Friday, November 30, 2007
Here is a photo of a bread board end on a cherry table. It is a table made by Timothy Clark, furniture maker. Notice the grain directions on the two boards are at 90 degrees to one another. Notice also the end board is proud of the top itself. What? He can't make them flush? Yes, he, and we can. But wood moves; it expands and contracts across the grain with changes in humidity and temperature. (I have a table whose drawer fits too tight in the summer, but loosens up in the winter. I made the tolerances are too tight. It sticks.) Here, he made the breadboard end a little extra bit proud for looks. I expect it flushes out in the summer. Build it flush in the summer, and in the winter the top is wider than the ends. Who has asked yet, "Why are these pieces moving? Aren't they glued together? " Nope. They are not. Bad idea,if they were glued together the breadboard end would constrain the table top from its normal seasonal expansion and contraction. As a result, it would split, lengthwise. I've seen cracks almost 1/4" wide. There are tenons on the table fitted into mortises on the breadboard. Glue is used only in the center 8" or so of the joint. The outside joints are pinned with dowels. See the small holes up there? Also, the holes in the tenon we do not see are elliptical so the tenon can move about. And they are usually draw bored. The holes for the dowel pins are offset from each other so that tapping in the dowel aligns the holes, and pulls the joint tight.
Boards with grain at 90 degrees to each other is called a cross grain situation. When 30" & 40" diameter trees could be logged, (colonial times), tables could be made using a single board. However, in addition to expanding and contracting across the grain, boards of this size tended to cup and bow. Breadboard ends were used to control this cupping. ( I presume those with glued-on ends survived as kindling.) Even though the tables we now make no longer cup, as they are made to width from several smaller boards, breadboard ends are still used. They look nice. The little pegs look nice. I make mine from contrasting woods with square heads, and leave them slightly proud. On the sideboard of mine(below) the curved up edges are pinned breadboard ends.
Tabletops. This is another place to avoid a cross grain situation, attaching a tabletop to the apron and legs beneath it. They are never glued on. Now, you understand why. S-shaped clips can be bought commercially to attach tabletops. One end is fitted into shallow grooves cut into the aprons, 1/8" high, 1/2" wide, 3/4" inches deep. Fit the clip into the groove and screw it to the underside of the table top. The top is held down, but can still move with the weather. I attach mine with wooden 'buttons' made from scraps of tropical hardwood. (I just don't have photos of everything!) I have also seen tables from the old days attached using screws. The screws fit into little pockets made on the table aprons using a brace and bit, and chisels. (The tables I've seen this on were made in the 1880's.)
Frame & Panel. Referring again to the sideboard below, look at the doors. This sort of door is called a frame and panel. The frame is made of stiles, the vertical board, and rails, the horizontal boards. Rails and stiles fit together with mortise and tenon joints. Around the inside perimeter of the rails and stiles a groove has been cut. The panel is let into the groove. Frame and panel doors solve two problems at once. They avoid cross-grain situations, and cover lots of area without having to use all solid boards. I use frame and panel construction on the backs of all my cabinets. (Instead of 1/4" plywood.) One can vary the widths and thickness of the frame members, beads can be cut in the stiles, etc. The left hand panel below, as an etc.,is not made of a single board, but five glued up to get the pattern I wanted. (In person you can't tell either.) Frame and panel construction is beautiful.
Posted by Kerry at 2:35 PM