The combination caliper and divider shown in Fig. 15 is one that is not manufactured by any of the various tool companies. It is, however, one of the handiest tools that can be in a machinist's kit, as it lends itself to so many varied uses, and often is capable of being used where only a special tool can be employed. The illustration suggests its usefulness. The tool can be used as an outside caliper, as an inside caliper, and as a divider. The common form of this tool has generally only one toe on the caliper legs, but the double toes save the reversal of the points when changing from outside to inside work. The divider points may be set at an angle, which permits of stepping off readily around the outside of a shaft at angular distances, where the ordinary dividers are useless. A number of other uses could be mentioned, but any intelligent mechanic can readily suggest them for himself. [Illustration: Fig. 15. Combination Caliper and Divider] Attachment for Vernier Calipers While vernier and slide calipers are very handy shop tools, their usefulness is much more limited than it ought to be for such expensive instruments. In order to increase the usefulness of these tools, the attachments shown in Fig. 16 may be made. In the upper left-hand part of the engraving the details of a useful addition to the caliper are shown. _A_ is made of machine steel, while the tongue _B_ is of tool steel, hardened and ground and lapped to a thickness of 0.150 inch, the top and bottom being absolutely parallel. This tongue is secured to _A_ by the two rivets _CC_. The thumb-screw _D_ is used for fastening the attachment to the sliding jaw of the vernier or slide caliper. In the upper part of the engraving is shown the base, which is of machine steel, with the slot _F_ milled for the reception of the fixed jaw of the caliper. The set-screws _GGG_ are put in at a slight angle so that the caliper will be held firmly and squarely in this base. In the figure to the left these pieces are shown in the position for forming a height gage, for which purpose the attachment is most commonly used. As a test of the accuracy of its construction when the attachment is placed in this position, the tongue _B_ should make a perfect joint with the fixed jaw of the caliper, and the vernier should give a reading of exactly 0.150. When it is desirable that the tongue _B_ should overhang, the base _E_ is pushed back even with the stationary jaw, as shown in the engraving to the right. In this position it is used for laying out and testing bushings in jigs, etc. The illustration shows the tool in use for this purpose, _K_ being the jig to be tested. All measurements are from the center line upon which the bushing No. 1 is placed. Taking this as a starting point we find the caliper to read 1 inch. Bushing No. 2, which is undergoing the test, should be 5/8 inch from this center line. It has a ¼-inch hole, and we therefore insert a plug of this diameter.