In the case of very large rods the two ends are made and fitted up as separate pieces, and are afterwards welded to the body or stem of the rod, and the setting of the ends true one to the other after the welding affords such an excellent insight into the alignment of rods that it may be well to describe it. First, then, the rod being laid on its side, two straight-edges, or rather winding strips, s and s′, [Fig. 2361], are placed on the side faces, and the rod will be set in this direction when their ends a, b, c, d, appear parallel when sighted by the eye. If the winding strips are adjusted to stand straight across the rod, and, therefore, parallel one to the other, any twist or wind in the two rod faces will be very plainly discernible by the sighting process. The rod is then stood on edge, as in [Fig. 2362], to test the alignment of the side faces. A straight-edge s is pressed firmly against one of the faces, as h in the figure, with the other end elevated as shown. The elevated end is then lowered, the motion serving to keep the end fairly bedded against face h. The distance, i j, [Fig. 2363], is then measured. The straight-edge is then used in the same manner on the other side of the rod as at s in the figure, and the distance k l is measured, the setting in this direction being correct when distances i j and j k are equal. The straight-edge is then applied to the edge faces of end h of the rod, as in [Fig. 2364], at m and at n, the distances o, p, are made equal. During these operations a straight-edge is applied along the body of the rod to see where to set it to effect any required adjustment, and if that body is straight the adjustment is made near the end at which the straight-edge is pressed to the rod.
Fig. 2365.
The setting of the small end i is effected in the same manner, but the straight-edge will in this case fall over the face at the larger end, as is shown in [Fig. 2365]; hence, instead of measuring, lines as g and t are marked coincident with the edge of the straight-edge and the distances t u, i g, are made equal. Winding strips are applied to the edge faces as well as to the side faces, and as making one adjustment or alignment may alter another, the whole process must be repeated until the whole of the tests prove the setting to be true.
Fig. 2366.
