Monday, July 7, 2014

A Square Deal (12)

I last left off with the table top slab tenoning work complete:


Now it is time to cut out and fit the breadboard ends. These are made from quartersawn bubinga, which have been jointed and planed over a couple of rounds to obtain straight and square-edged stock.

The breadboards ends are triple-mortised, with a stepped dado and rebated on both sides. The simple dado was cut first, and this groove jigged the cut out of the mortises, which I did on the hollow chisel mortiser:


After the mortise floors were cleaned out, I processed the step in the mid portion of the dado, and then rebated the side arrises:


Another view:


First time fitting:


It was the desired fit, requiring only gentle strikes with a dead-blow mallet to fit the piece up:



Together:


The other side also went on without a hitch:


The breadboard ends are left long for the time being, the 'horns' being a useful means of tapping the ends off when required.

Next I'll move the coffee table top along through the same steps to fit breadboard ends. When I'm done I'll update this thread with another posting.

Thanks for coming by the Carpentry Way. On to post 13.

8 comments:

  1. Interesting joint between the breadboard and the top. Looks good!

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  2. What is the amount of dimension change you anticipate when the top shrinks or swells?.......Jack

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    1. Jack,

      good to hear from you. Given the material, the grain composition of the top, and the seasonal relative humidity variation in the installed location, I have calculated the annual movement to be 1/4". The joinery is designed to accommodate that. My experience with bubinga from past pieces and some familiarity with the install location leads me to believe that 1/4" movement will be worst case scenario.

      Since I've had the panel in my shop - several months now - the top hasn't changed appreciably in width. It's maybe 1/16" fatter, at most, than when I brought it in, and the ambient humidity has climbed a fair bit in recent weeks, as I'm sure you know given where you live. I'll continue to observe the panel, checking it every day, and if I get any inkling that movement will be greater than anticipated, I'll adjust joinery detailing accordingly.

      ~C

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    2. I think I understand now. There are no frame parts at the table tops edges. You will see the dimension change as being either protruding beyond the frame ends, or short of the rail end. Less or more of the hammerhead shows as change happens.

      Did you decide on this tactic to avoid the gap that would show between the side frames and panel? Would you use side frames if you could hide dimension change otherwise?........Jack

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    3. Jack,

      if you look back to earlier posts in the series you will see design renderings. Yes, the top projects out from the supporting members all around. Yes, given shrinkage and swelling of the top, less or more of the hammerhead will show, along with some discrepancy between the end of the breadboard and the side edge. The hammerhead serves two functions, one is to lock the end of the breadboard end in place and the other is to help mask the dimensional differences between parts that will manifest through the year of humidity changes.

      I chose this tactic as it seemed the optimal solution given the desire to use a slab top for the table. The top will move, no matter what. It's solid wood, that's what it does. The breadboard ends stiffen the top somewhat, and cover over all the end grain, which helps dampen moisture exchange. The relief grooves on the bottom weaken the top's ability to cup, promoting stabilty. All the movement in the top's width will manifest at the juncture between the ends of the breadboards and the table edges. I saw the Greene and Greene solution to the same problem, that of a decorative spline with largely fake pegging as a kernel of a good idea. Things evolved from there.

      If the top had not behaved itself, my solution would have been the classic Chinese one of a frame and panel top, with the panel stiffened with dovetailed battens. Still, it is so much nicer to have a table top without the muck-catching grooves you have to have in a frame and panel, both aesthetically and practically.

      You might want to take a look at my 'Ming inspiration' series for another approach to a frame and panel top, where the top is made to look as if it is a slab. That's proven to work well, and I got the idea from a unique 16th century Chinese table.

      ~C

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  3. Chris,

    I've just spent the last 2 days reading all 12 entries in this build. I have to say that your level of knowledge and quality of work is astonishing. As a weekend warrior i could only dream of building something of this caliber. I find it amazing that there are still people out there that understand the value of a fine hand made heirloom piece of furniture. Something that will easily out live it's owner. I have made pieces that will definitely go to my children but this is a piece that will be handed down for generation to come. I can't wait to follow along with your process on this project, i'm a little disappointed that i'm caught up, i may have to start reading on another of your projects. Keep up the great work and never back down on the length of your entries. I feel like learn something every time i read one of them.

    John Gray

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  4. John,

    many thanks for your comment and I appreciate the encouragement. My client is the one making the project possible, and he has been great to work with so far.

    ~C

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