| > It's a shame this myth continues on the wreck. Many a great kitchen | cabinet | > has been built with biscuits and they haven't fallen off the wall. | If one | > takes time, you will learn biscuits are a wonderful tool to use in | > woodworking, and they easily perform structural tasks. |=20 | Nobody is saying biscuits are useless, but just because the cabinet | hasn't fallen off of the wall doesn't mean they strengthen the joint | (depending on the joint). |=20 | Certainly a biscuited right angle joint would be stronger than a butt | joint, but I'd like to hear the science of how a biscuited edge joint | would be stronger than a non-biscuited edge joint. |
This may not please you, but; a biscuit seems to me to be of about the = same value to a joint as a floating tenon in that it will serve to = increase the glue area thereby increasing the durability and stability = of the joint.
That said, the actual durability of the joint would seem to be dependant = upon the quality of the glue and glue-up, and the drying time. Issue =
157 of WOOD (Sept 2004) has a comparison of various glues - = polyurethanes, PVA's and water-resistant PVA's. The following tests = used only but joints with no additional reinforcment. All the glues = tested seemed to achieve maximum strength after 30 minutes of drying = time except for the polyurethanes which required 120 minutes.
When joining edge grain to edge grain, almost all the glues tried = resulted in the wood failing before the glued joint. The pressure = required to "break" the joint exceeded 1600 PSI in all cases. In this = instance, a tenon of any variety would seem superfluous. =20
When gluing edge grain to end grain, the results are quite different. = The use of a tenon/biscuit, dowels, cope and stick is highly = recommended. =20
The polyurethane glues failed between 350PSI and 800PSI, the = water-resistant PVA's failed between 1200PSI and 1800PSI, and the PVS'a = failed between 1150 PSI and 1400PSI. Of note is the fact that 4 glues = surpassed all others in this area (the wood failed before the glue). = These glues are:=20 Elmer's Carpenter's ProBond Interior/Exterior Titebond Moulding and Trim Loctite Professional Wood Worx Elmer's Probond Interior =20
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PDQ