Chris Schwarz's Blog

3 Tips for Wedging Your Joints

3 Tips for Wedging Your Joints

Wedging joints adds great strength, but it also is risky. A wedge can split the work, it can fail to dive into the tenon (sometimes popping out of the tenon), or the tenon itself can split when you hit it, making a mess of things.

Here are three things I do to reduce the risk.

1. Make lots of wedges. When I make wedges, I usually make at least 100 so I have lots of them on hand at assembly time. Every wedge is a little different. You might need a thin one for a tight tenon or a big fatty to close up a big gap. I like to make my wedges so they have a 4° included angle at the tip.

2. Add a secondary bevel to the wedge. Right before I drive a wedge home in a tight tenon, I use a knife to carve a quick secondary bevel on both faces of the wedge. This secondary bevel helps start the wedge in tight spaces.

3. If the tenon is still too tight, open it with a chisel. Sometimes even a perfect wedge will fail to open a tight tenon. So I help things along with a chisel. Take a chisel that is the same width as the diameter of your tenon and use it to split the tenon open above the surface of the work. This almost always does the trick.

Last of all, use hide glue. It’s reversible so if you really muck things up, you can apply some heat and moisture, take the joint apart and try again.

— Christopher Schwarz

9 thoughts on “3 Tips for Wedging Your Joints

  1. Jdefeo

    Hi Chris
    Your tip on wedging tenons is quite helpful I will use when making windsor rockers which I love to make, but my question is about an article you wrote a few years back using black bison wax as a finish. I have used the technique on several of my projects with great results and i am about to use it on a kitchen table I am making for my daughter. The question I have is … after 2 coats of wax will this be enough to stand up to a kitchen table versus 3 small children?. Should I or could I add another finish on top of the wax for more protection?
    Any suggestions would be much appreciated.
    Thx
    Joe

  2. Straightlines

    In order to prevent split tenons, I’ve successfully used Tage Frid’s technique of drilling an 1/8″ hole along the base of the saw kerf.

  3. slanctin

    Hi Chris,
    I have a question unrelated to above but am hoping you can help–i’m sure you can!
    I am a (very) novice “woodworker”, if i can be allowed to use that word–might be more appropriate to say i have an interest in woodworking and am looking to develop my skills. My complete works so far consist of an adirondack chair that turned out pretty decent.
    Anyway…my next project is a workbench, and right now i’m thinking Roubo type. I’m unsure I’ll be able to find a large enough slab for the bench top, so am thinking i will have to glue up a slab. i like the look of the through tenon to attach the leg posts to the top. This may be a naive question, but am wondering if that can be done with a glued up slab or if i should find another way to attach the top to the leg posts, and if so which would you recommend?
    Thank you for your help.
    Sam

    1. Christopher SchwarzChristopher Schwarz Post author

      Yup. You can do this with a glued-up slab. In fact, a glued up slab can make it easier – you can leave spaces in the laminations for the tenon and sliding-dovetail joinery. I’ve done this many times when building workbenches in classes.

      Just use inexpensive framing lumber (yellow pine or Douglas fir) and make the joints on the legs match the thickness of the laminations.

        1. drjohn1963

          Chris’s workbench book is excellent and a great help for building such a bench. If you are going to invest the time and energy to make the bench, then the extra couple of bucks for the book is an excellent investment. His books and the Hand and Eye books are among the best woodworking books I’ve read.

          1. JasonS

            I agree. Can’t recommend that book highly enough. I was originally looking at making a Roubo type too, but changed to the knockdown Nicholson. Just finished it up this weekend. Its awesome and I’m glad I went that way instead of the Roubo. Very robust bench that I can take apart and store quickly in my small shop.

  4. Spoiler

    These 3 tips are helpful to me. Could you comment further…
    Since reading ADB I have made 4 projects with staked legs. The Veritas tenon maker/ reamer bit combo is awesome.
    After verifying that all goes well with the dry-fit, I have used a .015″ dovetails saw for the kerf, a thick kerf band saw and a really thick kerf panel saw. All work and look a little different. Is there a kerf width that represents “ideal” for strength.
    Also- the tenon pictured above looks to be proud of the seat about 1/4″ but I have seen tenons with wedge standing 1″ proud or more.
    Is this simply a case of whatever I feel like doing at the moment or are there logical reasons for doing it one way or another. Thank you.

    1. Christopher SchwarzChristopher Schwarz Post author

      Good questions.

      When kerfing tenons, I choose a saw based on how tight things are. In typical chairwork, a tenon saw is my saw of choice. But when I make big tables, I’ll switch to a handsaw or even a band saw at times. This requires some judgment. If the joint is really loose, use a thin saw. If it’s really tight, use a thicker one.

      As to how much tenon to leave above the surface, I shoot for 1/8″. What is shown in the photo above is about 1/8″ and a little more. Anything more and the tenon will resist your every effort to get the wedge below the surface.

      Hope this helps.

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