Fencepost2
25th December 2008, 05:59 PM
The current Fine Woodworking has a comparison of the strength of 15 common framing joints. They were all tested to breaking point. The half lap and bridle joints came out strongest, with M&T and floating M&T very close behind.
That surprised me, but it makes sense as they explain that the glue faces of the half lap and bridle joints get clamped, whereas a M&T joint though squeezed up does not actually get any clamping on the glue faces.
But the detail that always worries me is how tight a M&T should be for optimal strength? If the side pressure of clamping a half lap or bridle is important, the side pressure created within a M&T by the tightness of fit must be highly relevant. I have varied between "tap in with a mallet" and "slide in neatly without it rattling" but I have never come across any actual test comparisons of goodness of fit.
Can anyone clue me in please?:?
(Note, dowels, dominos, and biscuits were okay for most applications but when they failed it was usually the stile that split down the grain at the point where the dowel or domino ended. The implication here is that for strength make your dowels, dominos, biscuits, and floating tenons as long as you can.
It is a good article and the author is careful to point out that there are criteria other than sheer strength, such as speed and esthetics that are considered in joint selection.:)
That surprised me, but it makes sense as they explain that the glue faces of the half lap and bridle joints get clamped, whereas a M&T joint though squeezed up does not actually get any clamping on the glue faces.
But the detail that always worries me is how tight a M&T should be for optimal strength? If the side pressure of clamping a half lap or bridle is important, the side pressure created within a M&T by the tightness of fit must be highly relevant. I have varied between "tap in with a mallet" and "slide in neatly without it rattling" but I have never come across any actual test comparisons of goodness of fit.
Can anyone clue me in please?:?
(Note, dowels, dominos, and biscuits were okay for most applications but when they failed it was usually the stile that split down the grain at the point where the dowel or domino ended. The implication here is that for strength make your dowels, dominos, biscuits, and floating tenons as long as you can.
It is a good article and the author is careful to point out that there are criteria other than sheer strength, such as speed and esthetics that are considered in joint selection.:)