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  • Mortise to short?

    I'm building my first dining table, maple center with walnut edges and breadboards (I built a similar coffee table as my first run).  I'm concerned I may have made the end tenons too short. The table material is 1-1/2" thick...the breadboards are 7-1/2" deep x 3-1/2' long (the width of the table). The tenons are 1/2" thick by 7/8" deep (the current fit is nice and tight).  I can make them bigger but at the sacrifice of the table length, which I would prefer to keep as is (5'). I plan to put 1/2" dowels along the tenon/mortise line (glued center, wider holes on the ends and not glued). Am I overthinking this or do I need to make a deeper tenon/mortise?
    Thank you. Stephen
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  • #2

    Re: Mortise to short?

    If I read this correctly you are going to put a 1/2 inch wide dowel into a 7/8 tenon. If so then that won't provide the strength needed because there will not be enough surrounding wood in the tenon for support. A 1/4 inch dowel or more tenon width I think.
    smallerstick likes this.

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    • #3

      Re: Mortise to short?

      A picture would explain it far better than your words as I have no idea what you are meaning

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      • #4

        Re: Mortise to short?

        I'm with Bob, not sure what you are describing. I would expect tenons on the ends of the table top boards and a mortice in the breadboards, not sure where the dowells are going. 

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        • #5

          Re: Mortise to short?

          Maybe think of 3/8 dowels?
          Egon
          from
          The South Shore, Nova Scotia

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          • #6

            Re: Mortise to short?

            Originally posted by Doug G View Post
            I'm with Bob, not sure what you are describing. I would expect tenons on the ends of the table top boards and a mortice in the breadboards, not sure where the dowells are going. 
            I see I'm getting the same strange character A with and accent at the end of my post like some others are, not sure what is causing it?

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            • #7

              Re: Mortise to short?

              People keep telling me that....I make things too complicated... .  I also may be mixing up my terms...if I am...sorry for the confusion.
              Let me simplify my question....Could there be any issues with having a tenon only 7/8" deep?  Should the tenon be longer (and correspondingly...the mortise)? Forget the dowel part...not important (but I will make it smaller). Thanks for the help. Also seeing the A characters everytime I hit the Enter key...

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              • #8

                Re: Mortise to short?

                OK, what you are doing is clearer. Not sure if 7/8" is too short, sounds a bit short but don't have direct experience to allow me to comment with confidence. If it turns out to be too short based on input from others, you could cut the tenon off, cut a mortise and use loose tenons of sufficient length rather than shorten the table length. 
                Les Groeller and Dean like this.

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                • #9

                  Re: Mortise to short?

                  Are they haunched tenons? I have yet to build a table top, nor have I done breadboard ends before, but I have definitely read up on them. I think the general rule is 1/3 for tenon thickness and tenon length should be similar to the thickness of the top. 7/8" tenons with a 1/2" haunch would probably be appropriate for a 1.5" thick top.

                  1/2" pins sound a bit large for your tenons. I think 1/4" or perhaps 3/8" would be more appropriate, and I'm not clear what you mean when you talk about positioning them.. glued center and elongated outer holes (unglued) is correct (although if you know for sure the table will always stay against a wall you could glue one side and float the rest). You can try drawboring the holes as well to ensure a tight fit, although you'd want to make sure you had that process figured out before going for it!

                  I didn't read this article.. but it shows a good picture of the haunched tenon design, which I think is the best way to go if you want your table to remain as flat as possible.

                  https://www.woodcraft.com/blog_entries/breadboard-ends

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                  • #10

                    Re: Mortise to short?

                    I think the 7/8" tenon in a breadboard end would be sufficient. They primarily serve to keep the top flat. If you were talking tenons on an apron into a leg that needed to withstand racking forces the 7/8 would be too short.

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                    • #11

                      Re: Mortise to short?

                      The breadboard ends are 7-1/2" wide. For a table end I personally would be afraid that anyone leaning on the end of the table with only a partially glued 7/8" tenon holding the 7-1/2" extension would snap it off or bend it. I haven't made too many breadboard ends (mostly on cutting boards) but it seems to me that the minimum tenon length I've seen when researching designs that were for tables were about 1/4 the breadboard end width, so 7-1/4" would give a tenon that is at least 1-3/4" long. 7-1/4" produces a lot of leverage. Also, with a 7/8" tenon, even 1/4" dowels will be very close to the edges of the breadboards, and especially to the long grain of the tenon ends (5/16" away), which will produce seriously weak points.

                      I'm not saying you should make the tenons super long, they are fairly thick, but if I were you I'd make them at least 1/2" longer. It won't show over 5 feet.
                      Kayak Jim likes this.
                      Frank
                      SPCHT

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                      • #12

                        Re: Mortise to short?

                        Originally posted by EvilBeaver65 View Post
                        People keep telling me that....I make things too complicated... . I also may be mixing up my terms...if I am...sorry for the confusion.
                        Let me simplify my question....Could there be any issues with having a tenon only 7/8" deep? Should the tenon be longer (and correspondingly...the mortise)? Forget the dowel part...not important (but I will make it smaller). Thanks for the help. Also seeing the A characters everytime I hit the Enter key...
                        It sounds to me as if you mean a tongue and groove, not a mortise and tenon, if this is the case 7/8 is too much 1/2 would be enough, but as stated before a picture would clear up a lot of difficulties, and yes you are making it difficult, no picture.

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                        • #13

                          Re: Mortise to short?

                          Here is a photo of the joint I am talking about. To confirm....the tenon (tongue?) is 1/2" thick and 7/8" deep, the breadboard is 1-1/2" thick and 7-1/2" deep.
                          Attached Files

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                          • #14

                            Re: Mortise to short?

                            I think Frank's right. I was forgetting about the force of someone resting weight on the end of the table. I don't think I'd be comfortable with a tenon that short considering it's only glued in the centre section.

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                            • #15

                              Re: Mortise to short?

                              I made a table with breadboard ends years ago and moved it on to a neighbour's PEI cottage when we renovated the kitchen. Mine was based on the harvest table episode of New Yankee Workshop minus the under-table stretchers but incorporating a deeper apron with two storage drawers. It was a good, sturdy table but the red oak top moved around an amazing amount with seasonal variations in relative humidity, and the fabrication had to account for those changes. Abram's design was pretty good but his explanation was a bit thin on the how and why of the pegging aspect of the build.

                              The tongue on the OP's proposed table top is too short for a 7 1/2 inch wide breadboard end as Frank posted at #11. If it is glued and pegged, there is no material left to hold the pegs. Remember, the breadboard end is a cross-grain situation and the centre peg is the only one that can be drilled and glued into place. The outboard ones require a slot to accommodate expansion and contraction of the top. Don't rely on a dab of glue in the middle to keep the ends attached; it won't work! It would be wise to rework the tongues to be longer IMO and the grooves need to be deepened accordingly. If you are using 3/8" pegs (you should), the tongue needs to be about 4d long (so 1 1/2") with the pegs set at 1 1/2d from the edge of the breadboard. That will leave sufficient material to keep the ends supported and to keep the pegs from shearing out when someone inevitably levers themselves up using the breadboard end for support!

                              A breadboard end is not a mortice and tenon joint BTW but actually a pegged tongue in groove join. The pegs are essential for integrity of the join.

                              My 2 cents

                              Ken

                              PS the notation d (4d & 1 1/2d above) is the diameter of the peg; in my example and recommendation 3/8 inch. You could use 1/4" or 5/16" hardwood pegs as well ergo the terminology!
                              Last edited by KenL; 06-30-2020, 01:01 PM. Reason: I used some more obscure terminology and Doug pointed it out. I trust that the PS clarifies.

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