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Pegbox Repair Question


Thomas Knight
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  Hello MN luthiers and top instructors like Jacob Saunders, Blank Face, and any others. I would like input on an idea I have for repairing a pegbox crack on a nice violin recently posted on this forum that extends through two peg holes and have expanded over time. Even with a strong clamp the crack(s) cannot be closed. I will of course first flush out the crack thoroughly with water and low air pressure using the string method Jacob was so kind to share with us a while ago, but I am looking at a repair if the gap cant be closed.

  I recently purchased a 1923 Deckel GK2 pantograph/profiler made in Germany. It is is immaculate condition and accurate to under .001" (.025 mm). I can cut a perfect very thin slot where the crack exists of about .020" (.5mm) and profile a matching insert of the exact thickness, width, and depth and insert and glue it, then bush the two peg holes. Feel free to give an opinion--I want to see if the classically trained experts think this is a good idea.

VIO SEITZ PEGBOX CRACK.jpg

VIO SEITZ PEGBOX CRACK B.jpg

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4 hours ago, jacobsaunders said:

That one would seem to have old spiral bushings in, that I suggested last time. If you take them out, and get the remaining dirt out of the crack, it should go together

I am simply amazed you could see the bushings by the photos. I had to look at the pegholes with a 10x jewelers microscope to see that they did indeed have thin bushings and you are right (as usual). Many thanks to Jacob for his efforts to teach us the proper way to do a repair.

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16 hours ago, jacobsaunders said:

That one would seem to have old spiral bushings in, that I suggested last time. If you take them out, and get the remaining dirt out of the crack, it should go together

It won't any longer now that he has Deckelized it.

 

17 hours ago, Thomas Knight said:

I recently purchased a 1923 Deckel GK2 pantograph/profiler made in Germany. It is is immaculate condition and accurate to under .001" (.025 mm). I can cut a perfect very thin slot where the crack exists of about .020" (.5mm) and profile a matching insert of the exact thickness, width, and depth and insert and glue it, then bush the two peg holes. Feel free to give an opinion--I want to see if the classically trained experts think this is a good idea.

These pantographs are wonderful machines and capable of great things, but I would never use mine for such a repair.  As Jacob mentioned, you could very likely have gotten it to go back together with some patience and further consultation here.  I don't think I have ever removed and replaced wood to repair a peg box crack in over 40 years of doing this work.
Though the Deckel is capable of very accurate work I'm pretty sure, if it was indeed necessary to remove wood, one could get a far better result by cleaning up the shape of the crack by hand and fitting a tapered, rather than straight sided piece of wood into the resulting (also tapered) slot.

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2 minutes ago, Mark Norfleet said:

It won't any longer now that he has Deckelized it.

 

These pantographs are wonderful machines and capable of great things, but I would never use mine for such a repair.  As Jacob mentioned, you could very likely have gotten it to go back together with some patience and further consultation here.  I don't think I have ever removed and replaced wood to repair a peg box crack in over 40 years of doing this work.
Though the Deckel is capable of very accurate work I'm pretty sure, if it was indeed necessary to remove wood, one could get a far better result by cleaning up the shape of the crack by hand and fitting a tapered, rather than straight sided piece of wood into the resulting (also tapered) slot.

The second photo is the first pic with a 'paint' program drawing a black line where the cracks are. I was waiting for expert opinions and input before I did anything to this violin as I am trying to follow the advice of those far more advanced than I. Your point about a tapered insert is well taken. It would be far better of a mechanical lock than a parallel insert.

  I am wondering about cheeks and grafts where a powder fit is used to find the highs and lows--the Deckel would be perfect I would think. When I designed and produced automotive performance parts we were dealing with specs of .00015", and the Deckel is capable of that type of accuracy due to it's 1:1.5 down to 1:10 capabilities. A fixture could hold a scroll and with a reduction ratio so high a 20mm x 80mm x 2mm thick cheek groove would use a 200mm x 800mm x 20mm pattern. Even at 1:5 it would be far more accurate than by hand. Just thinking.

 

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1 hour ago, Mark Norfleet said:

It won't any longer now that he has Deckelized it.

I  hadn't realised that "Dekeliz(s)e" was a word

17 minutes ago, Thomas Knight said:

 

  I am wondering about cheeks and grafts where a powder fit is used to find the highs and lows--the Deckel would be perfect I would think. When I designed and produced automotive performance parts we were dealing with specs of .00015", and the Deckel is capable of that type of accuracy due to it's 1:1.5 down to 1:10 capabilities. A fixture could hold a scroll and with a reduction ratio so high a 20mm x 80mm x 2mm thick cheek groove would use a 200mm x 800mm x 20mm pattern. Even at 1:5 it would be far more accurate than by hand. Just thinking.

 

I was once upon a time friends with a violin restorer from a museum. He bought himself and was ecstaticly enthralled with an extortionately expensive dentist drill. Goodness knows how much he wrecked with that before he went back to basics

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50 minutes ago, Thomas Knight said:

 

  I am wondering about cheeks and grafts where a powder fit is used to find the highs and lows--the Deckel would be perfect I would think. When I designed and produced automotive performance parts we were dealing with specs of .00015", and the Deckel is capable of that type of accuracy due to it's 1:1.5 down to 1:10 capabilities. A fixture could hold a scroll and with a reduction ratio so high a 20mm x 80mm x 2mm thick cheek groove would use a 200mm x 800mm x 20mm pattern. Even at 1:5 it would be far more accurate than by hand. Just thinking.

 

Using pantographs to rough out patches while working from a cast is not a new idea… working directly on the instrument is incredibly risky. 

 

 

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40 minutes ago, jacobsaunders said:

I  hadn't realised that "Dekeliz(s)e" was a word

I was once upon a time friends with a violin restorer from a museum. He bought himself and was ecstaticly enthralled with an extortionately expensive dentist drill. Goodness knows how much he wrecked with that before he went back to basics

Thank you Jacob. This is the input I am looking for. I think we can add 'Deckelize' to our Maestronet lexicon.

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12 minutes ago, Jerry Lynn said:

Using pantographs to rough out patches while working from a cast is not a new idea… working directly on the instrument is incredibly risky. 

 

 

  Thank you Jerry. I ask these questions for this very reason. It is the input I wanted and am grateful to receive.

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2 hours ago, jacobsaunders said:

I  hadn't realised that "Dekeliz(s)e" was a word

I was once upon a time friends with a violin restorer from a museum. He bought himself and was ecstaticly enthralled with an extortionately expensive dentist drill. Goodness knows how much he wrecked with that before he went back to basics

I chuckled when I read this. It reminds me of a Red Green story, where his neighbor Old' Bill,  bought an army surplus helicopter. Upon trying it out, his neighbor harvested 60 acres of trees before he figured out how to get it upright. :lol:

Power tools are a double edged sword: they can speed up a lot of work compared to working by hand, but they can also do a lot of damage in very short order.

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51 minutes ago, Bill Yacey said:

I chuckled when I read this. It reminds me of a Red Green story, where his neighbor Old' Bill,  bought an army surplus helicopter. Upon trying it out, his neighbor harvested 60 acres of trees before he figured out how to get it upright. :lol:

Power tools are a double edged sword: they can speed up a lot of work compared to working by hand, but they can also do a lot of damage in very short order.

One of my good friends is a pilot for a local helicopter med-flight operation and regularly flies over my house.  I've often thought it would be fun to ask him to just briefly land in my yard once all the leaves have fallen.

3 hours ago, Thomas Knight said:

  I am wondering about cheeks and grafts where a powder fit is used to find the highs and lows--the Deckel would be perfect I would think. When I designed and produced automotive performance parts we were dealing with specs of .00015", and the Deckel is capable of that type of accuracy due to it's 1:1.5 down to 1:10 capabilities. A fixture could hold a scroll and with a reduction ratio so high a 20mm x 80mm x 2mm thick cheek groove would use a 200mm x 800mm x 20mm pattern. Even at 1:5 it would be far more accurate than by hand. Just thinking.

 

The deckel might be great for roughing things out, but I think in practice you would find the fit is not as good as the theoretical precision of the machine.   Cutter/wood interaction is not as predictable as when cutting metal or other more homogeneous and rigid materials.  Variations in the amount wood removed due to attack angle of the cutter relative to grain direction alone will (I'm pretty sure) produce a less precise fit than an experienced and diligent restorer could achieve by hand scraping/fitting using chalk (powder) to fit the surfaces.
I'd be happy to be proven wrong though!

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2 hours ago, Wood Butcher said:

Seems the best case here, would be to let someone else repair the scroll properly.

There comes a time when all of us must take the plunge and do something ourselves.  It is not my first repair. I am asking for opinions and feedback on thoughts and methods. I have been unconventional all my life and in the field of automotive supercharging considered among the best in the world in research, development, design, and prototyping. So I am retired with hundreds of violins in my collection--some rubbish and some very good. I am blessed with machines most people will never own and am well versed in feed rates, direction of grain, etc. Soft alloys have similar issues as wood when machining them and also have built thousands of wood templates so I am aware of the potential problems. I simply want input. Having experts express their thoughts allows us to learn not just how, but why. The 'why' is far more valuable to me than how. Every response from someone is a learning opportunity. I have a library of documents and responses from the incredible instructors on this forum.

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As you and others have mentioned, clean out the cracks as well as possible and remove all traces of the existing bushing.  I'd then suggest figuring out how best to clamp it for gluing, what type of clamp you're going to use, how many etc. In this case, I'd make a cast of the back of the scroll and a counterpart for the top of the peg box walls so that you can apply enough pressure.  After gluing with a strong glue, I'd suggest keeping the clamps on while you clean up the holes again with a reamer.  The holes already look on the large side, but I'd consider enlarging them very slightly more before bushing.  There are several ways that you could proceed with the bushing, spiral or solid, but which ever you choose, I'd again suggest leaving the clamps on while fitting and gluing them.  Since the holes are large you could consider "capping" the bushings to match the wood wood of the scroll, but that is both more time consuming and difficult to do.  Most importantly, imo, would be when you reinstall pegs, that you shave them down to a slightly smaller diameter than you might normally and be especially attentive to the fit and how they are working.  Finally, depending on how far you've been able to get the cracks together, it may be preferable to use various fillers rather that trying to insert wood.  

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3 hours ago, Thomas Knight said:

...I am asking for opinions and feedback on thoughts and methods...

Here's mine:  If, after you remove any bushings and previous additions, the cracks don't want to close under a reasonable* amount of clamping force, I think that filling the cracks with bits of wood is a reasonable thing to do.  And Deckelizing the cracks is probably the only way you will be able to get good-fitting filler bits.

*I think that a crack that only closes under unreasonable clamping force is likely to re-open in the future.  Or, if it doesn't re-open, the clamping force will cause stresses that will encourage new cracks or other problems.

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1 hour ago, Philip Perret said:

As you and others have mentioned, clean out the cracks as well as possible and remove all traces of the existing bushing.  I'd then suggest figuring out how best to clamp it for gluing, what type of clamp you're going to use, how many etc. In this case, I'd make a cast of the back of the scroll and a counterpart for the top of the peg box walls so that you can apply enough pressure.  After gluing with a strong glue, I'd suggest keeping the clamps on while you clean up the holes again with a reamer.  The holes already look on the large side, but I'd consider enlarging them very slightly more before bushing.  There are several ways that you could proceed with the bushing, spiral or solid, but which ever you choose, I'd again suggest leaving the clamps on while fitting and gluing them.  Since the holes are large you could consider "capping" the bushings to match the wood wood of the scroll, but that is both more time consuming and difficult to do.  Most importantly, imo, would be when you reinstall pegs, that you shave them down to a slightly smaller diameter than you might normally and be especially attentive to the fit and how they are working.  Finally, depending on how far you've been able to get the cracks together, it may be preferable to use various fillers rather that trying to insert wood.  

  Great ideas. I took it to an expert here in Tampa and the scroll is crooked, the neck is also 1/4" too short, and the standoff way to low at 1.5mm so we are going to do what all the experts have agreed on which is to clean out the cracks and clamp it properly. The graft requires the G and A holes to be bushed anyway, so he is taking me on as a semi apprentice and we will do it right. 

  I have a large number of damaged backs and am thinking to carve bridges from them with the Deckel. Old Saxon 5-6mm thick in the centers. What are thoughts on that? Well seasoned wood, and I can make any shape and inscribe them as well.

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12 minutes ago, Brad Dorsey said:

Here's mine:  If, after you remove any bushings and previous additions, the cracks don't want to close under a reasonable* amount of clamping force, I think that filling the cracks with bits of wood is a reasonable thing to do.  And Deckelizing the cracks is probably the only way you will be able to get good-fitting filler bits.

*I think that a crack that only closes under unreasonable clamping force is likely to re-open in the future.  Or, if it doesn't re-open, the clamping force will cause stresses that will encourage new cracks or other problems.

That was about what the expert here said. Sometimes the wood just wont quite close. He prefers to use a sliver of wood instead of any filler. Thank you for your help.

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I am not a luthier, but I am curious as to why nobody has suggested an inside cheek after closing the crack followed by insertion of a carbon-fiber bushing if the peg hole isn't too big. This repair can be very close to invisible.

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1 hour ago, GeorgeH said:

I am not a luthier, but I am curious as to why nobody has suggested an inside cheek after closing the crack followed by insertion of a carbon-fiber bushing if the peg hole isn't too big. This repair can be very close to invisible.

  Hi George, I will be doing the work under the supervision and guidance of the expert. When the graft is done it will be an 'inside cheek' so to speak as it will extend to even with but above the D peghole so it will help reinforce the crack(s) which are between the bass side G and A and extending past the G.

  This is another question for the experts. Should the scroll be cut for the graft first before the crack closed? It will allow the crack that extends toward the ducktail to be open at one end making it easier to close. If the crack is closed at the same time as the new neck blank inserted that would allow a solid backing for the pegbox wall during clamping and help keep the wall from distorting. Any thoughts?

 

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9 minutes ago, Thomas Knight said:

This is another question for the experts. Should the scroll be cut for the graft first before the crack closed? It will allow the crack that extends toward the ducktail to be open at one end making it easier to close. If the crack is closed at the same time as the new neck blank inserted that would allow a solid backing for the pegbox wall during clamping and help keep the wall from distorting. Any thoughts?

 

I would remove the neck before doing the crack repair if I was certain I would be doing a graft.  I wouldn't however be thinning out the peg box wall until I explored cleaning and gluing the cracks.  Once you start thinning things like that out, it complicates glueing.  Thinning the peg box wall might well allow the the two sides of the crack to brought together more readily, though I would do what I could to avoid that.  What I would be VERY unlikely to do would be gluing the crack at the same time the graft was glued.  In theory it might seem like a good idea to the inexperienced, but it would be much better, in my opinion, to have the crack sorted out before fitting and gluing the graft.  Thinned out peg box walls move around enough even with sound peg boxes and keeping gluing operations as simple as possible is best, presuming one is using traditional hot hide glue... 

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I repaired a guitar head several years ago that had a similar crack. What I did was clean the crack, glue and clamp. After the glue dryied I used a several bowties made out of aluminum inserted deep enough that I could use veneer of close grain to hide the repair. The bowties are so strong it prevented the crack from opening again. 
 

In your situation I would remove the bushing and use one bowtie between the pegholes and one bowtie after the peghole just before the end of the crack toward the ducktail. You can use a dogbone instead of the bowtie method but either method will stop the crack from reopening and if you’re lucky with the selection of the veneer or wood it will almost be an invisible repair.

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1 minute ago, Mark Norfleet said:

I would remove the neck before doing the crack repair if I was certain I would be doing a graft.  I wouldn't however be thinning out the peg box wall until I explored cleaning and gluing the cracks.  Once you start thinning things like that out, it complicates glueing.  Thinning the peg box wall might well allow the the two sides of the crack to brought together more readily, though I would do what I could to avoid that.  What I would be VERY unlikely to do would be gluing the crack at the same time the graft was glued.  In theory it might seem like a good idea to the inexperienced, but it would be much better, in my opinion, to have the crack sorted out before fitting and gluing the graft.  Thinned out peg box walls move around enough even with sound peg boxes and keeping gluing operations as simple as possible is best, presuming one is using traditional hot hide glue... 

 Excellent suggestions. This is exactly what I ask for. Yes, hide glue will be used. Before I do anything I am removing the neck, setting up a wick effect wash (Jacob's system) and hopefully the cracks compress easily.

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