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

[woolyhead]

Hi Wooly,

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

Hi Baron. Yes I could solder these washers but why would I? The gap between the lever and the posts was meant to accomodate the spring. Unless I use a spring which mounts somewhere else. Actually I prefer that solution in which case you are right about using washers. Presumably to prevent the key from wobbling? Actually soldering is a bit of a risk because the cap on the end of the lever is soft soldered and I'd have to use a wet cloth to prevent it falling off. But the washers could be done using solder although I'm finding epoxy resin is much easier.
Looking at the download of my previous post I see the photos of the trombone before and after the dents were removed didn't get sent. I'll try again, Right this is my problem in sending trombone photos. They arrived by e mail and I can't find a way to link them to this post on the forum. They have a reference number img1688.jpg in the e mail section but how do I refer to it in the forum attachments?

[BaronJ]

Hi Wooly,

I don't think that a pair of washers would impact the spring at all, indeed if you didn't want to solder them a dab of super glue would do the same and could be removed if needed with a little heat.

I've just been looking at the drawing you posted. Is the key solid or folded ? Is the 2 mm you called out a gap or is it a solid piece. Good pictures would make understanding what you can see a lot easier. :)

I was looking at a cornet and the spring on the little lever was quite small looking like a pair of chopsticks with a loop of wire at the end. Your drawing seems to show a much more complicated spring, probably to reduce the side twisting of a hairpin spring.

As far as pictures in an Email simply copy them to the desktop or somewhere you can find them, then go to "Manage Attachments" below the post, click on "Add Files" then click on "Browse" which will open a window on your machine, navigate to the pictures you want to post and click on it. Then click on "Upload", Insert, then "Done".

HTH.

[woolyhead]

Hi Wooly,

I don't think that a pair of washers would impact the spring at all, indeed if you didn't want to solder them a dab of super glue would do the same and could be removed if needed with a little heat.

I've just been looking at the drawing you posted. Is the key solid or folded ? Is the 2 mm you called out a gap or is it a solid piece. Good pictures would make understanding what you can see a lot easier. :)

I was looking at a cornet and the spring on the little lever was quite small looking like a pair of chopsticks with a loop of wire at the end. Your drawing seems to show a much more complicated spring, probably to reduce the side twisting of a hairpin spring.

As far as pictures in an Email simply copy them to the desktop or somewhere you can find them, then go to "Manage Attachments" below the post, click on "Add Files" then click on "Browse" which will open a window on your machine, navigate to the pictures you want to post and click on it. Then click on "Upload", Insert, then "Done".

HTH.
Much obliged BaronJ. I'll give it a go soon. Meanwhile the key is solid and the 2mmis also solid. If the washers don't impact on the spring they would have to be smaller in diameter than the coils of the spring. But what would be the purpose of using these washers? With the original maker's springs there was barely enough room to get them in. I'll send the trombone pictures soon. Sorry about the quality of my hand drawn sketches but this object is difficult to draw right. I have moved the photo to documents where it is called scan0008 but I can't seem to pick it up for adding to my forum post. Still working on it.

[BaronJ]

Hi Wooly,

Thanks for the extra bit of info, I originally got the impression that the key was a folded part, that was why I suggested small washers.

I look forward to the pictures.

[woolyhead]

Much obliged BaronJ. I'll give it a go soon. Meanwhile the key is solid and the 2mmis also solid. If the washers don't impact on the spring they would have to be smaller in diameter than the coils of the spring. But what would be the purpose of using these washers? With the original maker's springs there was barely enough room to get them in. I'll send the trombone pictures soon. Sorry about the quality of my hand drawn sketches but this object is difficult to draw right. I have moved the photo to documents where it is called scan0008 but I can't seem to pick it up for adding to my forum post. Still working on it.<br>
<br>

[woolyhead]

<br>
<br>
The attached is my trombone after I removed some of the dents. I used 11mm steel balls for removing those dents lying in curves and an 18 inch by 3/4 inch steel rod for straightening out the big dent which was 7 inches from the bell. I put one end of the rod in the bench vice, very tight and made a wooden jig going down to the floor to hold it even more steady with the rod inserted into the bell end. I then had two hands free for gripping the trombone and pushing the dented part down onto the rod. The jig prevented the rod from moving down towards the floor. Where the brass tubing is creased it takes a lot of force to push it out. I was surprised how clean and even the outside of the trombone looked after doing this work on it. Very pleased. The quality of the photograph isn't very good but at the extreme left hand side you can just make out the two little posts each with a ball on top which are part of the water key assembly. This trombone is very old, probably about 140 years and some of its construction is quaint.

[woolyhead]

Hi Wooly,

Can you solder a pair of small brass washers to the inside of the lever ?
That's a good idea Baron. It would save having to fill the big hole worn in the water key while providing a support for the sleeve that goes through the key and touches the support posts. I know that everyone wanted a picture of the water key assembly but my sketches are a bit difficult to decypher at the moment. I had another idea about how to remove dents from the trombone tube 7 inches away from the bell. Point 1: the force required is outward, at right angles to the sac but's axis. Point 2: to generate this force requires the input force to be virtually along the axis of the tubing ie down the trombone's throat. What device does this? A car jack of course. But the internal width (dia) of the tube at this 7 inch point is only 30mm so it would have to be a very small car jack. I considered using a hydraulic or pneumatic ram for this but I couldn't buy anything small enough. So what about using a nut and bolt? The expansion is outward as required and the input is down the throat of the trombone using spanners on the hexagon head of the bolt and the nut. There isn't much room for turning the hexagons when inside the 30mm space but I reckon it could be possible, After all, the expansion of the nut and bolt assembly only needs to be 2 to 3 mm, the depth of the dent. Another idea that came to mind is the use of a worm thread whose axis lies parallel to the main trombone tube's axis. The worm could be made to push its mating screw outward. But the nut and bolt is simpler. I have already removed the big dent in my slush pump as I described elsewhere on this forum so I'm keeping the nut and bolt idea in my pocket for another time. In case anyone didn't know, a sac but and a slush pump are alternative names for a trombone.

[woolyhead]

And the ones I've seen advertised are expensive. But on the net I found this idea (diagram attached). The idea is to thump the hammer head into the stop so that vibrations travel down to the magnet and make it vibrate strongly. The claim is that the ball then vibrates and thereby hammers the dent out. But the magnet has to be very powerful to make it work. But at least the ball doesn't have to be the exact size. Anyway I can't try this idea out because I haven't got access to a powerful magnet.

For dents closer to the trombone's bell the idea is not to hammer on the dent but to press the brass back into place. I did this with what amounts to being an anvil and a press but the anvil took a bit of making and I've hit on a simpler method. Lay a nut and bolt from side to side with the bolt head resting on the dent and the nut resting on a load spreader right opposite. Then unscrew the nut (or the bolt) and as the nut and bolt assembly expands it presses the dents out. What do we think of that idea?

[BaronJ]

Hi Woolyhead,

You would have more control with a scissor type device that expanded as you squeezed the handles !

[russ57]

This popped up following a link from my wife..

https://youtu.be/EuDeI3SNDWg
(the whole series is interesting)

[woolyhead]

Hi Woolyhead,

You would have more control with a scissor type device that expanded as you squeezed the handles !

Yes I understand what you say Baron J. It takes quite a lot of pressure on a dent to push it back where the brass belongs. One of my ideas was to place a nut and bolt at right angles across the trombone tube and unscrew it. But unscrewing needs a spanner, or so I thought, and a spanner could foul on the side of the tube, as I discovered. So I thought of using a nut with a disc attached, the disc to have a string of holes right round near its edge and two thin rods which remain central, along the axis of the tube and which hook into the holes in the disc. Then one rod is pushed while the other, which is diametrically opposite, is pulled, thus rotating the disc and unscrewing the nut. When the maximum rotation is achieved the rods are unhooked and moved round to the next suitable pair of holes and further rotation becomes possible. In my trombone the tube diameter was30 mm so the disc could be 28mm to allow clearance. With a 13mm nut the dia of the ring of holes could be on a 19mm pc dia allowing 2.5mm thickness for the rods and adequate space between push-rod hole and edge of the disc. In that case the mechanical advantage of the push-rod over the end of the bolt is 3.14x19 / 1.25 = 60 /1.25 = 48. 1.25 is the thread pitch on an M8 thread. I may have made small errors in this calculation but it's approx correct. I could increase the mechanical advantage by a factor of at least 10 if necessary. I could draw this and sent it as an attachment if I could remember how.

[BaronJ]

Hello Woolyhead,

Actually if you watch the video, the old guy has the perfect tool to remove dents even in very small diameter tubes. A hundreds of years old idea and so obvious its brilliant ! One that I will certainly be noting for future use.

[woolyhead]

Hello Woolyhead,

Actually if you watch the video, the old guy has the perfect tool to remove dents even in very small diameter tubes. A hundreds of years old idea and so obvious its brilliant ! One that I will certainly be noting for future use.

He seems to support the dent inside the sax tube using a rod whose other end is held in a vice. My question is that if he hammers down on to the outside of the tube ie in the same direction as the dent goes, how does that push the dent out, ie in the opposite direction?

[BaronJ]

He seems to support the dent inside the sax tube using a rod whose other end is held in a vice. My question is that if he hammers down on to the outside of the tube ie in the same direction as the dent goes, how does that push the dent out, ie in the opposite direction?

Hi Woolyhead,

If you watch closely he doesn't hammer the dent from the outside at all !

He taps the steel rod that has the curved end placed inside the tube, so that the rod vibrates and gently pushes out the dent. Basically a miniature hammer inside a very narrow tube.

Absolutely brilliant !

The skill would be knowing how hard to vibrate the rod and exactly where where to place the curved end.

[woolyhead]

Hello Woolyhead,

Actually if you watch the video, the old guy has the perfect tool to remove dents even in very small diameter tubes. A hundreds of years old idea and so obvious its brilliant ! One that I will certainly be noting for future use.

Oh yes. I agree, this is brilliant. Thanks for pointing it out BaronJ. It's certainly worth remembering for the future.

[woolyhead]

Oh yes. I agree, this is brilliant. Thanks for pointing it out BaronJ. It's certainly worth remembering for the future.
Actually, I am wondering how thick you reckon the steel rod is and is it mild steel, stainless or spring steel of some sort? I've got a tenor sax with a few dents in it so I may buy a rod of steel and try this technique out for myself. The length looks to me like it's about 300 mm . And the diameter of the rod looks like 8 mm or so. What do you think Baron.J?

[BaronJ]

Actually, I am wondering how thick you reckon the steel rod is and is it mild steel, stainless or spring steel of some sort? I've got a tenor sax with a few dents in it so I may buy a rod of steel and try this technique out for myself. The length looks to me like it's about 300 mm . And the diameter of the rod looks like 8 mm or so. What do you think Baron.J?

From looking at the video the rod looks to be 8 or 10 mm diameter. I wouldn't have thought it to be anything special like spring steel. I agree with you about the length, but I don't think it would be critical, since you could just alter the position where it is clamped.

I did have a play with an 18" inch length of 3/8" rod and tapped it with a hammer handle. The vibration gets more violent the nearer the free end. Get a piece of rod and try it. You might find the creating of the curved end more difficult since you might have to forge it to get the bend properly shaped. But it does twang like a guitar string.