Roubo Workbench Leg Joint

[Stanley Covington]

Those of you that are considering building a Roubo style workbench, and have some skill with saw and chisel, might find the unusual dovetail joint in the attached diagram an interesting alternative for attaching the legs. Appearance aside, it has the advantage of assembling a little easier than the Roubo joint.

Stan

[george wilson]

We used a joint like that on our workbenches in the museum,except the angles were straight so as to not be cross grained on the rear tenon. Lost the tricky "dovetailed effect" on the front edge of the bench,but made a stronger joint.

[Jim Ritter]

I'm not sure how you would be able to assemble all 4 legs when stretchers are attached.
Jim

[Stanley Covington]

I'm not sure how you would be able to assemble all 4 legs when stretchers are attached.
Jim

You got me there.

[Jim Palmer]

I'm not sure how you would be able to assemble all 4 legs when stretchers are attached.
Jim

Sprung mortise and tenon joints.

[mike holden]

Still leaves the main problem with this joint. Wood movement. The legs will be prominent in the winter, sunken in the summer. Two weeks out of the year they will be level, one in spring, one in fall.
Blind mortise and tenon is still the best, although not as "cool".
258309

[Jessica Pierce-LaRose]

I believe this is the leg joining method Roy Underhill uses in his "French Work Bench" episodes from the 2007-2008 Woodwrights shop season. I believe he used angled legs with simply tenons for the back legs.

[ian maybury]

Guess the other consideration with a traditional Roubo is that widthwise movement in the top with long grain stretchers means that (a) the leg to top joint can't always be square, and (b) whatever joint is used (if it's of the broad format were the leg is let into the top) will have to handle a degree of angular movement - crosswise that is....

ian

[Tom Vanzant]

Chris mentioned that somewhere...

[Stanley Covington]

Still leaves the main problem with this joint. Wood movement. The legs will be prominent in the winter, sunken in the summer. Two weeks out of the year they will be level, one in spring, one in fall.
Blind mortise and tenon is still the best, although not as "cool".
258309

I must agree. I posted the diagram because it thought it is an interesting joint, not because it is the most practical. Beside the assembly issues if the same joint is used for all four legs, the cross-grain problem with the interior tenon significantly weakens the joint in reaction to the forces from a leg vise. So I strongly discourage anyone from actually using this joint for a leg that is part of a leg vise.

On the other hand, the Roubo joint has some problems too. With the exception of the leg supporting a leg-vise, it is overkill in light of the thickness and weight of the benchtop. And a through tenon has the shrinkage problem you mentioned. While the Roubo joint looks cool, it weakens the forward-most lamination in the top, and compromises the effectiveness of the leg vise by potentially creating a step at the face of the leg vise (same forward-most lamination). A better and stronger solution, in the case of a leg vise, is a double tenon instead of an exposed sliding dovetail tenon. This way one has a full-width, uninterrupted, full strength, lamination at the benchtop for the leg vise to act against.

But since cool is the obvious point of the Roubo joint, I thought "why not go one step further and use a truly interesting joint?" Ergo, the diagram. But don't actually use it!

Stan

[Stanley Covington]

Here is a pic I found of the joint in use, but not on a workbench. Very attractive IMO. Stan

258349

[Mike Brady]

I didn't see this mentioned in any of the above posts, but Chris Schwarz had a large chunk of his bench top, outboard of the dovetail, break off during use of the bench ( by Roy Underhill) at WIA. Depending on time of year and the snugness of the fit, that portion of the top would be inherently weak on all four corners. A vertically laminated top would be less-so, since the glue line would interrupt the shearing forces present in a slab top like Chris's cherry one.

[Jessica Pierce-LaRose]

http://www.popularwoodworking.com/workbenches/schwarz-workbenches/recovering-and-repairing-after-woodworking-in-america

Sounds like a lot of that was poor wood choice on his part. Although seeing how close he has his dogholes to the edge, I'm not certain I'd put a holdfast in those holes even if the wood was spot on.