The try square should be about six inches long at the blade or measuring side, and should be entirely constructed of metal and the measuring blade should be marked off in inches and fractions thereof. Good try squares may frequently be purchased in the 5 and 10 cent stores and these are quite accurate enough for the purpose. The spring dividers should be about 6 inches in length. These dividers are held open by the strong spring in the top and are opened and closed by a nut acting on the screw thread. Do not purchase the heavy dividers or compass commonly used by carpenters as these are not as capable of the small adjustments as are the spring dividers. The spring dividers may sometimes be found at the 5 and 10 cent stores and may always be found at good hardware stores and tool houses.
All the tools used for laying out and marking off the work are plainly shown ([Plate VI]).
Laying Out Work.—It should be borne in mind that a little time spent in carefully measuring, laying out and marking off the work will make a great difference in the finished appearance of that work, so that these simple operations should not be slighted.
The steel square should always be used in laying out rectangular work: lines that are supposed to be at right angles or “square.” Work that is not carefully laid out or square will not fit together neatly if it fits at all.
One of the first things that one has to do in the tin can work is to trim up a piece of tin that is taken from the side of a can and flattened out.
Suppose that such a piece of tin has been cut from a can and flattened out, the edges of such a piece of tin are rather jagged and the whole piece should be trimmed off square before trying to use the tin for various purposes.
First place the ruler as near to the upper edge of the tin as possible and so as not to include any of the jagged cuts. Hold the ruler down firmly and draw the point of the marking awl along the edge of the ruler until a straight line is scratched along the edge of the tin. The surplus tin above this line should be cut away with the metal shears by cutting along from right to left so that the narrow and jagged strip of tin is curled up out of the way by the shears as it is cut. When the surplus tin is cut away you should have a straight clean edge at which to begin the marking operations.
Using the Try Square.—Next, the two ends of the piece of tin should be squared off using the try square for squaring up the ends as follows: Place the heavy solid part of the square firmly against the freshly cut straight edge of the tin, near one end in such a manner that the blade of the square with the inch divisions marked on it lays squarely across the tin, and as near as possible to the end of the piece but not including any of the jagged cuts. The position of the square is shown in [Fig. 1].
Fig. 1.