The rim of the disk is divided into 53 equal parts and radial
lines drawn from rim to line B, indicating the depth of the slots.
Slots are cut in the disk with a hacksaw on the radial lines. A
small vise is convenient for holding the disk while cutting the
slots.

When cutting the disk out of the rough brass, sufficient margin
should be left for filing to the true line. The slots should be
left in their rough state as they have a better hold on the pens
which are used for the blades. The pens are inserted in the slots
and made quite secure by forcing ordinary pins on the inside of
the pens and breaking them off at the rim, as shown in Fig. 4.

When the pens are all fastened two pieces of metal are provided,
each about 1 in. in diameter and 1/32 in. thick, with a 3/8-in.
hole in the center, for filling pieces which are first placed
around the shaft hole between the disk and side plates C, Fig. 1.
The side plates are then secured with some of the 1/8-in. machine
screws, using two nuts on each screw. The nuts should be on the
side opposite the inlet valves. The shaft hole may also be filed
square, a square shaft used, and the ends filed round for the
bearings.

The casing for the disk is made of two enameled-iron saucers, Fig.
2, bolted together with a thin piece of asbestos between them to
make a tight joint. A 3/4-in. hole is cut near the edge of one of
the saucers for the exhaust. If it is desired to carry the exhaust
beyond the casing, a thin pipe can be inserted 1/4 in. into the
hole. Holes are drilled through the pipe on both inside and