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Fifth leg que

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  • #143380
    Richard Guggemos
    Participant

    I’m considering whether to add a fifth leg to my workbench. This is probably overthinking, but would appreciate insights based on your workbench experience.

    First about the design. The top is 3-1/8 inches thick and 66 inches (5-1/2 feet) long, made from alternating strips of fir and cedar. The tail-end legs are 6″ from their end, providing clearance for the small vise located there. The head-end legs are located 3 inches in from their end, giving clearance to mount clamps on the end of the bench. The main vise is located immediately to the right of these legs (it’s a right-handed bench like Paul’s).

    I assume that any heavy chopping will happen on the top, not in the vise. It seems to me that this is likely to occur to the right of the vise (when facing the vise). So my question is: would it make sense. I imagine it would make this area more rigid, but will I notice a difference?

    Please share your thoughts.

    Cheers,

    Rick

    #143381
    David Perrott
    Participant

    I didn’t quite follow the description and not to be a jerk but…. If the historical record hasn’t found examples of this workbench, there probably is a reason why.

    #143382
    Larry Geib
    Participant

    I built a Tage Frid bench in 1976 within weeks of Fine Woodworking #4 hitting the stands. It has five legs.

    Still use it.
    Is that historical? 😉

    • This reply was modified 2 years, 11 months ago by Larry Geib.
    • This reply was modified 2 years, 11 months ago by Larry Geib.
    #143388
    David Perrott
    Participant

    Definitely! I want one of those styles. Popular woodworking is coming out with an article on a new version of it. That’s not what he is talking about though.

    #143390
    Ed
    Participant

    Isn’t the 5th leg on the Frid bench because of the vise, not because of the main top? See, http://s3.amazonaws.com/finewoodworking.s3.tauntoncloud.com/app/uploads/0000/01/05192729/011053062_mdsq.jpg.

    Paul’s 4-legged bench worked fine for me.

    #143391
    David Perrott
    Participant

    Yes. It makes the vise.

    #143393
    mxbroome1
    Participant

    I would say build it leaving room for the extra leg. Use it a while and see if you want to add it. My guess is not unless you plan to use logs or other really heavy work that needs the extra. I built my bench prior to finding the Paul Seller’s site and my bench is not as robust as his but still is plenty solid for furniture and cabinet work.

    #143394
    Richard Guggemos
    Participant

    Thanks to everyone for their input.

    It would have been clearer if I explicitly stated that I’m essentially building a Paul Sellers model bench.

    My description was intended to clarify the position of my legs, and my front vise to same. Further, that as a result, the primary spot to chop mortises will be cantilevered out About a foot from the nearest leg.

    So my question really comes down to the stiffness of the top. If you’re chopping into a heavy dense wood, do you find yourself migrating your work to a position over a leg, or do you find the top Sufficently rigid such a situation?

    Naturally, I can leave space for an extra support. But I’d probably want to use a lower spreader to better connect it to the nearest corner. My skills aren’t really adequate to cut a mortice on the existing leg in place, hence my desire to make a decision now.

    As to historical record, I’m in favor of it. But, respectfully, I think it’s blind to be a slave to it. The record is necessarily incomplete. And while I’m probably not genius enough to have the next great idea, it seems obvious to me that anything can be improved upon. Finally, I think that we can all agree in the importance of a solid surface when chopping, and that this importance grows as our material gets denser and harder.

    So does anyone have any further input?

    #143395
    Hugo Notti
    Participant

    How about adding aprons? They will spread the support of each leg.

    And do chop near the top of a leg (Newton, action/reaction, vertical grain kicks back much better than air). It is not the surface that counts, but the support. You can have a 3/16″ plywood benchtop, if you are chopping right above the leg.

    If your room has a wooden floor, look for the beams underneath (tap with a wooden mallet and listen) and position the “chopping leg” near or even on top of one. With heavy legs, this is less important for good chopping but quite important for less noise and it is nicer to the wooden floor.

    Of course, a fifth leg can’t hurt, if you want to have your chopping area elsewhere. But then you will have to match five legs to level, both, on the bench-top and on the floor, which is hardly ever perfectly even.

    Dieter

    #143397
    Larry Geib
    Participant

    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.)

    Paul chopping in oak

    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 2 years, 11 months ago by Larry Geib.
    • This reply was modified 2 years, 11 months ago by Larry Geib.
    #143486
    Richard Guggemos
    Participant

    Hugo, thanks for your input.

    Larry, thanks for the analysis. Lots of good info there and I’m going to have to read it 2 or 3 times to pick it up. That said, it adds a comfort factor to my thinking. So no fifth leg for me.

    Cheers

    Rick

    #143747
    Larry Geib
    Participant

    If you think you need further validation, PAUL addressed your concerns in a discussion of his small joinery bench, including top stiffness on the
    2 3/4″ dimension he used.

    Thoughts on Small joinery workbench

    Enjoy your build.

    • This reply was modified 2 years, 11 months ago by Larry Geib.
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