Wednesday, November 7, 2012

Bread Board End Experiment

Things Get Messy & Cluttered
     Seems like most woodworkers I know tell me they'd like to have a bit more shop space and I agree whole heartedly.  Although that would probably mean I'd have a bigger mess to clean up but at times it sure would be nice to have more horizontal surface to put stuff on!  That's my bench after a couple hours of working out the ends for the table I'm planning to build.  It will be a sofa table and made of Sapele.  I'm wanting to incorporate some carving into it so have also been experimenting with that as well.  It's not quite ready for human consumption but I'll share it when it is.  The design is based on the Star Jasmine flower.  We have one in the back yard and it puts out a very small, spiraled flower that is serving as my inspiration for the design.  Almost ready to show the carving idea so be patient!
     The table will be about 16" wide and just short of 6' in length.  My plan is to have the sides ever so slightly curved for some visual interest.  It'll be a very elongated oval.  The Sapele I have is 4/4 so to add some weight to it I will laminate a 5/16" thick piece to the edges so I can have a top of about 1 1/4" thick.  Here's the experimental piece; glued, clamped, and ready to go.

Clamped Up

     The next step is to plane a taper on the sides to add that visual interest I want.  Arbitrarily I decided to come down from the top an inch and also in an inch from the side.  Now that you see this let me explain the reason for  making an experimental piece first.  The purpose of a bread board end is to conceal the end grain of the wood and also helps keep the table top flat.  I don't want to laminate a length of end grain wood all the way across the 16" width of the table, only the edges like in this picture.  I need to see how this will all work so the experimental piece is a good way to go about that.

Bottom Taper Laid Out (Also the Tenon)

     After laying them out the next step was to plane them to the line and level the entire length of the piece.  Easy enough on an 8" section, the 6' or so table will be a little more challenging!

Taper Planed and Checked
          A piece of 1 1/4" thick will be used for the breadboard end.  Lay out is done with the marking gauge after the groove was cut with a hollow chisel mortiser.  Sure, could have done it entirely by hand but since I have the machine I'll always let it do the "grunt work".

Lay Out Complete 
     Usually, the groove would be pretty much centered in the breadboard end but not in this instance.  The pieces laminated to the edge of the top will give the illusion of a thicker top so I'll need to mimic that at the ends.  The tongue for a breadboard should be about 1/3 the thickness of the top, that's about 3/8" for a 1 1/4" top.  I used the combination of a tablesaw to rough out the tenon then a rabbet block plane to bring it to size.

Breadboard Tongue Complete

     Keep in mind that this is a very short, experimental piece.  In practice the tongue would not be full width the entire length.  Usually only the center 2" or so and the same space at the ends will be 3/4".  The remainder could be half of that.  The purpose of this joint is to allow the boards that make up the table top free movement with humidity changes.  It is pinned or screwed and only glued at the center.  This way the boards can expand and contract without splitting apart.
     I made a 5/16" dowel out of a piece of Maple and located it in the center of the board.  Here I'm setting up the drill press so the dowel will go into the bottom of the breadboard end but not completely through.

Adjusting Depth for Dowel

     I think it's wise to clamp the breadboard end so that it is tight up against the shoulder of the table top when you drill it.  Pretty easy on this experimental piece but when you do an actual table top it calls for some creative clamping.  An alternative is to use a hand held drill.

Drilling Dowel Hole

     Before assembly, the dowel hole needs to be elongated in the tongue to allow for that movement I mentioned earlier.  A round file works best for that.

Elongating the Hole

     To assemble this joint you only apply a small amount of glue to the center of the tongue.  With an actual table top you would also have a dowel at both ends.  Glue is applied to the dowel but not too much.  It is important though to have glue in the bottom hole so the dowel is secure.  It's not unheard of to put a coat of wax on the tongue itself just to be sure no glue holds it to the top and prevents that movement.  Honestly though, here in the desert seasonal changes are not a huge concern -- things are pretty dry all of the time.  It's still important to plan for it in your design process.  The dining table I made of Canarywood has seasonal movement.  I can tell because the ends of the table and breadboard are only flush about half of the year, the other half the boards shrink across the width and they are no longer flush.
     At this point, things are clamped together and we're waiting till morning to see how they look.  Again, clamp the pieces together to get the breadboard end tight to the table top.  I'm anxious to see how the planing will go as I  match the edge profile to the breadboard end.  I also want to finish this piece to see if the Maple dowel will compliment the Sapele.  I'll probably peg the tenons on the apron to continue that design element.  Let you know tomorrow how things work out!



  1. Since there is one peg, why do you enlarge the hole to allow movement?

  2. Looks like you're having fun with your experiment, but from what you have shown you would appear to misunderstand the logic of pegging the breadboard end.

    More specifically:

    1) It doesn't make sense to enlarge the middle peg hole when there is a single tenon. The tenon can be pegged normally in the middle, and simply create room at both ends of the mortise and all will be fine. When multiple tenons are used, one tenon can be pegged normally (usually at the middle tenon or at an end tenon) and the rest of the tenons made with elongated slots. The holds the breadboard end in a fixed position relative to the table top and allows for seasonal movement.

    2) It is unnecessary to glue the peg if you employ a modest amount of draw bore, which could have been done instead of your clamp and drill through method.

    3) Due to your pegging technique of clamping and drilling, if the breadboard end shrinks across its width to any significant degree at some point down the line, a gap may open up off the end grain of the tenoned board and the breadboard will be held off, hanging on the peg.

    4) Even with going ahead and gluing the peg as you have done, the usable glue surface is only about 50% of the connections peg mortise, at either tenon or breadboard end mortises, so it is a weak connection at best. This weakness is compounded in the above example by making the breadboard end's mortises blind. Further, you mentioned, "you only apply a small amount of glue to the center of the tongue", which has the elongated peg mortise, and that thereby has ZERO decent gluing surface.

    Excuse my bluntness, but the method you are describing above makes no sense structurally and I might suggest a rethink.

    1. No problem, appreciate your bluntness. The main experiment here was to see about forming the underside of the table with the taper. On the actual table there will definitely be a peg on the ends as well. Probably should have been clearer on that point. I only wanted to illustrate the elongation of the hole but normally only the end holes would be elongated with the center essentially glued tight. I like your suggestion of draw boring the center hole to eliminate the problem with the breadboard shrinking in its width. Usually I'll make the mortise longer than the tenon to allow for movement.
      Sound like a better plan to you? I really wanted to see how it would work to have the breadboard be 1 1/4" thick and the table top only laminated on the edges to give the illusion the entire top was that thick.

    2. I appreciate the dialog. I'd sound one note of caution in regards to draw-boring: as the design currently stands, the tenon is very short and has precious little relish beyond the peg hole, and if the draw bore is too pronounced, it will crack that relish off. Some combination of tenon and mortise lengthening (perhaps a through tenon instead of a blind one?), peg shrinking (to a 3/16" or 1/4" peg), and making the draw bore offset fairly minimal (about 1/32") would be wise moves.

      The draw boring, by the way, can be done to all the pegged tenons, even the elongated ones.

      An alternate strategy given a longer breadboard end than shown in your example would be to make the breadboard end slightly bowed along its length so that when fitted to the tenoned board it has an edge-to-edge gap at the middle tenon, and then peg it only at that middle tenon. That puts the connection - indeed the entire breadboard piece - under elastic tension, and the breadboard's ends are not going to open up away from the board.

      The 'thickened edges strategy' for making an otherwise thin table top panel look more like a slab has been done before. I've seen it on a 16th century Chinese table, albeit with a joined connection instead of a glued one. But the purpose was the same.

      Have fun!