The following is excerpted from “The Essential Woodworker,” by Robert Wearing. In our opinion, “The Essential Woodworker” is one of the best books on hand-tool usage written in the post-Charles Hayward era. Wearing was classically trained in England as a woodworker and embraced both power and hand tools in his shop and in his teaching. The book is filled with more than 500 hand-drawn illustrations by Wearing that explain every operation in a hand-tool shop. His illustrations are properly drafted, drawn in perspective and masterfully clear.
Wood is porous and, depending on the atmosphere, will absorb or give out moisture causing it to expand or contract (Fig 215). This cannot be prevented, and allowance must be made for this movement in the construction of the table top. The amount of movement in length is negligible.
If the top is screwed directly to the frame it will either split due to contraction or bow due to expansion. This is the most common cause of split table tops. The problem is overcome using shrinkage buttons to secure the top. The mortices for these were discussed on p. 76. Buttons on the long sides must have room to move in and out so their mortices need to be only slightly longer than the buttons. Buttons on the short sides or ends need room to move sideways in the mortices which must therefore be longer.
To make the shrinkage buttons there are two possible methods (Fig 215b). The traditional method is to use short grain offcuts. Produce to thickness and remove a rebate. Then saw off the button. Repeat the process as required.
Using the more common long grain offcuts is the second method. Produce to width and thickness, bevel or round corners, saw out a rebate and then saw off the button.
Having made the required number of buttons, lay the table top flat and cramp the frame onto it. Check that the overlap on all four sides is correct. Make an improvised depth gauge and carefully drill into the table top.
The thickness of the buttons should be such that, when withdrawn sharply from the mortice, they will snap down against the table top. In other words, the length X on the button must be very slightly less than the length Y on the rail in order to obtain the vice-like grip (Fig 219).
The method of fixing is shown in Fig 220.