|
Post by davey on Oct 28, 2020 11:10:45 GMT
Hi Folks, This is the tailpiece of a National Mandolin which is cracked halfway. It's said to be solid but I'd be inclined to reinforce it somehow. Any suggestions ?
|
|
|
Post by Andymccann on Oct 28, 2020 12:14:11 GMT
That doesn’t look solid (!) looks cracked most of the way through Soldering is one opinion but will look pretty bad cosmetically if not re plated Is it brass under the plating?
|
|
|
Post by davey on Oct 28, 2020 12:59:14 GMT
Yes, it's brass & I think it is cracked all the way through but apparently it's been like that for years. I've a feeling there's a cavity under the end of it so maybe a good amount of solder on the underside would do the job.
|
|
|
Post by Andymccann on Oct 28, 2020 13:14:29 GMT
if soldering then that gap will need to be closed up or it won’t run in the joint. Part of the trouble will be dis-colouring from the heat of the torch.
|
|
|
Post by bonzo on Oct 28, 2020 13:16:17 GMT
Some of the modern adhesives might be of some use. You can get gap filling ones if there is a cavity. How you would then match it to the existing metalwork is another question!
Best wishes to you all,John
|
|
|
Post by pete1951 on Oct 28, 2020 14:03:41 GMT
As there is a raised/embossed area , it may be possible to make a fairly thick brass bracket that could be shaped to fit under the old tailpiece. This could be soldered in. Pete I have a few modern spares [
|
|
|
Post by davey on Oct 28, 2020 14:22:50 GMT
Pete, could I buy one off you ? A couple of my Mandolins have the same tailpiece and I'd like to have a spare knocking about. Thanks
|
|
|
Post by pete1951 on Oct 28, 2020 15:57:02 GMT
Sure, will PM you later Pete
|
|
|
Post by Andymccann on Oct 28, 2020 18:46:43 GMT
I like sympathetic honest repairs, someone in 100 years could look at your tailpiece and appreciate the care you took over it
|
|
|
Post by snakehips on Oct 28, 2020 18:54:51 GMT
Hi there !
Laser welder repair will be the strongest AND the neatest repair with least amount of collateral damage to the nickel-plating.
I got 2 National tailpieces repaired at a dental lab with a laser welder. Been holding up under constant string tension for 4.5yrs
|
|
|
Post by Michael Messer on Oct 28, 2020 18:56:32 GMT
Davey,
Replacing a damaged tailpiece is not going to affect the integrity or value of the instrument in any way. However, if you really want it repaired, you should contact Richard AKA Snakehips on this forum. Richard is a dentist and has had tailpieces repaired with laser welding, whatever that is. I believe it is used in dental laboratories.
Shine On Michael
|
|
|
Post by Michael Messer on Oct 28, 2020 18:57:21 GMT
Ha... we were typing at the same time. Synchronicity.
Shine On Michael
|
|
|
Post by snakehips on Oct 28, 2020 19:29:45 GMT
Hi again !
Soldering, and if I’m not mistaken, welding, tig-welding, brazing all involve sticking two pieces of metal together, with another material (a mixture/alloy of metals and maybe other ingredients) so that the solder (or joining material) easily melts (at a lower temperature than the metals you are trying to join), to stick the main two parts together. The end result is a sandwich of the two original parts with the joining material in between. Solder can break at the join or break through the middle of the solder material, as it’s not as strong as the metals you wanted to join together.
Laser welding uses a laser to heat up the metal you want to join, in a very small spot, hot enough that the actual metal melts and flows and joins to the other part. The resultant laser weld is a one-piece continuous piece of metal, all fused together, all the same metal. It gives a much stronger bond than soldering, welding etc. If you can’t bring the two halves you want to join close enough together, you can laser weld in a thin piece into the gap, laser welding each side of the extra bit onto the ends of the main two parts - again forming a continuous piece of metal. The laser welder will not be a continuous laser beam, but little short blasts, melting/joining a small area at a time. Although the heat produced by the laser is enough to melt metal, the area heated is a small area - so not hot enough heat around the periphery, to damage the finish/platimg close by.
Laser welding shiny metal is a bit difficult as the laser beam can just reflect off the shiny surface, so they dust a black powder on the surface to be joined, to stop reflections of the light. Plus, black absorbs heat better.
Many industries use laser welders but the sort that are bought by larger dental labs are suitable for small jobs like this.
Without much Dentistry going on the last 6 months, Dental labs have been almost decimated of work. If you can find one still open, they might bite your hand off to do any work that will pay them something !
If you are anywhere near Glasgow, I used DTS-International dental lab
|
|
|
Post by snakehips on Oct 28, 2020 19:40:12 GMT
The Dental Lab guys did virtually no polishing or anything else after using the laser-welder, as they were worried they would polish off the nickel-plating. I didn’t actually watch them do the repair so I don’t know how long it took them but I went to lunch with the lab owners - and it was finished when we got back. Unlike tailpiece repairs by welding/brazing that I have seen, there is hardly any lumpy excess metal, like you see on those repairs. No grinding required afterwards Tailpieces have more or less a 90 degree bend - but in reality, it’s a bit more than that, at least under tension. Getting the repair angle right can prevent the repair being under a bending force/pressure when in use, under full string tension. I brought them another (unbroken) tailpiece (exact same vintage National tailpiece), and they used a large dollop of silicone putty impression material (think plasticine !) to make a jig, by mixing up the material, and pressing into the underside of the tailpiece onto the impression material. Once set, the non-broken tailpiece is pulled off the set putty, forming a shape to seat the broken tailpiece halves into the correct position/alignment, and holding them steady while laser-welding them together
|
|
|
Post by snakehips on Oct 28, 2020 19:45:32 GMT
Close-up, like in those pictures, you can obviously see bare brass metal, but compare the thin line of yellow brass to the width of the actual curve of the guitar top edge. The repair is far less obvious to anyone in the front row of an audience .
Audience ? What’s that again ?!!!
|
|