The gage consists of a stepped block _B_, mounted so as to slide upon the inclined edge of the block _C_. There are V-ways upon the upper edge of the latter, and the block _B_ is split and arranged to clamp over the ways by the screw shown at _S_. All parts of the gage are hardened and the faces of the steps marked _A_, are ground and finished so that at any position of the slide they are parallel to the base of the block _C_. The lower split portion of the block is spring-tempered to prevent breaking under the action of the screw, and also to cause it to spring open when loosened. The gage has the advantage that it can be quickly adjusted to any size within its limits, which does away with using blocks. In planing a piece to a given thickness, the gage may be set to that height with great accuracy by means of a micrometer caliper, and then the planer or shaper tool adjusted down to the gage. This method does away with the "cut-and-try" process, and will bring the finishing cut within 0.001 inch of the required size. If the piece being planed, or the opening to be measured, is larger than the extreme limit of the gage, parallels may be used. In fitting bushings into bushing holes, the adjustable gage may be moved out to fit the hole, and then, when the bushing is finished to the diameter given by the gage, as determined by a micrometer caliper, a driving fit is ensured.[26] Radius Gage [Illustration: Fig. 49. Radius Gage] Fig. 49 shows a radius gage which has proved to be very handy for all such work as rounding corners or grinding tools to a given radius. The blades are of thin steel, and are fastened together at the end by a rivet, thus forming a tool similar to the familiar screw pitch gage. The right-hand corner of each blade is rounded off to the given radius, while the left-hand corner is cut away to the same radius, thus providing an instrument to be used for either convex or concave surfaces. The radius to which each blade is shaped is plainly stamped upon the side.[27] Gage for Grinding Drills [Illustration: Fig. 50. Gage for Grinding Drills] Fig. 50 shows a gage for use in grinding drills, which has been found very handy and accurate. This gage enables either a large or small drill to lie solidly in the groove provided for it on top of the gage, and the lips can then be tested for their truth in width, or angle, much easier and quicker than with the gages in common use without the groove. There is a line, to set the blade _B_ by, on the stock at an angle of 59 degrees at the top of the graduated blade, and the user can easily make other lines, if needed for special work. The blade is clamped in position by the knurled nut _N_ at the back, and can be thus adjusted to any angle. The stock _A_ is cut away where the blade is pivoted on, so that one side of the blade comes directly in line with the middle of the groove.[28] Tool for Gaging Taper Threaded Holes [Illustration: Fig. 51. Tool for Gaging Taper Threaded Holes]