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Super stubborn neck block


Michael Richwine
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I'm kind of embarrassed to raise this topic, because I thought I knew many of the tricks after so many years, but I am having the devil's own time getting the top off an old Mittenwald violin. I got most of the top loose without too much fuss, but the neck block has been resisting every attempt so far, and I have a customer who has been searching "everywhere" for just such a fiddle. I Made  new opening knife out of a good quality ham slicer with a uniform taper and single bevel so it doesn't tend to dig into the top at all or chew up the neck  block and I can use both hands on the blade for more leverage. No help. The old knife I've used since the 80s isn't making any headway. Working patiently back and forth with either knife doesn't seem to be making any progress, Heating the knives to 300-350F has worked with plastic glue in the past, but I don't seem to be gaining. 

Alcohol doesn't seem to help, although it has in the past.

Would an E string and an electric train transformer make a useful hot wire? 

I don't see any signs that tell me what kind of glue is in there. The glue line is thin with no visible squeeze-out to test.

I only have 7mm more to go......

Maybe I'll take razor knife with a .27mm thick blade pull the blade out of the spine, stone the teeth flush on the sides, and just saw through whatever glue line there is, using the top and ribs as guides.

What have you done in the past when nothing else was working? 

 

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I am an amateur so take this with a grain of salt.  

You already have the top released except for the upper block, right?  

Take an old hacksaw blade and grind one end of it into a chisel.  Feed it into the instrument from the lower bout and line it up with the stubborn glue joint.  Tap a few times with a small hammer.  That should do the trick.  Just be careful!  

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Michael

I just started  thread on this topic a just few weeks ago. I had the same problem compounded by the fact that I was only loosening the top bout for a projection correction so no access from the bottom and no possibility of removing and replacing any splinters. I ended up using two knives working  one under the other and tapping the handles with a small hammer. If it's not hide glue however I have no idea.

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Everything else is loose; it's just the neck block that's a problem. The place where I first worked made their own fish glue from sturgeon swim bladders, and this stuff was Strong and tough, especially when not aged, so I thought I had learned quite a bit about undoing glue joints.

I'll try impact in various degrees. Hadn't thought of it yet, so thanks for that idea, and the techniques. 

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I modified a 24" fine saw blade as a tool which can be used to start a cut into the upper block.  The blade is 0.80 mm thick but I ground the toothed side to 0.35 mm and it works quite well to give you a perch into the upper block so that you can continue with a long seam separator.   You can use it carefully as a saw since it has zero kerf to initiate a thin cut into the upper block. 

IMG_1754.JPG

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23 hours ago, Andreas Preuss said:

I had long ago the same problem with someone like Rene Morel standing in my back. 
 

In this ‘desperate’ situation I took a cello endpin made a slot at the end whichF699CCE4-F335-4C1F-BED9-BC89F664E577.thumb.jpeg.30db55cba329c696a0e28f6d4a155a51.jpeg could rest on the back of the opening blade. I inserted it through the endpin hole put it in position and started to hammer. See the diagram. 

I used this technique just the other day on a top block that had the same problem. 

Idiots thinking that gorilla glue and a cut nail are the only things that will hold the top to the block. 

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I use an 8" long artist's spatula (the blade, handle is another 4 1/2" or so); it's very thin, but still rigid enough that I can tap on the end of the handle with a small mallet to separate joins such as you are encountering. Judicious use of steam is a great help though, for very stubborn glue.

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I have a hotplate and could probably come up with a cannula and some tubing that would work.  It would be handy for other things, too, and worth the effort. Less potential for damage than impact, and I've got a  couple of other bodies with slivers that need soaking and re-gluing after following a tite-bond job. Most, but by no means all,  synthetic glues yield to heat. I was just about to go out to the shop and try a rod and hammer on the back of my opening knife, but I believe I'll make a steam generator first!

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International Violins larger size opening knife is a quite a bit too big for regular opening but works great for top blocks only, the blade is about 8" long, by 1" and thicker than a regular opening knife so it won't flex when you are trying to push it through the top block, I get it into position and tap it with my block plane in lew of an actual hammer, it should do the trick on most jobs, not sure about in your case though but it would be worth a try.

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2 hours ago, Michael Richwine said:

Off to the thrift shop to buy a pressure cooker. Ordered a neck steamer from Stew-Mac.  The needle's long enough to put steam where I need it. I'll need to be a bit judicious, but I'll report results. Thanks again to all who contributed!

I just used piece of 5/16 plastic hose with a sports ball inflating needle clamped on the end of the hose. I had an old kettle with a removable whistle that went on the end of the pouring spout. I drilled out the whistle for a 1/4" NPT to 5/16" hose barb  brass fitting. It works just fine for steaming joints, and didn't cost me anything, as I had all the parts on hand.

If you use a pressure cooker, make sure you keep the pressure relief valve intact for safety.

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Found a like-new pressure cooker for $15 at the thrift shop. It lets me adjust the steam pressure from 20 to 80 kpa. Also found brass tubing in 1.6 and 2.4mm OD, so don't need the Stew-Mac stuff. Only expensive thing was some 1/4" fuel line.  Got plenty of cork and stuff and can get chemistry stoppers as needed but should have something to test in the morning. May have to make a more durable connection for the hose to the steam pot, and I'll need to maybe craft an insulated handle after the concept proves out. so far, everything is testing out just fine. Total budget under $50 US. Most expensive item, 8 feet of 1/4 inch fuel line at $3.79 per foot. Have to have the hose pretty hot so that steam doesn't condense in the hose, and you need a needle in the hose to build up enough back pressure to get live, wet steam to the point you're interested in. I think 1000 watts should be plenty. Just need to be double careful to keep everything tight if there's any kind of pressure. I've been scalded before, and don't care to repeat.

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On 10/9/2021 at 3:26 PM, catnip said:

…You can use it carefully as a saw since it has zero kerf to initiate a thin cut into the upper block…

 

1 hour ago, Bill Merkel said:

I like Catnip's idea of a thin, kerf-less saw...

I think you are both talking about a saw with no set.  Since the kerf is the cut,  the blade of a zero-kerf saw would have no thickness and it would not cut anything.

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2 hours ago, Brad Dorsey said:

 

I think you are both talking about a saw with no set.  Since the kerf is the cut,  the blade of a zero-kerf saw would have no thickness and it would not cut anything.

Yes it does cut.  After grinding the toothed edge you are left with a fine flush cut saw... very similar to a flush cut dowel saw.   It is a very controlled cut and if you shine an led strip light you can monitor the progress.

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The steam worked great! I  made it with a steam tube that extends 11" -28cm from my hand piece, so I could put steam exactly where I wanted it. I propped the top open about 1 cm, shined a light in with my left hand, and played steam along the joint for a minute or two, then tried a knife. The steam condenses as it gives up its heat, but the whole process took about  four minutes, with no distortion to the top, and I was able to pick up the excess moisture quickly. While the steam generator was hot, I used it to pick some slivers  off another open violin that had been repaired with Titebond. I can't tell yet what kind of glue was giving me so much trouble earlier. The glue line was very thin, and it was still a little tacky after it came apart. I'll take a closer look tomorrow. Doesn't look like I did any damage on my earlier attempts, which is gratifying. Even though it's just a $2500 Neuner violin, I try to treat them all with respect.  I may shorten the hose a bit, but all in all, the rig works fine. There's always room for improvement, but I have customers who want stuff done, too.

 

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