Setting Line Shafting in Line.—The following method of adjusting line shafting or setting it in line, as it is termed, is that generally adopted in the best practice.
Fig. 2585.
Fig. 2586.
First prepare a number of rude wooden frames, such as shown in [Fig. 2585]. They are called targets, and are pieces of wood nailed together, with the outer edge face a planed true, and having a line marked parallel with the planed edge and about three-quarters of an inch inside of it. Upon this frame we hang a line suspending a weight and forming a plumb-line, and it follows that when the target is so held that the plumb-line falls exactly over and even all the way down with the scribed line, the planed face a, [Fig. 2586], will stand vertical. To facilitate this adjustment, we cut a small V notch at the top of the scribed line, the bottom of the V falling exactly even with the scribed line, so that it will guide the top of the plumb-line even with the scribed line at the top; hence the eye need only be directed to causing the two lines to coincide at the bottom. To insure accuracy, the planed edge a should not be less than a foot in length. Then tightly stretch a strong closely-twisted and fine line of cord beside the line of shafting, as shown in [Fig. 2587], placing it say six inches below and four inches on one side of the line of shafting, and equidistant at each end from the axial line of the same, adjusting it at the same time as nearly horizontally level as the eye will direct when standing on the floor at some little distance off and sighting it with the line shaft.
