|Forum topic by MJCD||posted 09-24-2012 05:40 PM||1169 views||0 times favorited||11 replies|
09-24-2012 05:40 PM
I need some advice …
I’m working on a large, Jatoba-based outdoor bench, which has 40 M&T joints – most of which are load-bearing (there are backrest slats which are not). The bench will be 100 lbs, all-in; and will be permanently outdoors – North East, US.
This is my first M&T project, and I’m unsure of how tight the Tenons need to be in the Mortises – the M&Ts are already created, and within my tolerances, I have a distribution of spot-on to somewhat loose (not that I have experience in these definitions); I believe it’s correct to say that none of them are either catastrophically loose or too-tight for the epoxy glue.
I’m using the West Systems G/Flex 650 epoxy as the adhesive, and I’ve researched the product as having excellent holding strength (greater than the wood, itself) & flexibility – that is, it’s not brittle to where normal racking and wood movement will result in failure.
The Tenons & Mortises are all 1.25” deep by 0.75” thick, and vary in width from 1.75” to 2.5” – these are Integral Tenons, not floating. My concern is that someone will try to lift it bench by an armrest or a back rail (both of which I would peg), causing the joint to fail – that is, the glue, alone, on one or two tenons may not be able to support the sheering effect of lifting 100 lbs.
My thought is to peg the corner tenons at 0.25” above the tenon base, with a 0.25 peg, and to do this while the project is glued & clamped-up.
As always, I appreciate the experience and counsel from the Forum.
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