In Tricks of the Trade

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I well remember the day when I couldn’t get a mortise-and-tenon joint to come together no matter how hard I tightened the clamp. I had ignored a fundamental rule: Always make mortises 1/16 to 1/8 deeper than the tenons.

There are two reasons for doing this. First, you don’t have to obsess about marking a perfectly smooth bottom in the mortise, which saves time. Second, space is needed for excess glue. This was the reason my joint didn’t go home. The tenon had a tight fit on all four sides. Too tight, really. It had pushed all the glue to the bottom of the mortise. A deeper mortise would have given the glue space to pool and allowed the tenon to go home.

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