Sliding Dovetails

Sliding dovetails are a traditional and painstaking endeavor and are necessary to properly attach a large panel, like a table top, to a frame. Not many furniture builders would bother using them though as that screws and brackets are a lot faster and work just as well - for a while.


In response to humidity changes boards shrink and swell to different extents depending on which axis of the board you measure (see living material / education tab). The greatest axis for dimensional change is in the width of a board, while the least is in the length of a board. So in a table you have several boards' edge glued to make a top, and a longitudinal stringer running perpendicular under them. This aligns the maximum shrink/swell axis (across boards of the table top) with the minimum shrink/swell axis (longitudinal axis of table stringers) causing stress and strain as the woods cycle differently. This is a particular problem with tables because of the large size of their top panels. A standard sized dining table can easily swell in width by a 1/4´´ or more seasonally, while the stringer it is attached to wont grow in length much at all. If there isn't some mechanism to allow the boards to move independent of each other then eventually something will split or crack.


The sliding dovetail joint takes this difference in swelling into account by allowing the table top to shrink and swell as necessary while still holding the top firmly onto the frame. In principal the sliding dovetail acts like a sort of reverse keystone or wedge, the freely sliding dove part resides snugly in the table panel while the tenon part is glued into a mortise in the frame. The dove portion of the joint is in fact waxed, not glued to reduce friction and allow free motion of the top.