Magnetic dent removal

[ghmerrill]

Since my work with my old Buescher Eb is going so well, I decided to remove some of the numerous dents from it. These are all on the outer branches and range from a lot of little almost "pinhole" dings through some larger ones that are perhaps 2" long and about 3/4" wide. Some time ago, following some postings that Dan Schultz (http://thevillagetinker.com/) made in a thread on Tubenet, I acquired some of the material he recommended and these then sat dormant for almost a year. In particular, I got a Neodymium Super Magnet, 1.5 in x 1.5 in (Model ND069-1) from Magnet4less.com (about $47 including shipping) and a 1 7/16" chrome steel bearing ball from Bearingballstore.com ($8 + shipping).

A couple of days ago I started out by trying this approach on an old Martin baritone I got specifically to restore and practice on. I put on a pair of leather gloves (following other recommendations on Tubenet) and placed the magnet in one of those microfiber cloths that are readily available in auto stores, supermarkets, etc. for various kinds of polishing. Dumped the ball down the bell of the baritone and gingerly approached it with the magnet ... CLANK! That sucker is strong. (The best technique is to let the ball settle in some position, then apply the magnet to the horn some distance away and slide it toward where the ball is.) I then proceeded to carefully role out a shallow dent on the outer branch of the baritone. This was a huge success!! I then did several others, to the point that the baritone is now dentless, and with no mishaps. I managed to get the magnet off the horn by twisting it away from the surface and putting it safely in a plastic container, and then in a cardboard box with a very visible warning label attached: "STRONG MAGNET. STAY AWAY. DO NOT APPROACH WITH ANY ELECTRONIC DEVICE." (I am particularly careful about this because my eldest child has an implanted pacemaker and defibrillator, and he really doesn't need for the pacemaker to go into test mode or for the defib to trigger if not absolutely necessary.)

Today -- emboldened by my success -- I tried it on the tuba. The results so far are GREAT. I'm waiting on a 2" ball (ordered from Ferree's for even less cost, since I had to order valve guides from them anyway) to take on the lower bell section and bottom bow. But above the bottom bow I have at this point removed almost all of the dents, and the result looks fantastic.

Some observations:

1. This takes a LOT of effort. At least this is true on "vintage" instruments. I'm sure it would be easier on my red brass Cerveny tuba (which at some point may get the treatment for its 3 little dings), but that will require greater care. These old horns seem to have quite hard brass, and numerous passes (30, 40, 50, or more) are required to remove a significant dent.
2. The effort is mostly proportional to the depth of the dent, and not to its extent. So even tiny "point" dings can take a lot of effort. But they CAN be removed.
3. I have been very careful to proceed slowly and with great caution. I don't want to be careless and get hurt with this magnet, and I don't want to mess up the instrument through a moment of incaution. But so far things are going very well I can't imagine how much it would have cost me to have these dents removed by a brass repair technician.

One challenge yet to be met is to remove a fairly lengthy flattened area under a guard strip on the outer wrap. I'm hoping that I can do this without removing the guard strip, but we'll see. And I'm looking forward to getting the larger 2" ball which I will use on the bottom bow and lower bell section.

[ghmerrill]

I see that some people have looked at this thread, and so I'll post an update. with pictures (click on them to enlarge) ...

The first picture shows the horn shortly after I got it and you can see a lot of tarnish and dents up the outer tube and in the bottom bow on both the left and right corners above the bottom guard. The second and third pictures show the horn as of this morning after I have worked on it with a couple of magnetic dent balls. These also show the third valve kicker and shortening of the third and main tuning slides. There is still the dent on the front upper tube just up from the third valve that I continue to work on. This one was quite deep and had been caused by a fairly sharp edge with some force. But it is coming out. Just requires more effort over time. I've also polished the horn several times. There were a LOT of tiny "point" dents that the balls really got out, but these generally aren't visible in the older picture because that was taken with my iPhone.

There is still some work to be done (haven't worked on the bugle yet), but you can see the dramatic improvement. In the original pic you can see that the side of the outer run is flattened about half-way up, but that this has been significantly improved. I think I can do more there, even without taking the guard strip off. Total investment in the magnet and dent balls for doing this was a maximum of $75 (probably less, I?d have to look) including shipping. The magnet was about $40 or so, and each ball was in the $6-$9 range. I've just used two balls: a 1 7/16" and a 2".

You can also see the Amado water keys I added and the slightly modified Grime Gutter that I've taken to using since otherwise the valves tend to drip on me. This might be reduced whenever I decide to have the valves replated -- which I may do this summer, though they work quite well now. But once our concert season is over, I'll probably remeasure the cylinders and valves and send them off to Anderson. Should cost around $100 or maybe a bit more. At that point I'll have a pretty good Eb tuba in great condition for a total of around $450 -- even counting the tool cost (although the tools are useful on other projects). If I managed to buy one for that amount, I?d probably still have to put another $200 at least into it to get it to the shape this one will be in. And this one is quite neat, in part because it has the 17" bell and projects REALLY well in a large space. Plus, this has been a lot of fun to do.

[Eupher6]

I saw Lee Stofer work with one of those magnet/ball dent removers. Quick as a flash the dent was gone. I have no idea which type/strength the magnet was, but yeah, it was plenty strong.

I had the real sense that working with the magnet was a whole lot mo betta than working with dent balls, dent rods, etc.

[coolguy684]

I want to try this but I am afraid of damaging the horn...Perjaps I should leave it to a reapir shop for now.

[ghmerrill]

There are different strength magnets (and different sizes). I wish the one I had was a little larger (which would make it a bit easier to handle), but I don't think I'd want one much stronger. I think the one I have exerts about 200 lbs of force on the ball. I think it works "quick as a flash" if (a) it's a relatively shallow dent or the brass is relatively thin or soft, and (b) you've developed a bit of skill with it. Otherwise, rather than "quick as a flash" I've been going for "eventually works with no damage". The only horns I've used it on are the old Martin baritone and the Buescher tuba. My impression of both of those is that the brass is somewhat harder than on most contemporary instruments. At some point I will try it on the Cerveny red brass, but that's not really pressing and I want to be quite sure I've acquired the right touch since that horn is REALLY soft.

Bigger badder magnets cost you more bucks (at a rather alarming rate of increase of bucks per unit of increased strength).

It seems initially a quite intimidating thing to try, and I delayed for some time, even after I got the materials. However, I started on an instrument that I could have damaged without much penalty and moved to one that wouldn't be a huge financial loss if I screwed up. If you read some of the threads on TubeNet you will see a litany from several folks of utterly dire warnings about the dangers and ease with which you can mess up your instrument or harm yourself. But I found that, at least so far in my case, these warnings are about on the same level as others from various folks (most often repair techs) about such things as venting a piston valve (truly trivial if you're careful), lapping a slide, soldering on water keys, resoldering and aligning valve slides, etc., etc. This is not rocket science, and if you have some mechanical ability and can work with a degree of precision, take care, and follow reasonable directions, you actually can do a lot of this yourself. But it's not everyone's cup of tea. You definitely CAN get hurt with these magnets (or with a torch, or a drill, or a saw, or various chemicals). If you happen to have a lathe and a milling machine, you can do much more . We almost have my son's 1934 lathe working correctly, and once we get the motor back onto his 1974 mill (both acquired used at outrageously low prices), I may turn my attention to even more adventurous projects.

Dan Schultz has been a huge help to me in my (so far quite meager) efforts in brass repair and restoration. And so has Jacob Medlin (young custom horn maker in Greensboro: medlinhorns.com) who provided great information for installing Amado water keys. These guys have been great about sharing information about materials, supply sources, and techniques. My next move for the tuba is to replace the valve guides. I was really puzzled about how to do this and thought it might require brazing extra material on or even more complex operations to retrofit more modern guides (like Yamaha or Jupiter). Dan said (I paraphrase) "Well, those brass guides just screw into holes in the piston with 3-48 threads. Just unscrew them, get new guide blanks from Ferree's, shape them, and install them." Sure enough, I got a pair of pliers and easily unscrewed the first valve guide on the old Martin. Kraus actually lists Delrin valve guides -- but apparently they are "out of stock" for a while. Guess I'll go with the brass.

[red423]

this is a test,

[ghmerrill]

What does it take to pass it?

[red423]

testing again

trying this again, Ok I need some help, to buff a baritone marching band model, it is tarnished pretty good is there a wand or had held buffing wheels for this>> thanks red

[red423]

I got the dent balls and cheap magnet 212lbs removed most of the dents have two or three still holding on. I was going to make a couple rods with ball bearing ends to roll the last ones out. The horn plays really well, Got a little work to do but all in all I am lost on the buffing/polishing. My cheapo bench grinder with a cloth wheel and rouge is useless. Is there a small buffer or spray on cleaner I can use then hand buff with brasso or tarx??? thanks Oh thank you Dave for helping me to post you got back to me in a jiffy thanks, red

[Davidus1]

There are different strength magnets (and different sizes). I wish the one I had was a little larger (which would make it a bit easier to handle), but I don't think I'd want one much stronger. I think the one I have exerts about 200 lbs of force on the ball. I think it works "quick as a flash" if (a) it's a relatively shallow dent or the brass is relatively thin or soft, and (b) you've developed a bit of skill with it. Otherwise, rather than "quick as a flash" I've been going for "eventually works with no damage". The only horns I've used it on are the old Martin baritone and the Buescher tuba. My impression of both of those is that the brass is somewhat harder than on most contemporary instruments. At some point I will try it on the Cerveny red brass, but that's not really pressing and I want to be quite sure I've acquired the right touch since that horn is REALLY soft.

Bigger badder magnets cost you more bucks (at a rather alarming rate of increase of bucks per unit of increased strength).

It seems initially a quite intimidating thing to try, and I delayed for some time, even after I got the materials. However, I started on an instrument that I could have damaged without much penalty and moved to one that wouldn't be a huge financial loss if I screwed up. If you read some of the threads on TubeNet you will see a litany from several folks of utterly dire warnings about the dangers and ease with which you can mess up your instrument or harm yourself. But I found that, at least so far in my case, these warnings are about on the same level as others from various folks (most often repair techs) about such things as venting a piston valve (truly trivial if you're careful), lapping a slide, soldering on water keys, resoldering and aligning valve slides, etc., etc. This is not rocket science, and if you have some mechanical ability and can work with a degree of precision, take care, and follow reasonable directions, you actually can do a lot of this yourself. But it's not everyone's cup of tea. You definitely CAN get hurt with these magnets (or with a torch, or a drill, or a saw, or various chemicals). If you happen to have a lathe and a milling machine, you can do much more . We almost have my son's 1934 lathe working correctly, and once we get the motor back onto his 1974 mill (both acquired used at outrageously low prices), I may turn my attention to even more adventurous projects.

Dan Schultz has been a huge help to me in my (so far quite meager) efforts in brass repair and restoration. And so has Jacob Medlin (young custom horn maker in Greensboro: medlinhorns.com) who provided great information for installing Amado water keys. These guys have been great about sharing information about materials, supply sources, and techniques. My next move for the tuba is to replace the valve guides. I was really puzzled about how to do this and thought it might require brazing extra material on or even more complex operations to retrofit more modern guides (like Yamaha or Jupiter). Dan said (I paraphrase) "Well, those brass guides just screw into holes in the piston with 3-48 threads. Just unscrew them, get new guide blanks from Ferree's, shape them, and install them." Sure enough, I got a pair of pliers and easily unscrewed the first valve guide on the old Martin. Kraus actually lists Delrin valve guides -- but apparently they are "out of stock" for a while. Guess I'll go with the brass.

Thanks for posting this Gary. Very interesting. Good job on your horns!

[ghmerrill]

Why do you want to buff/polish it? There is a significant chance that by doing this you will thin the brass and affect the performance of the horn. If it plays "really well", then why not just play it?

[red423]

i can log in and cant post...............

[red423]

it rejects my postings if i write over a paragraph

[red423]

I logged out and back in so I'll try this. I am not looking to "polish" this baritone to mirror finish. Just clean it up a little. Due to its age the lacquer is fatigued, and the tarnish is really bad. I go this one really cheap. It had a stuck key, broken separator pins, and a lot of massive dents. I have since been able to remove many of the dents with dent balls, my magnet is advertised at 233lbs of pull but I don't think so. I have ordered a 550lbs of pull to see if I can really pull some bad dents out of the loaner the school loaned my daughter. We all know it is hard to get a kid to want to play let alone practice a min time everyday, and if we are able to provide a horn they are proud to play it makes the whole practice deal much more enjoyable. I also have several older horns I would like to just touch up. This finish issue has me lost I am trying navel jelly now along with citric jelly to see if it removes at least the tarnish from the tuning slides. I'll see. I would really love to get the baritone a uniform finish, not shiny mirror brass, just uniform. It's a marching band and looks are everything. yours red

[red423]

ok here's the problem posting If I hit quick reply it will tell me I don't have permission to post in a new window, if I hit ok, them down below hit advanced it will open a new window for me to log in then it will return me to the post quick reply page. This is after logging in to start with, is this normal??? red