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 1/4 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.
When the reboring method cannot be used--as when the hangers are carried by lag screws, lag-bolts, bolts screwed directly into supporting iron girders, etc.--it is evident that hanger adjustment can be secured by packing down one foot of the hanger base, as shown in Fig. 37.
The piece of packing (necessarily wedge-shaped) between the hanger foot _B_ and the stringer _A_ tilts the bottom of the hanger forward. The size of the wedge regulates the amount of adjustment. Wedge-shaped space _D_, at foot _C_, should also be packed out so as to avoid throwing undue strain upon _C_'s extremity _c_. If now, the foot _c_ of the countershaft's other supporting hanger (No. 2) be similarly and equally packed, as _B_ of No. 1 hanger, the shaft will have been thrown forward at one end and back at the other, and thus into line. The equal division of the adjusting wedge packing between the opposite feet of the two hangers enables a limited packing to do considerable adjusting without any undue marring effect; and, further, insures the shaft's remaining level, which evidently would not be the case if only one hanger were packed down.