Springy tools are provided with arched ends named springs, and each spring has a cutting end which is in a particular shape to suit its intended work. These instruments are represented by Figs. 450, 451, 452, 453, and 454. The spring of a tool for roughing is much thicker than that of one for smoothing, a greater resistance being necessary for making a thick shaving than for a thin one. A narrow tool for roughing is shown by Fig. 450, and a broader one for smoothing is indicated by Fig. 451 ; this tool has a nearly straight cutting edge, that a broad surface may be presented to the work at the time of cutting. - A right-hand springy tool for shaping curved inner corners is shown by Fig. 452, and a left-hand tool for similar corners is seen in Fig. 453. A tool for convex or outer corners contains a gap, and the curve of the gap is rather greater than the curve of the corner required to be made with the tool. A tool which will shape both inner corners and outer ones is indicated by Fig. 454.