_a._ Slide valves must be machine fitted on all four of the outer
edges, the exhaust port edges, and the surfaces in contact with rod
connections.
_b._ The slide valve itself must have its steam and exhaust edges
fitted up “line and line” with their respective steam and exhaust ports.
The adding of lap to these edges in lieu of lost motion is not
acceptable further than a possible 1/32 of an inch to cover
inaccuracies of edges.
_c._ The valves must be guided laterally by guide strips cast in steam
chest, and these strips must be machine fitted. The lateral play at
these surfaces should not exceed 1/16 inch. The height of these guide
strips should not be less than 1/2 inch, measuring from valve seat.
The construction must be such as to absolutely preclude the possibility
of the valve riding up on top of this guide strip.
_d._ The valves must be guided vertically by the valve-rod itself, the
inside end of which must be kept in alignment by the usual form of
tail-rod guide.
The vertical play at these parts should not exceed 1/8 of an inch.
_e._ The surface of valves must be machine faced and accurately fitted
to a plane surface, and be steam tight when in contact with the seat of
steam valve.