Hi,
I have build a bunch of this type of step stool https://www.finewoodworking.com/videoworkshop/2020/05/virtual-workshop
I have wondered about this type of joinery and wood movement. If you scale this construction up, say for a bench, would there be a problem with wood movement between the mortises? I guess you could keep the mortises a bit closer to allow for movement in the width, but then you get a bigger risk of cupping, since the tenons are not keeping the board flat as effective. Better off with sliding dovetails on bigger pieces?
Thank you for your thoughts and experience.
Replies
With the legs and top all running in the same direction the wood movement should not be an issue. The only place there is cross-grain movement would be the stretcher. If it were scaled up you might want to go from a single mortise for the stretcher to a double mortise arrangement like for the legs/top connection to minimize the amount of expansion in a single mortise to keep it from breaking out the thin part at the very top of the stretcher. On the whole I think it would scale up without issue.
I agree, this will scale without issue
Thank you for your answers.
One more question; how strong would a loose tenon/domino joint connecting the legs to the top be? There is not much long-grain to long-grain glue surface, so I have a feeling that this will fail over time?
Your feelings are on target, but the "stresses" on the leg-to-top joint are pretty much from picking it up to move it around. When in use the joints are being compressed; gravity is working for you.
With all else the same, (and with the stretcher glued to the underside of the top) you should be fine. If you were to swap in dominos for the leg-to-stretcher joints I'd be more concerned.
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