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Thread: Wedged Tenon - 21st Century Workbench

  1. #1

    Wedged Tenon - 21st Century Workbench

    I am contemplating two different "knockdown" joints for the stretchers on a 21st Century Workbench inspired design. The two bottom stretchers in the original design have a type of wedged tenon that I really like (first pic below), but I have never seen before, unlike the "Stickley Type" wedged tenons (2nd pic below) that are used/seen quite often. Is one significantly stronger than the other? My suspicions is the Stickley type is both stronger and easier to cut.

    I appologize if my terminology is off, I don't know how else to describe these tenon joints.



    Stickley Type:

  2. #2
    Join Date
    Oct 2008
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    Hey Scott, welcome to the Creek!

    I am also building the 21st century bench right now and have also put some thought to those wedged lower rails. I was contemplating changing the lower rail joints to be exactly like the upper rail joints to remove interference between the wedge and a set of drawers I planned for the interior of the bench. However, I have decided not to put in the drawers in lieu of room to store bench jigs, etc. I did decide however to beef up the lower rails and upper stretchers to be the same dimension as the leg and lower stretchers. My lower rails will dovetail into both halves of my legs and my wedges will be twice as thick as those in the article.

    Anyway, in this application IMHO, the wedged dovetail joint is a stronger joint than the Stickley type wedged tenon because the dovetail is an interlocking joint and will offer more resistance to racking forces such as hand planing towards the end of the bench. As the wedge is driven in, the lower rail is seated into the dovetail. The shoulder of the lower rail is locked against the leg by the dovetail when racking force is applied. With the Stickley wedged tenon, the mortised joint itself offers no support against the racking force so the racking force will move squarely against the wedge itself which is made of much thinner stock than the leg. Having said all that though, I think that most of the racking force should be directed at the joint of the upper rail, which I assume you would leave as originally designed. So, it may be that the Stickley joint is sufficient for this bench.

    My $.02 worth,
    Brian

  3. #3
    Thanks Brian. That makes perfect sense! More surface area under pressure from the wedge = stronger joint.

    I eventually want to include a set of drawers, but I'll just work around the wedge. I haven't decided on the location of the upper rail yet. I either need to keep it much higher than the original design to accommodate the drawers, or perhaps, do just one larger upper rail on the back...

  4. #4
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    Quote Originally Posted by Scott Climb View Post
    Thanks Brian. That makes perfect sense! More surface area under pressure from the wedge = stronger joint.

    I eventually want to include a set of drawers, but I'll just work around the wedge. I haven't decided on the location of the upper rail yet. I either need to keep it much higher than the original design to accommodate the drawers, or perhaps, do just one larger upper rail on the back...
    I thought about moving the upper rails and also going with a slightly narrower rail to gain more drawer space too. But then you have to consider the height of the chops on the face vise to keep clearance. In the end, before I ditched the drawers entirely, I was leaving the rails in the original spot and was just going to settle for shallower drawers to fit the opening. I might still put drawers in at some point in the future. I suppose I could just trim the end of the wedges to clear the drawer fronts.

    Currently, I'm thinking about adding a second shelf supported by the upper rails, just like the shelf supported by the lower rails. I have a small shop so I tend to try to figure out how to use all available space. The space behind the upper rails is kind of wasted. I'm thinking I can slide my long bar clamps in from the end on that upper shelf, solving not only my clamp storage problem, but also adding quite a bit of weight to the bench.

    Good luck with your bench. Hope it doesn't take you as long to build as it is me. Working on it only on weekends, and part-time at that. It has been my only project this winter. I have all the lamination work done, and all parts are cut to final dimension. Hopefully I can start cutting joints this weekend.

    Brian

  5. #5
    Join Date
    Jun 2007
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    Half Moon Bay, CA
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    I have heard that joint called a sage-kama, David Fay used it in a bed of his:
    http://www.davidfay.com/Articles/95.fall.hf.php Apparently a traditional japanese joint.

    -Josh

    racking motion, bed... what?
    Last edited by Joshua Layne; 02-12-2010 at 12:11 AM. Reason: grammar
    >witty woodworking quote goes here<

  6. #6
    Very cool. Thanks for the additional info about that joint. Looks like a fun one to try.

  7. #7
    Join Date
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    I've found through bad experience that removeable wedges work better if gravity helps keep the wedge in place -- that is, if the wedge inserts downward. If the wedge inserts horizontally, it tends to loosen up. I think the issue is that wracking forces on the furniture can loosen up the wedge, and then it just continues to get looser. However, the vertically-inserted wedge will tighten back up as those wracking forces get applied and removed. I've seen this issue on a bed. I'm sure the problem would be even worse on a workbench.

  8. #8
    Thanks Jamie. I am getting close to having to make a decision on what joint to use. My requirement for the joint is that it is non-permanent, so I can break it down if needed. I am stuck between using lag bolts (simple, very effective) and this sage-kama joint which would be fun to do and look great, but I am unsure of exactly how effective it will be in this application.

    If anyone else has experience with this type of joint please chime in.

  9. #9
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    Quote Originally Posted by Scott Climb View Post
    Thanks Jamie. I am getting close to having to make a decision on what joint to use. My requirement for the joint is that it is non-permanent, so I can break it down if needed. I am stuck between using lag bolts (simple, very effective) and this sage-kama joint which would be fun to do and look great, but I am unsure of exactly how effective it will be in this application.

    If anyone else has experience with this type of joint please chime in.
    Lag bolts are practical, easy to do, and are difficult to screw up. Wedges are elegant, take more work, and can be as sturdy when done properly. I'd consider using lag bolts on shop equipment, but never on fine furniture. If you think of your bench as closer to fine furniture, perhaps wedges would be the way to go.

  10. #10
    Quote Originally Posted by Scott Climb View Post
    My requirement for the joint is that it is non-permanent, so I can break it down if needed. I am stuck between using lag bolts (simple, very effective) and this sage-kama joint which would be fun to do and look great, but I am unsure of exactly how effective it will be in this application.
    I would actually suggest embedding a nut in the stretcher rather than use a lag screw. You can use fancy "bench bolts" from LV, but I just used a standard 6" long 1/2" bolt with a hex nut and washer in the stretcher. Much more secure than a lag screw, since there is no risk of stripping out the threads.

    Alternately, you might consider a tusk tenon. This is similar to the sage-kama but the wedge is vertical. Here's an example from Peter Follansbee's bench:


  11. #11
    When I designed the bench, I copied the detail from an illustration of a Nicholson bench. The same joint is used in Japan, so maybe it was a Nicol-san. Anyway, I wouldn't use a Stickley style tusk tenon in this situation. The tenon on the end of the bottom rail is half the thickness of the rail, about 7/8". This was done to keep the outer face of the rail flush with the outer face of the leg. The orientation in Follansbee's bench is workable, but it would make me nervous to remove that much stuff from the rail for the mortise. Peter knows his business though, so if that's what you're after, that's the way to do it.

    The whole idea of wedging these joints is the ability to reach down and whack on the wedge to tighten the joint if it were to work loose from shrinkage of the wood or the repeated force of working on it. It also is instantly removable if you need to disassemble the bench. As far as difficulty goes, I think my way is easier, I cut the tail in the end of the rail and the socket in the leg, and fit the wedge before I laminated the two parts of the leg together. Seeing what you're doing makes most things easier.

    There is a SketchUp model of the bench in the Popular Woodworking collection on Google's 3D warehouse, if you want to take a close view of how the joint works.

    Bob Lang

  12. #12
    Bob how long have you been waiting to use the "Nichol-san?" Good one.

    I've been studying and measuring your design in Sketchup but I never thought about cutting that mortise before glue up (and I was just about to glue up my leg stock). Now I'm convinced I can get it right. I was apprehensive about the strength of the joint and about getting a good fit having to chop the mortise at an angle. Of course, the strength of the joint goes up as the fit improves. Thanks for the advise. I'll be sure to post pics as the project progresses.

  13. #13
    I thought that was obvious, as it was mentioned in the article in the October 2008 issue of Popular Woodworking and in the video. If you go to the Pop Wood editor's blog and search on "Bob's Bench" there are several entries about the build and a picture of the joint before assembly.

    You can also reach me (or any of the editors for that matter) by e-mail if you have any questions about anything we print. Our addresses are in the Masthead of the magazine and at the "Contact Us" link at the bottom of our web pages.

    Bob Lang

  14. #14
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    Bob,

    I'm curious if there would anything you would do differently in building the bench now that you've been able to use the bench for a year and half or so?

    BTW, I think it's a great design. Took me a while to get on board with the split top, but I'm pretty sure I'm going to really like that when I get my bench finished.

    Thanks, Brian

  15. #15
    I hadn't seen the magazine article or the blog - just the video. If I had, your right, it would have been obvious. I was mostly just hung up on the joint, now I'm sure I can get everything else I need from the Sketchup design. Thanks so much!

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