Mitered Joint for L-shaped Table Top

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  • #640738
    sanford
    Participant

    I wonder if there is a more or less standard way to make this joint. I am making an L-shaped table top from white oak. I would like the boards to come together into a miter joint as shown in the attached diagram. It is obviously a weak joint and in need of support. But I am not sure how to do it while taking wood movement into account. The top will be 20 inches wide or so, and I assume that is wide enough for movement to be a problem. I thought about adding a spline the length of the miter, or using the tenoned miter joint Paul showed in one of his videos — if you have not seen Paul’s video, I have included a snapshot of one I experimented with a while back partly taken apart. But although those solutions work fine for a narrow joint, say for a frame, I am pretty sure that there will be problems with something larger. I assume I need something that will capture the miter joint and still allow movement.

    I am pretty sure there is a solution. Looking at L-shaped tables on the web, I see a lot of plywood tops, which would be an easy solution. But there are also pics of solid wood tops, and a few of those have wood arranged into the sort of miter I would like. Any help would be very welcome!

    #640742
    sanford
    Participant

    Oh, one other thing. I might be wrong about the examples I have seen on the web of this pattern of wood on the tops of L-shaped desks. I may just be a thin veneer on a piece of particle board or some such. I cannot tell from the pics.

    #641177
    YrHenSaer
    Participant

    Not difficult to do, but needs a bit more work than normal to ensure an effective and pleasing joint.

    If you are considering two sets of end grain boards that are the width of the top meeting at an angle in the middle, then think of the unpredictable amount of expansion and contraction where they meet over the seasons plus the difficulty of effectively joining the two together and it will be obvious that this won’t work well.

    The most reliable way to do it is to make the two independent table tops with the desired angle as normal, allowing enough overlay at the angled section to make up a tenon section to sit within a normal bread-board type table end. This will level up the angled section and give you a good grounding for attaching them together.

    It’s this B-B end that will give you a meeting joint that is long-grain to long-grain and you can build in enough lateral play for wood movement in the table top joint where it meets the cross boards as you would in a conventional right-angled bread-board end. Arrange and level the meeting point and measure on the edge, down from the top, the exact amount for a couple of locating dowels or splines so that the tops are level and remain level to your satisfaction. You can then dry-join them together with a set of brackets below or use draw bolts that can be dismantled if needed in the future. Aesthetics means that you’ll probably want to B-B the opposite ends as well….

    Hope this helps

    #641195
    sanford
    Participant

    Thanks YrHenSaer! So I guess the breadboard which joins the two panels will look something like the modified diagram I attached (I added two little broadboards to the ends for aesthetics as you suggest). Normally, you would glue the center tenon of a breadboard and leave the rest dry for wood movement, but you are suggesting leaving the whole thing dry. I assume that is to make it possible to take it apart. That sounds like a good idea though if I decided I did not want to take it apart, I could glue the central tenon and perhaps drawbore the thing. On the other hand, I like the possibility of disassembly.

    By “draw bolts” I assume you mean those little pieces of hardware used to pull countertops together. I never used them and had to look them up. They seem like a very good solution if I decide to go with a breadboard that can be disassembled.

    Thanks again. This is very helpful. I think I will try this using construction grade wood before trying it with my white oak.

    #641197
    YrHenSaer
    Participant

    Yes, That’s the idea.
    The B-B ends would normally consist of a sliding tongue on the board sitting in a groove on the end, held together with draw-bore pegs sitting in extended tenons. The centre one is fixed whilst the outer ones have an elongated hole to allow sideways movement.
    It is a standard table-end technique and if you search YouTube there will be lots of how-to vids which will explain better than I can here. Use the same technique on the outer ends,

    I’m assuming that you want the thing to be able to be dismantled in future. The draw-bolt brackets available for kitchens etc., may be too large, but the idea can be adapted to smaller pieces of metal or wood blocks.

    Good luck

    P.S. I omitted to say that Paul Sellers has a video on this site showing B-B ends on a cutting board: https://woodworkingmasterclasses.com/?s=bread+board dated from 2013.

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