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30th July 2023, 05:25 PM #1Novice
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Glue Failing?? chopping board, too much clamp force?
I have started making some chopping boards and some (a lot) of the glue joints seem to be failing. It is almost always when using merbau. I am wondering if I am using too much clamp force?
The merbau is old and weathered so I don't thing tannin is the problem. I have used the jointer to make sure the surfaces are flat. What am I doing wrong?
Cheers
Jason
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30th July 2023, 05:55 PM #2GOLD MEMBER
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Possibly too much clamping force. What glue are you using?
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30th July 2023, 06:17 PM #3Novice
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Titebond III
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30th July 2023, 06:34 PM #4GOLD MEMBER
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Titebond 3 is good stuff. If the wood is very dry it might be drawing the water out of the glue before it can cure properly. Have you tried applying it liberally to both surfaces?
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30th July 2023, 06:57 PM #5Novice
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Plenty of glue used
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30th July 2023, 08:07 PM #6SENIOR MEMBER
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I'm not familiar to the quirks of most Australian/southern hemisphere woods but two things to try.
If your gluing straight from a jointed surface, try a couple passes on each surface with some 60 or 80 grit. PVA glues need a surface that allows them to grab on with the billions of interlocked polymer stands or it'll fail. Apply the glue as usual and then run along with your finger, smoothing it out over the entire width of the joint, in both directions. If the wood is resistant to the absorption of the polymer strands in the glue, then ya, too much pressure will squeeze out the glue without allowing it to do what it's designed to do - so less pressure. Say, snug it up just enough to stop the boards slipping around as they do. Maybe an eighth turn more, but that's it. Titebond III has excellent gap filling qualities so there's no real worry about that, but you may have a more visible glue line.
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30th July 2023, 09:39 PM #7SENIOR MEMBER
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When you say glue is failing what exactly is happening?
A few questions:
- Do you know moisture content of wood?
- are you following general guidelines of wood construction ie no end grain to edge grain etc
- are you clamping within the open time?
- are you within the glues working temp? It's pretty cold ATM, are you doing glueups late at night? When the temps dip?
- how old is your glue? Have you tried gluing other bits of wood/ scrap merbau together does it hold?
A photo of failed joint might also help
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31st July 2023, 09:27 AM #8Novice
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31st July 2023, 10:38 AM #9GOLD MEMBER
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I’m on the Mornington Peninsula and do not have any problem with glue ups.
I use old Merbau and Titebond 3.
I also put as much pressure on the joints using Bessey clamps as I can but I do not do any glue ups if the temperature is below ~16c and I also clamp for 48 hours.
I think temperature could be a factor in your problems. Can you bring the chopping boards inside overnight? Just a thought…
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31st July 2023, 10:45 AM #10Novice
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31st July 2023, 11:04 AM #11GOLD MEMBER
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31st July 2023, 11:07 AM #12SENIOR MEMBER
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Clamping for longer than 24 hours won't make much of a difference.
The final thing i'd suggest is gluing up a scrap piece of merbau but before you glue up wipe it down with turps or similar. Let the thinner dry and proceed with glueup.
If it holds then its the oils in the timber causing the joint to fail, in which case i'd probably just get rid of the merbau is use something else.
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31st July 2023, 11:34 AM #13
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31st July 2023, 12:04 PM #14GOLD MEMBER
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"According to Jeff Loflin, glue specialist at Franklin International (maker of Titebond wood glues), salt (and sugar, too, by the way) can react with wood glue and alter its composition, resulting in a weakened joint."
Should I use salt in my glue to prevent slipping? | Wood
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31st July 2023, 12:26 PM #15Senior Member
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