Mandrel-drawn brass tubing,
1/16-inch thick, may be selected. If you cannot get this turned off at the
ends in a lathe, mark the lines round it for working to with the aid of a
perfectly straight edged strip of paper, 2-13/16 inches wide, rolled twice
round the tube. The coils must lie exactly under one another. Make plain
scratches at each end of the paper with a sharp steel point. Cut off at a
distance of 1/16-inch from the lines, and work up to the lines with a file,
finishing by rubbing the ends on a piece of emery cloth resting on a hard,
true surface.
[Illustration: FIG. 56.-Cylinder standard before being bent.]
A square-cornered notch 1/8 inch deep and 7/8 inch wide must now be cut in
each end of the barrel, the two notches being exactly in line with one
another. These are to admit steam from the steam ways into the cylinder.
Cylinder Standards.-Use 5/64 or 3/32 inch brass plate for these. Two pieces
of the dimensions shown in Fig. 56 are needed. Scratch a line exactly down
the middle of each, and a cross line 1/2 inch from one end. The other end
should be marked, cut, and filed to a semicircle.
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