The pocket hole screws did not break or fail the wood between them failed. Mattias screws two pocket hole screws into each side of the bracket (muttering that he hates pocket holes) and sets the bracket up on the testing pole. He cuts down the double-tenon shelf bracket to make a pocket hole joint. The wood also broke away from the screws, so again, utility-grade lumber is sub-optimal for structural brackets. He used washers to slow that movement, but it did not stop the movement.
The failure was as he suspected it would be, in pulling the screws through the wood. The screw-joint shelf bracket easily held the necessary weight at the end of the one-foot bracket, only failing when he stepped out on the extended portion. Screwed-together shelf bracketįour-inch screws with washers on the heads hold the two pieces of wood together. Mattias suspects with a better grain choice the tenon could have held twice as much weight. The wood grain on the tenons was not ideal for mortise and tenon joinery-it was a utility-grade 2x4, not white oak. The bracket appears to have failed at the joint: the tenons pulled out of the mortise. Upon further inspection, the tenons broke along the bottom, allowing the top to pull out. Double-tenon shelf bracketĪ double mortise and tenon joint is cut into the framing lumber, and the joint is assembled. Next, he steps out further from the pole to see when the bracket will fail. Of course, it is strong enough, so he extends the bracket length by clamping a 2x4 to it. He clamps the shelf bracket to a pole in his garage and stands on the bracket. First, he tested a double mortise and tenon joint against two four-inch screws angled downward. Mattias made some shop-grade shelf brackets out of off-the-shelf 2x4s to test joint strength. He sets out to discover which shelf bracket is more substantial, a double-tenon mortise-and-tenon bracket or one held together with a couple of long wood screws? If you know anything about Mattias, you know he likes to make stuff from wood. It looks like Mattias Wandel needs some shelving for his shop.
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