I have read (and followed) instructions that when fitting biscuit joints, that PVA glue should be used, as this as well as gluing, due to water content , forces biscuits to swell.
I now tend to use Gorrilla Polyurethane glue on external work rather than PVA, anybody know if Polyurethane glue is suitable for use with biscuit jointing ?
Polyurethane glue isn't necessary for that joint. Poly is good for situations in which you need a waterproof connection, gap filling, or connecting odd materials together.
And Poly isn't not nearly as strong as PVA, either.
Gorilla glue cures on exposure to moisture. It helps to wipe the area with moist rag before gluing. Not sure what that means for biscuits. Perhaps wet the biscuits as you insert them, to activate both the compressed wood and the glue.
The expansion ration of Gorilla would place the biscuit pocket in danger of splitting throught the face of the board. And, like Mike said, why bother when PVA is stronger?
Regarding Gorilla, if you have ever seen it compared in a lab test as many of the wood mags have published you will see it is about the weakest stuff you can buy for wood. If you need extreme weather exposure use expoy. Can't recall the name of that 3M stuff, system 3?
Regard> I =A0have read (and followed) instructions that when fitting biscuit
many of the wood mags have published you will see it is about the weakest stuff you can buy for wood. If you need extreme weather exposure use expoy. Can't recall the name of that 3M stuff, system 3?
Gorila Glue is IMHO, the most over priced under peckered adhesive on the planet.
If TiteBondII doesn't cut it, time for epoxy(Raka, Systems3, West Systems, etc)
thought it was a myth but then I saw it in real life.
If you use biscuits with epoxy, they become a keying device.
Lew
Lately. I have become a huge fan (again) of Weldbond. I wouldn't glue a finely crafted mortise and tenon joint with it, but I find it does what it does better than anything: glue strips of plywood to the bottom of a solid surface countertop.
I wouldn't glue a finely crafted mortise and tenon joint with it, but I find it does what it does better than anything: glue strips of plywood to the bottom of a solid surface countertop.
SFWIW:
Ran some test years ago using some Corian samples, 12mmn CDX, and epoxy.
The epoxy joint didn't fail.
Lew
The Weldbond doesn't fail either.
Yes, you can use polyurethane glue with biscuits. I use water-based carpenter's glue with biscuits. The biscuits swell and lock the joint. If the biscuit is too close to the edge, it can swell a bump on the face. There are slight differences between biscuit brands.
Interesting. (not picking a fight) I always thought glue locked the joint. And biscuits more or less just help you line up the centers of the boards.
Mike... you like to live dangerously, eh? LOL
If used PROPERLY, a biscuit will add strength to a butt joint.
Again, not arguing here, I want opinions.....
How much strength is needed beyond what the glue provides for the average linear butt joint? Cabinet door panels for example, or a table top.
I understand that each plank of wood wants to warp in the opposite direction of the adjacent piece. Is that enough to break a glue-only joint?
Keep in mind, my middle name is overkill, so I'm usually the one using extra measures that aren't necessarily needed. :-)
A "butt joint" is end grain jointed to long grain. It's not typically used in door panel or table top construction.
What do you call the joint used to connect the edges of two or more boards to make a table top?
I call it an "edge" joint.
Ok, replace with "edge" joint. Anything to add?
In a properly prepared edge joint glued with PVA the wood will usually break before the glue joint fails.
A butt joint joined with just glue is extremely weak and should be reinforced.
According to a textbook I have, edge joining is described as a type of butt joint.
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