valves move with them. The valves and buckles are placed in position inside the steam chests, the back ends of the spindles being cottered to the valve rods, which work in circular guides forming part of the motion plate. The accuracy of the work must be such that the centre lines of spindles and guides must either coincide exactly or if, as is frequently the case, there is an offset the centre lines must be perfectly parallel to each other. The spindles must move freely without shake or binding in the guides.
Whilst the above work is being done to the motion, other erectors may be fitting the axleboxes into the hornblocks by filing the side faces until they bear evenly on the horncheeks. The boxes should be a fairly tight fit between the hornblock faces, but not so tight that they cannot move up and down to allow for the vertical movements of the springs. Everything must be perfectly “square,” and the axleboxes on one side exactly in line with those on the other, otherwise the axles would be on the “skew,” and the locomotive would run badly. The hornblock faces on opposite sides of the engine have previously been finished exactly in line and tested across the engine by straightedges, and the machining and boring of the axleboxes is done so accurately by modern methods that the centre of each axlebox is equidistant from each of the hornblock faces.
If the work has not already been done in the wheel shop, the axleboxes, after having been removed from the hornblocks, are fitted to the
