Perhaps the most challenging aspect of the step stool project is the mortises that house the through-tenons. This is a part of the project where any sloppiness will result in big gaps on the outside of the case. Further complicating matters, I needed to transfer the location of the mortises from the tenons marked on the inside of each side. With no good straight reference surfaces to register against, there was no good way to transfer those marks around to the outside face with marking tools.
The real trick to good through tenons (or any through joinery like through dovetails or box joints) is starting with good square joints to mark from. In this case, that meant making dead straight and square tenons. But with tenons this wide and long, I couldn’t rely on my normal techniques to get the job done. Fortunately, I won a Bad Axe Toolworks tenon saw at this year’s Woodworking in America (I’ve been keeping this a big secret) and this big boy really came through for me in this episode.
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