There are many resources to draw from when designing a workbench, and I have enjoyed researching various bench styles and features. The basic design I settled on might be called a “Roubo-Style Hybrid Split Top Bench.” I am using the same hefty legs, support, and top that Roubo used in his bench. One of the features that intrigued me about Roubo’s design was its through dovetails joining the legs to the top. From his drawings, it appears that there is a full square tenon and a dovetailed tenon on each leg. Click on the drawing for a larger view.
I put a lot of thought into how this joint was constructed. The legs on his bench were probably solid, and tenons were cut by hand. I have laminated the legs on my bench. This was out of necessity, since I have no access to large timbers, and it also allows me to construct the tenons more easily.
Each leg is composed of 4 pieces of ash finished to 1 – 1/8″ thick, for a total leg thickness of 4 – 1/2″. Likewise, the first 4 laminations of the top is made up of 1 -1/8″ stock as well, so I can construct the joints individually.
The tenon that is in plane with the edge of the top is dovetailed, which acts as a wedge to hold the top side to side. The outer band of the top will be made of walnut, to provide contrast, and to highlight this joint.
I wanted the second tenon to hold the top down. My idea was to create a keyed, or splined dovetail tenon. I have never seen a joint quite like this, but I am sure someone has come up with it before. I constructed a mock-up as I designed the joint, so I could see how it would work. Once the splines are dropped down between the leg and the top, it creates a locking joint that holds the top down and will keep it there. I will use walnut again to provide contrast with the ash.
Roubo’s workbench had a “leg vise” with a large wooden screw to open and close the vise jaw. I have incorporated a leg vise into my design as well, but with a modern twist. While the vise will open and close using a massive wooden screw, the bottom of the vise jaw will ride on a 30 mm stainless steel rod traveling through a linear bearing. The wooden screw is 2 – 1/2″ in diameter, and came from Lake Erie Toolworks. The stainless rod and linear bearing came from Amazon. The idea for the linear bearing came from a post on “The Wood Whisperer,” Link: http://www.thewoodwhisperer.com/articles/roubo-workbench-leg-vise-alternative-linear-bearings/
One feature that I debated back and forth — round bench dog holes, or square? After giving it much thought and researching what others say, I chose to use square dog holes, or actually, rectangular ones. I will have a row of dog holes on each side of the bench. There will be some 3/4″ round holes in the top as well for hold downs, etc. Using a laminated top also made cutting the dog holes much easier. I used a router to cut the hole, angling the cut at about 2 degrees toward the direction of the tail vise. The hole on top is 1″ x 1 – 1/4″, and tapers down to 1″ x 1″. I plan to keep a dog in each hole, which can be popped up into use from under the top.
With the top of the bench being so massive, and with it residing in a shop that is not climate controlled, I knew that there would be seasonal movement of the wood. By laminating the top, the effect is to have the grain going up and down rather than side to side, almost like quarter sawn wood. This is the direction that is most stable, and moves the least. Rather than using one continuous slab, the top will be two pieces with a gap in the middle. And, I will use unglued splines at the ends of the top to hold alignment but allow the wood to move.
With the base glued up and the top coming together, here is an overall view of this workbench in progress. It is beginning to take shape!