Fig. 1465.
A better plan is shown in [Fig. 1465], in which a is the surface plate, b a cylindrical piece of iron turned true and parallel in the lathe and having its end face true and cupped as denoted by the dotted lines so as to insure that it shall stand steadily and true. The surface of a and the vertical outline of b forming a true right angle we have nothing to do but make the square s true to them when placed in the position shown.
Fig. 1466.
Fig. 1467.
