Roubo joinery.........

[Peter Scoma]

I recently finished the base of my relcaimed white oak roubo but keep going back and forth as to how I want to join the top to the base. The stretchers and legs are connected with drawbored M&T's which I suppose would be sufficient for the top, however, I keep feeling as though I'm taking the easy way out by diverting from the traditional roubo's double tenon (1 squared off and 1 cut as a large dovetail). I must have gone back and forth 6 times thus far and need to make a decision soon. Many of you are probably familiar with the passage in Chris Schwarz's book where he talks about questions like this being essentially rhetorical. He basically says that if you are trying to rationalize making something less complicated or less robust, you already know that you shouldnt, and essentially have the answer to your own question. I suppose my greatest concern with the double tenon is the difficulty of cutting the joint. The oak that I am using is over 100 yrs old and hard as nails. I'm also working in a 9x10 ft shop which will make cutting and fitting these joints more difficult. Even chris has described the double tenon as a challenging joint to cut, particularly paring a perpendicular tenon in a 4 inch workpiece. So, I dont know, what are your guys thoughts on this dilemma? If I dont cut the double tenon I'll be using a drawbored M&T.

[David Kumm]

I used the drawbored M and T on mine but rationalized I was avoiding dealing with end grain on the top when flattening in the future. The traditional joint looks the best- if well fit- but the drawbore fits so well and makes for such a solid attachment that it is the more functional long term joint. Maybe I'm still rationalizing. Dave

[Randy Bonella]

+1 on the draw bored M&T for my Roubo. It was enough work just getting my reclaimed doug fir cleaned up, squared and parallel, not to mention that I really needed the bench done and spending even more time to get that set of cuts right just seemed but bit to much this go around. Maybe in a future bench for the double tenon.

Randy...

[Carl Beckett]

I am generally concerned when putting through joints into a top surface. Maybe not a rational concern - so others can jump in here and tell me their direct experiences.

But my concern is one of expansion and the mismatch in grain direction. You have a laminated top surface running horizontal grain, and then you put a through tenon (or dovetail or whatever) that the grain is running VERTICALLY - and at a right angle to the tabletop grain.

So when the wood shifts - either contracting or expanding - you get a different expansion rate on that vertical piece because wood expands more across the grain than with the grain.

So the places where the end grain comes through to the top surface - you will get a different height. You could never really flatten it because due to the seasons and humidity shift it would always be a little high or a little low.

???? Anyone have thoughts on this?

(I used draw bored M&T on my bench - to answer the question more directly)

[Jacob Mac]

I used the draw bore method and it has worked just fine. I used a lot of hand planes on the bench and never had a problem. If you are simply looking for function, I think the draw bored M&T is perfectly adequate.

[Peter Scoma]

Thanks for the feedback everyone.

Carl, you definitely make some valid points against using a through tenon. One of my major concerns is the joint opening up with seasonal change since it will likely just be a pressure fitted joint and not pinned in any way. The roubo obviously relies heavily on the strength of this joint since there is no apron. After considering the replies in this thread I think I am just going to go with the drawbored M&T.

Thanks again
PJS

[Salem Ganzhorn]

By the way this joint should not be under any strain in use. Some well respected bench designs just use a few dowels to register the top on the base.That being said I love the look of that joint!

Salem

[David Giles]

I pounded the leg tenons into the top mortises with a sledge hammer, plugged up those silly drawbore holes and it hasn't moved since.