Reply To: Fifth leg que
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Let’s see… my first impression is That if the stiffness of the top is what it comes down to for you, just build what Paul drew.
If your bench is to be 66″ and your Legs are least 3 1/2″ wide and 6″ overhangs, you only have a span between the legs of 47″. With wider legs, it’s even less. 3+ inches top thickness would be plenty stiff on an English style bench even if it is softwoods. Fir, especially, is plenty stiff. (You don’t mention what kind of cedar. Properties vary wildly )
Paul’s video series shows an 94″ bench, with a distance between the legs of 65″, about the entire length of your bench. And he shows a 2 3/4″ top thicknes – 3/8″ less than what you propose.
Even if you followed all Paul’s scantlings, your 66″ bench would be about 2.77 times stiffer between the legs than his video build for his 94″ bench.
The Western Wood products Assn. has all kinds of fancy formulas, but Stiffnes is proportional to the width of the top and Apron and the cube of its depth. ( and inversely proportional to the cube of free span)
A free span half as wide is 8 times stiffer.
Paul has all that worked out for you in his design. My advice is that for the smallish bench you contemplate you really don’t have to up-engineer what Paul has designed for you already, especially if you glue it together, although you then probably sacrifice portability. What you gain is unitary mass. A bench made of independent parts just bolted together will eventually rattle a bit. (Paul’s wedged leg idea looks to be a help, and I think he has you glueing the top to the apron).
I’d also consider slightly longer overhangs. Most of the benches I see, including Paul’s, show overhangs in the 1+’ range, though most benches are longer than your build.
<edit> Paul specifies a 9″ overhang here: https://paulsellers.com/2012/06/making-the-workbench-11/
That wouldn’t be too much even with your shorter bench. You will be working mostly towards the right of the vice.
If you are right handed, you might want to consider at least a longer left overhang – maybe even placing the vice just to the left of the leg so the leg naturally is in chopping position. But then you are deviating from Paul’s overall concept and would need more mass to make that work. If you follow Paul, you would work more in the middle of the bench ( a good thing).
For comparison, by Frid bench has a front Apron of about 4×4 and the rest of the top was built to about 2″ thickness for portability (in black cherry) It is only about 6″ longer than yours, and the span between legs is about 46″. I’ve used it for 40 years, now. The only time I try to chop over a leg is for large and deep mortises. And even then, it’s not a major inconvenience to move over to the right leg. ( 18″? — one step). The Frid/Klaus bench style has you working just to the right of the shoulder vice and left of the tail vice most of the time, and right in front of the shoulder vice for cutting dovetails. There are legs under both vices.
Paul stays in one spot a lot – also just to the right of the vice, but I suspect that is to make video. And he seems to have large vices, as he does lots of mortise chopping right in the vice. He seems to have no problems. So spend the extra for a sturdy vice if you wish to emulate him.
Here’s a screen shot of him mortising in oak right in his vice. Note he’s standing almost in the center of his bench.( it’s also a smallish bench.)
So you will have no problems if you follow his scantlings, as long as you get a big fat vice like he uses.
- This reply was modified 7 years, 9 months ago by Larry Geib.
- This reply was modified 7 years, 9 months ago by Larry Geib.