Fig. 68. Boys' designs for letter racks
The wood in the centre was removed with a 1⁄4-inch chisel, and the process continued until a uniform depth of 1⁄4 inch was reached. After all three grooves had been cut, the edges of the base were bevelled with the plane. This bevelling could have been done readily with the knife, but much time was saved by using the plane, always doing the long sides first.
In all the letter racks shown in the illustrations the construction was the same. First, the three blank partitions were made, then finished in their outlines with knife and sand-paper. The carving was always drawn carefully on the surface of the front piece. Third, came the making of the base, and last, the gluing of the partitions into the grooves. To increase the strength of a letter rack, 3⁄4-inch brads can be driven from the bottom into the partitions, but where this is done it is safer to draw pencil lines on the bottom directly under the centre of each partition. Place the point of the brad exactly on the line before hammering.
Fig. 69. Form "A"
Although the forms of the letter rack are endless, the one which our boys found most interesting was based on the ellipse. It called forth a very instructive drawing lesson. Ralph showed Harry first how the figure could be drawn by a string, with two pins to represent the foci of the ellipse. The figure has two dimensions called the major axis and minor axis. ([Fig. 70]).
Fig. 70.