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Separating broken button from neck heel


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#1 Jimbow

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Posted 13 February 2007 - 11:25 AM

Does anyone have suggestions for removing a broken button which is solidly glued on to the neck heel without damage to the original wood? A search brings up many posts describing sawing the neck heel and adding a wedge. This appears to be the accepted method.

I've been reluctant to try sawing because of the extra fitting and touch up required. Also messing up on sawing angle, could be..... well, messy!
In my limited experience, the buttons have come loose from the heel without much problem but accasionally have had to use a thin blade and water or alcohol and some 'persuasion'. This could cause some distortion damage to the button.
I reinforce a broken button with an invisible thin maple inlay extending under the block and into the button. I've used this technique on half dozen violins and a few cellos with no problems to date.

With that in mind, what would be the feasibility of drilling some tiny holes into the button from the broken end to allow water to soak into the glue joint and allow separation. Maybe extended interior soaking and/or a heat gun might help. The holes would later be removed as part of cutting out the inlay recess. Does this sound at all workable?

Any thoughts or other other suggestions? TIA

Jimbow

#2 fiddlecollector

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Posted 13 February 2007 - 01:21 PM

Is the neck free from the body??

#3 Brad Dorsey

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Posted 13 February 2007 - 01:31 PM

When I remove a neck, I usually saw through the neck heel close to the button. But when I'm in your situation, with the neck already out and the broken-off button still attached to it, I have always successfully separated the button from the heel by carefully prying it off. I use the same opening knives that I use for top removal, working them through the glue joint starting from the broken side of the button. I don't use water or heat.

Here's how I do the rest of the job: Remove the back from the ribs. Glue the button back on the back. Make a plaster cast of the back. Inlay a re-inforcing patch in the button. Reglue the back to the ribs. Reglue the neck. The patch is invisible from the ouside, and the button is now stronger that when it was new.

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#4 Jimbow

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Posted 13 February 2007 - 02:11 PM

quote:


Originally posted by: fiddlecollector
Is the neck free from the body??


Yes, the neck is out of the body. I have also removed top plate, the upper block, and loosened the ribs (for a few inches) for access.
Jimbow

#5 Jimbow

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Posted 13 February 2007 - 02:15 PM

"....Here's how I do the rest of the job: Remove the back from the ribs. Glue the button back on the back. Make a plaster cast of the back. Inlay a re-inforcing patch in the button. Reglue the back to the ribs. Reglue the neck. The patch is invisible from the ouside, and the button is now stronger that when it was new. "

Thanks Brad,
Sounds about what I do except for the plaster cast. What is that for?
(Possibly to support the button area while carving inlay recess?)

I was really glad to hear you say " the button is now stronger that when it was new." It always seemed that way to me too but I was afraid it was just my wishful thinking.
Jimbow

Edit note: I use SystemThree T88 Structural Epoxy and feel it is more appropriate for a permanent button repair patch on a German Student violin than Hide glue or Titebond II. Sound reasonable?

#6 Brad Dorsey

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Posted 13 February 2007 - 04:16 PM

The cast is to support the button while excavating the patch bed.

When the button is new, it is weak because the purfling cuts partway through it. I excavate the patch bed well into the purfling, making the cavity deep enough to only leave about a half a millimeter at the center. When the patch is finished, it replaces a significant part of the purfling, eliminating the weakness that the purfling gave to the button.

I have always glued patches with hide glue. I think that a well-fit patch glued with hide glue will be plenty strong. If the patch is not well-fit, the other glues you mention might be better because they are better gap fillers.

Normally for interior repairs I remove the top. Removing the back risks damaging the button or messing up the button/neck heel joint. But when the button has already broken off the back, button damage becomes a moot point and I remove the back. Usually I find it unnecessary to replace the upper block when doing this proceedure.

Time flies like an arrow.  Fruit flies like a banana.


#7 Jeffrey Holmes

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Posted 13 February 2007 - 06:31 PM

Don't use water. You'll distort the mating of the button to the back plate.

Do use a partial cast when performing this repair.

I wouldn't use epoxy. I would use hide glue.

#8 Jimbow

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Posted 13 February 2007 - 07:56 PM

Thank you Brad and Jeffrey,
You make some excellent points which will help me and others.
I agree it is important to fit the inlay patch accurately. I chalk mine in and use a long rectangular pattern as wide as possible yet stay inside the curves of the button. I will try to go deeper for strength as Brad suggests and not worry about cutting into the purfling which shouldn't be in that location anyway. I know the purfling is in the button area by tradition although it serves no functional purpose there, rather it weakens the button and neck integrity severely.

Violin makers are always discussing how to improve on the violinmaking craft. One obvious thing that could be done is to change the purfling pattern design so as to not weaken the violin (button) in this most vulnerable area. One of the few attempts to accomplish this was the American made Wilkanowski violin of the 1940's. The purfling formed a deep W below the button thus eliminating that normally weak area.



Jimbow

#9 Jeffrey Holmes

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Posted 13 February 2007 - 11:20 PM

Alcohol, used very locally and given time to work, may help you.

The button area issue has been addressed by a number of makers in the past in various ways. Read up a bit on J. B. Guadagnini's work.

#10 barnesviolins

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Posted 14 February 2007 - 12:24 PM

If you haven't cut it yet.....

I like Jeff's suggestion of alcohol and I use a razor blade coming from the inside out working it gently. I find the thinner blade works well for me. Along with lots of patience.

Dorian
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#11 Jimbow

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Posted 14 February 2007 - 01:39 PM

quote:


Originally posted by: barnesviolins
If you haven't cut it yet.....
I like Jeff's suggestion of alcohol and I use a razor blade coming from the inside out working it gently. I find the thinner blade works well for me. Along with lots of patience.
Dorian


Thanks Dorian,
Your response was timely and it worked perfectly in about two minutes!

Using a disposable plastic pipette to just dampen the blade with alcohol, I pressed the razor blade into the joint with slight pressure. Worked like magic!
I usually use my thin artist palette knife that is also used for top removal but the sharp, new single- edge razor blade worked much more effectively along with the alcohol.

I knew I could count on you guys to answer my question ..... and much more!
Thank you.
Jimbow

#12 barnesviolins

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Posted 14 February 2007 - 03:18 PM

Godd Job Jimbow!

Glad to hear of your success.

Dorian
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