Heat Treatment Of Gear Blanks

This section is based on a paper read before the American Gear

Manufacturers' Association at White Sulphur Springs, W. Va., Apr.

18, 1918.

Great advancement has been made in the heat treating and hardening of

gears. In this advancement the chemical and metallurgical laboratory

have played no small part. During this time, however, the condition

of the blanks as they come to the machine shop to be machined has

not received its share of attention.

There are two distinct types of gears, both types having their

champions, namely, carburized and heat-treated. The difference

between the two in the matter of steel composition is entirely in

the carbon content, the carbon never running higher than 25-point

in the carburizing type, while in the heat-treated gears the carbon

is seldom lower than 35-point. The difference in the final gear

is the hardness. The carburized gear is file hard on the surface,

with a soft, tough and ductile core to withstand shock, while the

heat-treated gear has a surface that can be touched by a file with

a core of the same hardness as the outer surface.

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