Breadboard tabletop

[Andy B]

Hi everyone,

I am new to the forum but have had a kreg jig for a couple of years now.

I am currently building a coffee table for someone else and need it to be spot on. I want to construct the top with breadboard ends and was going to kreg them together (not sure if I can use the name as a verb) by I am worried about expansion. Does anyone have any information, advice or experience that could help with this?

Cheers,

Andy

[Russ Haynes]

Good idea to consider expansion. Can you provide the dimensions and type of lumber? How wide it is and the type of lumber will provide more information that would enable us to figure out how much expansion you are likely to get. Also, what climate will the table reside in? I typically only fasten the breadboards to the center boards and then allow for more expansion the closer you get to the edges. I usually dowel and glue the center. Pocket holes are fine as you get closer to the edges, but I enlarge the holes depending on how much movement is expected. To do that, you should drill the pockets in the breadboards and screw into the table top. You can make the pockets larger and dril out the pilot part of the holes with a larger bit no wiggle it around until you allow for the proper amount of expansion.

[Andy B]

Thank you for your reply. The wood is 28mm by 134mm. I was hoping to kreg the top together and the top to the apron but I am worried about movement so unsure how to proceed.

In terms of climate I am in the UK

[Russ Haynes]

Thanks, that tells me how wide the boards are.  How thick are they and what kind of wood is it?

[Andy B]

They are 28mm thick redwood

[Russ Haynes]

Got it (for us neanderthals, pretty close to 1-1/8" thick by 5-1/4" wide).  Assuming this is young-growth redwood and that your relative humidity swings from approximately 25% to 90%, winter to summer, then you can expect each board to expand approximately 0.5 to 1.0 mm.  So if your table top consists of 6 boards, you could get between 3 and 6 mm of expansion.  If you screw the breadboard to the two center boards, then on the next two boards, you should elongate your hole by 1 mm.  On the next set, by 2 mm, etc. to allow for expansion.  That should prevent your breadboards from blowing up your table top.  If you're worried about strength due to the oversize holes, you can add (unglued) dowels in elongated holes to provide more vertical strength to the breadboards.  Hope this helps.

[Andy B]

Very helpful, thank you very much


Am I to assume a similar set up for attaching the top to an apron?

[Russ Haynes]

Yes, the top is going to expand and contract along the breadth of the boards.  That will occur at the ends (where the breadboards are located) AND at the center.  The best way to address this when securing the top to your aprons is to use buttons to attach the top to the aprons.  Here is a link to an article that discusses the use of buttons and instructions on how to make and install them yourself.  You can also select from a wide variety of table top fasteners that will secure the top to the aprons but allow for expansion and contraction, e.g. "figure 8 fasteners."