# Mortise and Tenon Joinery

Traditional mortise and tenons, like most wood joinery are cut with saw and chisels (possibly with a suitable plane as well) and have sharp linear features which are not easily replicated on a CNC with a round endmill.

One technique would be to cut the mortise with the part flat on the wasteboard, and the tenon held at a 90 degree angle in a vertical fixture, rounding it to match the radius of the pocket used to cut the mortise. See the chapter on [Fingerjoints ](https://willadams.gitbook.io/design-into-3d/fingerjoints)for a fixture and the mechanics of doing thus.

An alternative which could be cut in a single setup would be to cut the tenon in two halves each laid flat on the wasteboard and rounding them using a cove radius endmill as used for the [Radiused Fingerjoints](https://willadams.gitbook.io/design-into-3d/radiused-fingerjoints) of the previous chapter. The mortise would need to be similarly rounded to fit, or one could relieve the shoulder using a V carving.

## Full Thickness Tenons

A more expedient option is to use the full thickness of the stock for the tenon thickness and to cut the mortise with dogbones or tees, possibly using a cove radius endmill or a V carving to round off the mortise to allow the parts to fit snugly. It is this option which will be explored here.

When the stock has a tenon cut while flat the tenons will have a rounded base which will need to be adjusted for when cutting the mortises:

![Tenons cut from flat stock.](https://235206304-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-M2NwCQrLAFxezOUTC9_%2F-MVsDWS8UV7vcl4ODbSB%2F-MVsi9Rg1Jq7mBkbMZkZ%2Fimage.png?alt=media\&token=82a8b7e6-0219-41aa-b084-8f9c1ac52bf1)

When cutting the mortises it will be necessary to cut T-bones or dogbones to allow for the square corners, and the longitudinal edges will need to be relieved, say with a V cut.

![Mortises relieved with a V cut.](https://235206304-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-M2NwCQrLAFxezOUTC9_%2F-MWBzBdRau2JWkvuvJrj%2F-MWCHpXfQ22BRXceBwcg%2Fimage.png?alt=media\&token=ea7e426b-7830-4062-bd03-36f57dfd28e6)

With code in place to make the mortises and tenons, it is a simple matter to use them in a suitable design:

![Child's step stool made with mortise and tenon joinery.](https://235206304-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-M2NwCQrLAFxezOUTC9_%2F-MWak9zHYOCzfkZ2ZkNH%2F-MWamd_z8AlMlw-pwi9r%2Fimage.png?alt=media\&token=05c94f17-7400-4a0b-ad66-6cc2baa5f399)

Available at: <https://www.blockscad3d.com/community/projects/1151153>

Arguably, the proportions should be adjusted, since the current dimensions seem more bench-like and is a bit low for use.

![Child's step stool with visible mortise and tenon joinery](https://235206304-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-M2NwCQrLAFxezOUTC9_%2F-MWasAayHuzVhmPcZkfO%2F-MWasHwgI7fcuBkMPyri%2F20210303_163038%5B1%5D.jpg?alt=media\&token=ea862822-3cb3-4e4b-a39c-53daa4cdf89c)

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