You are basically correct in there is usually nothing practically gained by anything in addition to glue but I wouldn't say its weaker.
Most of the techniques you are probably talking about are more for alignment than strength.
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You are basically correct in there is usually nothing practically gained by anything in addition to glue but I wouldn't say its weaker.
Most of the techniques you are probably talking about are more for alignment than strength.
Member
I can only relay what I have read or heard from woodworking professionals, but the statement by the OP does seem to be true. Anything beyond glueing does nothing to strengthen the bond between boards that are joined at the edges. Other ad-ons such as biscuits serve the purpose of (maybe) helping to align the boards. There are a couple of caveats, though. The boards need to be thick enough to provide a bonding surface (1/2" min.?), and the edges need to be in full contact with each other when clamped together. I have found that book-folding the boards in a vise and then hand planing a very slight hollow towards the midpoint of the joint results in a perfect joint from end-to-end. The only problem I sometimes encounter is when mating boards are not perfectly flat and some face-jointing may be required on the show side after the claps come off.
Contributor
I've joined many boards thinner than 1/2. I also remain unconvinced with respect to jointing an edge hollow, I don't consider it appropriate in every situation. Large panels seem to glue better with flat joints that are not hollowed, so long as you ensure that they're properly mated to one another.
For small and thin work the 'slightly' hollowed edge seems to come in handy.
Last edited by Brian Holcombe; 11-08-2016 at 10:52 AM.
Bumbling forward into the unknown.
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Curt, you might find this of interest: http://www.popularwoodworking.com/te...the_anvil_test
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I've often broken pieces of long-grain-to-long-grain glued wood just to see if the glue was stronger than the wood (offcuts). Always breaks in the wood and not the joint.
Mike
Go into the world and do well. But more importantly, go into the world and do good.
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[OP]
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Operating on the assumption that you have two edges, well planed, then cutting holes in them (with woodworker's precision) is not going to help. At least I do not see how. Even with dominos, you have still cut holes in good wood. I can understand wanting mechanical strength in case of glue failure, but we are not talking glue failure - that's a separate discussiion, IMO. As sloppy as most t&G joints are, I believe that they weaken the edge when glued. I've seen quite a number of boards with a broken tongue. If a simple square edge is as strong as you can get it seems reasonable that fussing with it is going worsen things. Fix it until it breaks.Originally Posted by Prashun Patel
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A loose T&G will indeed degrade the joint because the horizontal bonds will be weak, but I doubt many people in this discussion cut them that way.
A tight and properly glued T&G might not add anything to the strength, but it won't subtract. After all, if the glue is truly as strong as the wood then it doesn't really matter what path the glue joint follows so long as it's continuous. If the glue isn't as strong as the wood then the extra gluing area can only help. Either way you won't be behind in the deal except inasmuch as you've spent time doing stuff that wasn't needed.
The loss of cross-sectional area along the glue line due to biscuits/dominos/etc is negligible BTW. IMO they're a great productivity aid when gluing up, and they don't hurt the joint in any noteworthy way.
Contributor
I like T&G or dowels because they help align the joint.
It isn't terribly hard to align a joint without them, but there always seems to be a touch of slippage.
jtk
"A pessimist sees the difficulty in every opportunity; an optimist sees the opportunity in every difficulty."
- Sir Winston Churchill (1874-1965)
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Unless the biscuits or the domino's start to telegraph through to the surface.
Contributor
You need to make some cauls and use those for panel glue-ups. They really take the fussiness out of the process and you can eliminate those nasty dowels.
T&G is huge overkill for a glued edge joint. In my mind they are only for non-glued edge to edge assembly so that the individual boards can float with seasonal changes.
Moderator
Using cauls is great. But to align panels flat, it they can be a little tricky. Getting the clamps on the opposing sides can be tricky. The cauls need to be sized for the width of the panel. The glue up needs to be elevated so the clamps and cauls can engage. And, you need a set of clamps for each vertical set of cauls you use.
Dowels and biscuits and dominos take that pain out - especially on the widest and longest of glue ups like a dining table.
It is puzzling to me why anyone would have a strict religion about this. I use cauls sometimes, and dominos sometimes, and nothing sometimes. It's all dependent on convenience of getting a flat, flush joint. It appears from every single panel I've made that holes along the edge do not make any practical difference on the quality of the joint. The only thing that matters is the quality of the jointing.
Last edited by Prashun Patel; 11-09-2016 at 9:38 AM.
Contributor
The only issue with biscuits, dowels or Dominos is if you have to trim the panel and wind up cutting through the item. I have seen woodworkers in school do that. Maybe it's part of the learning process.
The problem with cauls is setting up to use them. As Prashun said, you need to elevate your glue up to be able to get the cauls and clamps under the work. Once you get your main clamps on, you can remove the cauls. You don't have to leave them until the glue fully sets - they're just needed to hold everything in place while you get the panel in clamps.
Mike
Go into the world and do well. But more importantly, go into the world and do good.
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Wow, you'd have to commit an epic measurement/math blunder to get into that sort of trouble. I think that the appropriate corrective action would be to learn elementary-school-level math (addition, subtraction, that sort of thing) rather than avoid biscuits.
Moderator
I have done it too. Not proud of it, but I sympathize with it.
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