The object of the cap iron is to prevent a splitting action by bending the shaving forward, as shown in [Fig. 115]. At a is shown the effect when there is no cap, and at b the splinter bent over giving a shaving.
[XX]
SQUARING UP STOCK
Having prepared Harry for the serious work to come by his explanation of the plane and its operation, Ralph prepared to start his pupil on the most important and difficult problem in shopwork—squaring up stock.
"Anybody," he said "can hack away at a piece of wood with tools, and get some kind of result, but if this work is worth doing at all, it is worth doing well, and to be able to square up stock is perhaps the most important operation you will ever do. It is like mathematics, the answer is either right or wrong. When you finish, the stock is either square or not square.
"To square up stock means to reduce it to three definite dimensions, length, breadth, and thickness, with all adjoining edges or surfaces at right angles. It sounds easy.
"Suppose we want a piece 12 inches × 2 inches × 7⁄8 inch. First, saw out your stock about 121⁄4 inches × 21⁄4 inches × 1 inch. This allows something each way for the tools to remove in the process—for sawdust and shavings. It is considerably more than necessary, but on the first trial you waste more than later, when you have become skilled in this work.
"Second. Dress down one of the flat faces with the jack plane; follow with the smoothing plane and test, with straight edge, with the grain, across it, and diagonally across corners. When this face is finished it constitutes the foundation of the process, and is called the 'working face.'
"Third. Make a pencil mark on the working face near one of the edges. This is called a witness mark, and it indicates that the edge it touches is to be the next face dressed.