Fig. 2376.
In [Fig. 2376], for example, the brass is shown in section in the strap, and the side a of the brass has a bearing against the jaw b of the strap, and hence would show marks of contact. The succeeding blows in driving the brass, however, may cause the brass to have contact on the side c with the jaw d; hence the bearing marks would show the brass to fit well when such was not the case. This may be detected by striking the brass on its joint face, and then measuring from e and from f to the end of the strap, and then striking the joint face at f and again measuring both distances, when any canting of the brass will readily be detected. It is better, however, to also apply the square, as shown in [Figs. 2374] and [2375], because by this means the joint faces e f being parallel to the crown face g of the brass, the brass will be fitted so that when g meets the crown face h of the strap, the two will be parallel to each other and require but little filing to fit or bed together.
The crown of the brass should be bedded very finely to the strap, or it will spring the strap jaws away from the rod when the key is driven home.
Fig. 2377.
Suppose, for example, that the crown of the brass did not bed well at a in [Fig. 2377], then keying up the strap would spring its jaws away from the rod end, as shown at b c, the least error in the bedding having this effect notwithstanding the fit of the gib jaws.
The second brass must be made to just fit the strap when the back brass is in its place, and is small enough when the calipers, set as shown in [Fig. 2373], and tried as shown in [Fig. 2376], just fit the strap. This will insure that both brasses fit the strap when it is in its place on the rod.