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29th June 2013, 01:18 AM #1Intermediate Member
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Biscuit Joints Glue or not to Glue
Hi
I'm going to use Haron biscuit joints on Tassie Oak to make panels, and I'm a bit confused as to whether or not to glue the actual biscuits.
From what I can understand the glue swells the biscuits to tighten the joints, but then this swelling may cause lumps in the panels. Are there any hard and fast rules about gluing these types of joints.
Cheers
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29th June 2013, 09:02 AM #2Skwair2rownd
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The biscuits are slightly smaller than the slot and are designed to swell.
No glue and you defeat the purpose of the biscuit.
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29th June 2013, 07:27 PM #3Taking a break
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Personally, I've never seen lumps form from biscuits.
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29th June 2013, 08:21 PM #4GOLD MEMBER
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Many, including professionals, will tell you that the biscuit adds no strength to the joint and that the sole purpose is for alignment only. If you subscribe to this school then the gluing of the biscuit makes no difference. I glue the biscuit myself, but don't get too fussed about. As for the biscuit swelling and causing a bump on the surface, this may occur if the biscuit is close to the surface as in thin timber.
Bob
"If a man is after money, he's money mad; if he keeps it, he's a capitalist; if he spends it, he's a playboy; if he doesn't get it, he's a never-do-well; if he doesn't try to get it, he lacks ambition. If he gets it without working for it; he's a parasite; and if he accumulates it after a life time of hard work, people call him a fool who never got anything out of life."
- Vic Oliver
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2nd July 2013, 10:22 PM #5Intermediate Member
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Thanks for that
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27th August 2013, 05:58 AM #6
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27th August 2013, 06:13 AM #7
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27th August 2013, 06:25 AM #8
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27th August 2013, 10:13 AM #9
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27th August 2013, 10:27 AM #10
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27th August 2013, 10:32 AM #11
If the Biscuits are well below the surface then I don't see why not.
Do they add no strength to the joint? Well, people use Biscuits for mitre joints. We know mitre joints are end grain to end grain so they are pretty weak without the biscuits.Visit my website at www.myFineWoodWork.com
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27th August 2013, 11:43 AM #12
And your point is? - As far as I can tell from that article even three biscuits aren't as good as a single tenon and, in any event, from my own experience I have easily disassembled a "biscuited" joint with a Stanley knife. They cut surprisingly easily.
There's not always room for three biscuits and more often that not I'll bet most only use a single biscuit.
Still, we have to go with what we believe suits us best and, for mine, it's a tenon.
Anyway this thread has the potential to go on and on and on and on and...so I'm done
Ian
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8th September 2013, 12:52 PM #13
The OP is a bit old but , Yes there are some, " hard and fast rules about gluing these types of joints." in my book.
First , I have seen biscuit's do some pretty incredible holding of timber under stressful loads, this was were a Elm 30mm thick table top was glued up in which the moisture content was high [ I thought it was dry enough ] it had Bread board ends held on with biscuit's , the table was kept in a sunny position in the house and when the top shrunk the biscuits held and the elm boards 100 x 30 just bent rather than let go at the join.
When I glue them I make sure I don't just put glue in the hole and push in a biscuit , I get a stick and spread it around the hole and then spread it all over the biscuit as well. What happens if you don't do that is , you can get a pocket of air trapped in the hole, every time just about, and you will push a dry biscuit through a small amount of glue sitting on top through to a dry hole.
I wouldn't use biscuits in a panel under say 16 mm thick if it were a polished feature, what I have seen happen where they are to close to a surface , say within 4 mm or 5 mm or under that, is a few months down the track the moisture that was in the glue dissipates and the biscuit shrinks back . I only use them in gluing up tops as an alignment aid and have seen shallow set biscuits shrink back and show up all the way down the top joints very clearly under a polished surface .
Cheers Rob
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3rd October 2013, 09:35 PM #14... and this too shall pass away ...
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Good grief ... you provided test data.
Ric, I'm sure you understand that we are all prejudiced in one way or another, and if the facts do not concur with our long held and cherished beliefs, they are likely to be dispensed with.
For myself ... I did my own tests comparing mortice and tenon joints with biscuit joints. The result is that I use both, but for every mortice and tenon joint I make, perhaps fifty to a hundred biscuit joints are made. When strength really matters, like doors that hold a heavy lead light panel, I use mortice and tenon joints, as well as in some areas that are difficult to reach with a biscuit cutter. Otherwise, I use biscuits, and am grateful to the inventor of this joint every time I pick up the biscuit cutter.
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3rd October 2013, 10:20 PM #15
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