Fig. 38 shows the connecting rod for a small steam engine. This piece calls for little comment. The outlines of the crank pin and cross-head pin are shown in dot-and-dash circles, and the relation of these centers to the rod is given. This is of some importance in enabling the detail of the boxes, which go in the heads of the connecting rod, to be correctly detailed and checked. It should be carefully noted by the student, that any such information which can be given on the details, without confusing the drawing, to tie up one detail with another, is usually good practice. It not only saves time in the drafting room in checking and general reference work, but it gives the workman a better idea of how the parts are expected to go together, thus fulfilling the general definition of a working drawing as "complete and definite instruction".

Fig. 38. Detail of a Connecting Rod.