Abstract: Apparatus for setting cutting tool length on numerically controlled machine tools includes a base having a leg extending perpendicularly therefrom. A rod is fastened to the base parallel to the leg. Overlying the end of the rod distal from the base is a cap which is reciprocal along the axis of the rod and which is biased away from the base by a spring interposed between the rod and the cap. A dial indicator gauge is fastened to the rod to abut the cap for indicating the displacement of the cap along the rod relative to the base. A setting block is pivotally mounted to the leg a known distance from the base and is rotatable about the axis of the leg for urging the cap against the spring so that the distance between the cap and the base corresponds to the known distance between the setting block and the base, to facilitate zeroing of the dial indicator gauge.