evel so that there is no lifting of
heavy pots. Fuel oil is used in all the furnaces and gives highly
satisfactory results. The consumption of fuel oil is about 2 gal.
per hour per furnace.

The work is packed in the pots in a room at the entrance to the
heat-treatment building. Before packing, each gear is stamped with
a number which is a key to the records of the analysis and complete
heat treatment of that particular gear. Should a question at any time
arise regarding the treatment of a certain gear, all the necessary
information is available if the number on the gear is legible. For
instance, date of treatment, furnace, carburizing material, position
of the pot in the furnace, position of gear in pot, temperature of
furnace and duration of treatment are all tabulated and filed for
reference.

After marking, all holes and parts which are to remain uncarburized
are plugged or luted with a mixture of kaolin and Mellville gravel
clay, and the gear is packed in the carburizing material. Bohnite,
a commercial carburizing compound is used exclusively at this plant.
This does excellent work and is economical. Broadly speaking, the
economy of a carburizing compound depends on its lightness. The
space not occupied by work must be filled with compound; therefore)
other things being equal, a compound weighing 25 lb. would be worth
more than twice as much as one weighing 60 lb. per cubic foot. It
has been claimed that certain compounds can be used over and over
again, but this is only true in a limited way, if good work is
required. There is, of course, some carbon in the compound after
the first use, but for first-class work, new compound must be used
each time.

THE PACKING DEPARTMENT.--In Fig. 56 is shown the packing pots where
the work is packed. These are of malleable cast iron, with an internal
vertical flange around the hole _A_. This fits in a bell on the
end of the cast-iron pipe _B_, which is luted in position with
fireclay before the packing begins. At _C_ is shown a pot ready
for packing. The crown gears average 10 to 12 in. in diameter and
weigh about 11 lb. each. When placed in the pots, they surround
the central tube, which allows the heat to circulate. Each pot
contains five gears. Two complete scrap gears are in each furnace
(_i.e._, gears which fail to pass machining inspection), and at
the top of front pot are two or more short segments of scrap gear,
used as test pieces to gage depth of case.

[Illustr