How to Make a Pair of Trammels
The making of these trammels is a very nice workshop problem for a school, as it requires a very small amount of stock and a corresponding degree of skill, and at the same time adds a little something to the general shop equipment.
The brass is best procured in strips, which may be had in different widths, except the bar, which is ¹⁄₄ in. thick and not less than ³⁄₄ in. wide. The steel for the points may be the ordinary steel, or if the trammels are to be used on woodwork, very satisfactory points can be made of heavy nails.
Trammel Points Made of a Nail and a Brass Strip to Fit the Bar
Cut two pieces of brass, 4¹⁄₄ in. long, and straighten them with a wood or rawhide mallet on a surface plate. Draw center lines both ways through each piece and lay out the openings for the bar with a sharp scriber, and make a center-punch mark for the ¹⁄₈-in. hole that is to be drilled at the intersection of the center lines. Mark the lines where the piece is to be bent, and with a pair of dividers lay out the ends and shape them with a file.
The center hole and bar openings are next drilled, and the latter finished by filing. It is better to plane up a short piece of hard wood, ¹⁄₄ by ¹³⁄₁₆ in., and use it as a gauge in filing the rectangular openings than to try to make them by measurement. Polish the brass pieces with a piece of fine emery cloth or paper, rubbing it in straight lines lengthwise of the stock.
The bending is done by clamping the pieces in a vise and bending first one side and then the other on the lines indicated. This will require some care, as the upper ends should be 1¹⁄₄ in. apart on the inside when the bending is complete. To insure the same angle on both sides, a template of wood is used, and the pieces are carefully bent to fit it.
The holes for the points are reamed tapering from the inside, where they are riveted in place. The points are filed to shape and polished, which is best accomplished in a lathe. Clamp one of the points in an upright position in a vise with the shouldered end up. Slip one of the brass pieces in place and rivet by upsetting the projecting end with a light hammer.—Contributed by J. A. Shelly, Brooklyn, N. Y.