diameter; the pistons, H, are ordinary 1-1/2 in. pipe caps turned
to a plug fit, and ground into the cylinders with oil and emery.
This operation also finishes the inside of the cylinders.

The upright rods binding the top and bottom plates are of steel
rod about 1/8-in. in diameter, threaded into the top plate and
passing through holes in the bottom plate with hexagonal brass
nuts beneath.

The valves, C, and their seats, B, bored with a countersink bit,
are plainly shown. The valves were made by threading a copper
washer, 3/8 in. in diameter, and screwing it on the end of the
valve rod, then wiping on roughly a tapered mass of solder and
grinding it into the seats B with emery and oil.

The valve rods operate in guides, D, made of 1/4-in. brass tubing,
which passes through the top plate and into the heavy brass bar
containing the valve seats and steam passages at the top, into
which they are plug-fitted and soldered.

The location and arrangement of the valve seats and steam passages
are shown in the sketch, the flat bar containing them being
soldered to the top plate.

The steam chest, A, over the valve mechanism is constructed of

[Illustration: Engine Details]

1-in. square brass tubing, one side being sawed out and the open
ends fitted with pieces of 1/16 in. sheet brass and soldered. in.