The plumb-bob method is so familiar and, where not familiar, so easily thought out in its various applications, that we deem it useless to touch upon it.

The stringers or supporting timbers of drop hangers should be equal in thickness to about one-fifth of the hanger drop.

Where the stringers run with the hangers and crosswise of the shaft, both feet of a hanger base are bolted to the same stringer, and this should be from 1¼ to 1½ times the width of the widest portion of the hanger base. As the hanger is securely bolted to its stringer, this extra width is in effect an enlargement of the hanger base, and thus enables it the better to assist the shaft's end motion.

Where the stringers run with the shaft and crosswise of the hangers, the two feet of the hanger base are each fastened to a separate timber, and these should be equal in width to the length of one hanger foot, plus twice the amount of adjustment (if there be any) the hanger's supporting bolt slots will allow it. In reckoning hanger adjustment, be sure to figure in the bolt's diameter and to bear in mind that to get the utmost adjustment for the countershaft the bolts should originally be centered in the slot; thus a 13/16 × 1½-inch slot, as it calls for a ¾-inch bolt, leaves a ¾-inch play, and this play, with the bolt in the center of the slot, allows of 3/8-inch adjustment either way. Without this extra width addition any lateral adjustment of the hanger would result in leaving a part of the hanger's feet without stringer support. Such jobs look poorly, and often run still more poorly. Fig. 36, in its two views, will make the above points clear.

Fig. 36.

In the stringing of countershafts whose hangers have no adjustment it often happens, despite all care in the laying out, that they come 1/8 to ¼ inch out of parallel. A very common and likewise very dangerous practice at such times is to substitute a smaller diameter supporting bolt instead of the larger size for which the hanger foot is cored or drilled, and to make use of the play so gained for adjustment.

That shafting so carried does not come down oftener than it does is due solely to the foresight of the hanger manufacturers. They, in figuring the supporting bolt's diameter as against the strain and load to be sustained, are careful to provide an ample safety margin for overload, thus enabling the bolt substituted to just barely come within the safety limit under easy working conditions.

The largest-sized bolt that a hanger will easily admit should invariably be used, and for alinement purposes either of the following slower but safer methods should be used.

Rebore the hanger-supporting bolt holes in the stringers to a larger size, and use the play so gained for adjustment. It is not advisable, however, to rebore these holes any larger than to one and three-quarter times the diameter of the bolt to be used; and the diameter of the washers to be used on top of the stringers should be diametrically equal to at least twice the size of the rebored holes. That the washers used, under such conditions, must be of a good proportionate thickness goes without saying.