Fig. 34 shows the detail of a rocker arm and pin, such as are frequently found in connection with the valve gear of a steam engine. This is a case where it is just as clear to detail two pieces together as to separate them entirely, the rocker arm pin being shown in position in the large hub and dimensioned in that position. This is not only simpler, but it gives the added information to the workman of just how the pin goes in the arm, and enables him to make his fits accordingly.
Fig. 34. Detail of Rocker Arm and Pin.
This principle of detailing several pieces together may, however, be carried to the point where the drawing becomes confused and complicated; then it is best to separate the detail of the parts. There are often special reasons requiring the detailing of parts of one kind on one sheet and of another kind on another sheet; for example, some shops detail forgings on one sheet, castings on another, parts to be made on the screw machine on another, and turret lathe work on another, etc. Such arrangements are, however, dependent upon the particular shop organization to which they apply.
Fig. 35. shows a link stud, also used in connection with the valve gear of an engine. On such pieces as this it is usually considered that they are finished all over unless otherwise mentioned. It is always desirable, in finished pieces of this character, to give the length over-all of the pieces, in order that the workman may quickly determine how much stock to order from the stock room without having to add up the figures between the various shoulders of the piece. The head of this stud is a hexagon, and the usual method of calling for the hexagon is given in the note, "2" across flats". The reason the distance across flats is specified is to enable the workman to see at once what the necessary width of the jaws of the wrench must be in order to fit the head of the stud.
Fig. 35. Detail Drawing of Link Stud.