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zdalton13

Top plate glue gap

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I've searched for and answer to this but I haven't come up with much, so any help would be greatly appreciated. I'm getting to work on my first violin and after gluing the two halves of the top plate and letting it dry overnight I noticed a gap of glue between the two boards and running the length of the seam. The gap is about the width of a hair. So my question is, should I split the two halves and try to re-glue it?

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18 hours ago, zdalton13 said:

So my question is, should I split the two halves and try to re-glue it?

By asking this it's clear you are concerned, and I think it is best to redo the joint. It's far easier to have a second try now, than for the joint to fail when the instrument is partially made, or finished, which would become a complicated repair. Saw it in two down the joint, and start over. The spruce top is easier to joint than the back, so the practice will come in handy anyway.

Although this thread started about planes for centre joints, you may find some useful information in it.

More here:

And more still:

 

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10 hours ago, zdalton13 said:

Thanks for the advice. I really appreciate it. Do you have any suggestions on how to separate the boards cleanly? the gap is too fine for a saw or a knife blade even.

Doesn't matter how wide the saw cut is. You'll be using the saw to cut away the previous joint, then re-planing and re-joining it. (presuming the wood is wide enough to do so)

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16 hours ago, zdalton13 said:

Thanks for the advice. I really appreciate it. Do you have any suggestions on how to separate the boards cleanly? the gap is too fine for a saw or a knife blade even.

Like was said just cut through the joint with a table saw or what ever. I always make my boards extra wide so I can do this a time or two if necessary. Also, if your glue is too thick the boards sometimes do not mate perfectly giving the problem you describe.

 

PS Nobody on this forum likes this, but if you're having trouble making a perfectly matching joint using a plane, you can set up a perfectly straight sanding board (I use an old 24" level on its side) and glue sandpaper to each edge. Put 120 grit on one side, and 240 grit on the other. I clamp it to the top of my table saw. Don't use too much pressure.  I get perfect joints from this no matter what they say. Planing is great and rewarding if you get good results, but in the end the point is a good glue joint, however achieved.

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1 hour ago, bkwood said:

  I get perfect joints from this no matter what they say.

I'm not trying to antagonize you, but you don't get perfect joints using your sandpaper method.  I don't even think it's "good enough". 

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One of the biggest challenges of jointing is getting both edges to mate perfectly. If you do them one at a time, edge up in a vice, there is a tendency to twist to the right on the start of the stroke and twist to the left on the end of the stroke (if you are right handed that is).

If you are having trouble with the centre joint, one trick is to plane both edges together. That way any irregularity or twist will be canceled out when you place the two edges together for gluing. Joiners have used this workflow for for centuries! 

other thing to note is to ensure you plane is sharp and the blade is straight (i.e. no camber).

Once you get it perfect, glue it right away! With a bit of practice it is possible to get a perfect joint. I routinely have to use a 5 x loupe on spruce tops to see where my centre join is.

 

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1 hour ago, Thomas Coleman said:

I'm not trying to antagonize you, but you don't get perfect joints using your sandpaper method.  I don't even think it's "good enough". 

Yes, I know many think that. Certain techniques are kind of a religion among woodworkers and I understand that and for the most part admire it.  My joints are very good, even invisible, and let's just agree to disagree if you want to believe otherwise.

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6 hours ago, Urban Luthier said:

One of the biggest challenges of jointing is getting both edges to mate perfectly. If you do them one at a time, edge up in a vice, there is a tendency to twist to the right on the start of the stroke and twist to the left on the end of the stroke (if you are right handed that is).

If you are having trouble with the centre joint, one trick is to plane both edges together. That way any irregularity or twist will be canceled out when you place the two edges together for gluing. Joiners have used this workflow for for centuries! 

other thing to note is to ensure you plane is sharp and the blade is straight (i.e. no camber).

Once you get it perfect, glue it right away! With a bit of practice it is possible to get a perfect joint. I routinely have to use a 5 x loupe on spruce tops to see where my centre join is.

 

Far better to clamp the plane on it's side and use a shooting board. You push the plate blank past the blade; this way you don't get any wobble which can happen when  free-hand planing.

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Thanks for all the help.

 Here is what I finally did: I found a dovetail saw was able to grab ahold of the glue joint and easily follow it all the way down. After tearing my hair out for  2 hours trying to plane one board at a time, the joint kept getting worse so I finally took Urban Luthier's advice and planed both boards together and finally got a good glue joint. I made the glue slightly thinner this time and I am happy so say the join it almost completely invisible.

However, I am going to have to be extremely careful from here on out as the thickness of the board at the glue joint is only 18.5mm after all my crazy planing. I know it's a learning process and I've got hundreds of miles to go.

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