Sunday, November 9, 2014

Collaborating on an Arts and Crafts Coffee Table - Gluing Up the Top with Breadbord Ends

Arranging and finishing a quarter-sawn white oak top offers a set of unique challenges.  Unless you have a large inventory of stock to draw from, you will likely be flipping and switching the boards around in a way to take advantage of the signature ray fleck pattern.  Once it works for you visually, chances are that the grain will be running in both directions along the top.   This table was no exception.

What this means, of course, is that you won't be pulling out a plane to level the individual boards or create a final finish -- it will be scraped and sanded into submission.  This is not too onerous if you take special care during the glue up.

The objective is to have the boards so straight and square that they practically guarantee a positive result.  Dimensioning the stock over several days helps tame the natural wood movement and a full scale dry-run predicts the outcome.  I happen to prefer pipe clamps, but Rob Porcaro over at Heartwood makes a compelling case for Jet bar clamps. 

I spring the joints on this 2'x4' glue up and use only enough pressure to get a uniform bit of squeeze out from the two middle clamps.  If I am wrestling and wrenching it, something has gone wrong in the preparation and this should have shown itself during the rehearsal.  The outer clamps need very little pressure.  If all goes well the greatest variation across the top will be less than 1mm.
After drying overnight, it took less than an hour to scrape and sand the top flat to 180 grit.  Still over sized, it was time to create and install the breadboard ends.

This top is +/- 1" thick so the tongue and groove will be cut at 3/8".  This is driven as much by my tooling (I have a 3/8" spiral router bit and a 3/8" pig sticker mortise chisel) as by convention.  I cut the blind groove first, dropping it down on the router bit in a series of passes (I hate this move) until I get the desired 5/8" depth.  After marking, I mortise the breadboard "tails" by hand.

I used my usual approach to using a router to cut the breadboard tenons and cut them to within 1/16" by machine.  A series of handsaws cut the profiles and rabbet and shoulder planes fine tune the thickness of the tail.

The extended length or "horns" on the end help while you are test fitting, and my goal is to have it just snug enough to slide into place with a few well-placed blows with the side of my fist.

The last step is to plane the final thickness of the ends.  This is a judgement call, but I like to have them just proud of the top, ensuring that all end grain is covered, but not so high as they might get caught and chipped during normal use.  I slide the end out about 1/2" and protect the top with masking tape.  From this point it is just a matter of test fitting until you are happy.

I secure it in my normal way (coincidentally, Jeff Branch just did a SketchUp version of breadboard ends which is a nice demonstration of this process) and take a look at how the proportions are working out.

Next up, we work on the legs and base construction.