The mirror., 1922-04-27

the size of the gear rolled, it is apparent
that advance of the die per revolution is
very slight. This assures very thorough
kneading and working down of the metal
Of the blank and permits the metal to
flow evenly and freely. The fact that
both die and blank are positively driven
and accurately synchronized assures the
die teeth penetrating the blank radially in
exactly the same position on each revolu-
ton, and entirely eliminates any slippage
or tooth distortion in the finished product.
During operation the die is cooled by a
stream of water directed against its face
at point farthest from contact with the
hot blank. Through the entire process,
consuming only few seconds, the tenn
perature does not rise above heat easily
bearable to the hand The chilling effect
of the comparatively cold wet die on the
heated blank causes sudden contraction
and consequent loosening of the scale
formed, which is then thrown off by the
centrifugal force resulting from the high
speed of operation. Since the rolling is
continued until the blank has cooled below
the critical temperature, or in other words
until after the formation of forging scale
has ceased, the finished product of the
process is entirely free from scale and the
formed teeth are not only perfectly shaped
but are also highly polished on all contact
surfaces. This fact, of course, eliminates
any necessity for further finishing oper-
ahons, except on the bore and faces or the
these operations, which may be easily and
semi automatically performed, the gears
are chucked on the accurately rolled teeth,
thus assuring perfectly accurate centering.
In order to assure the highest possible
degree of precision of tooth form, machines
designed for the production of extremely
accurate and perfect gears are equipped
with additional mechanism for frequently
and automatically reversing the shafts
carrying the die and blank. This frequent
automatic reversing or oscillation, at
somewhat reduced speed, varying from
about 80 to about 200 r. p. n.y. during the
forming of the teeth and nearly to the
point of full engagement, assures displace- :.
ment and building up of the metal to an
equal degree on both sides of the teeth,
producing an absolutely symmetrical tooth.
The full cycle of operations of the oscillat-
ing type machine, automatically controlled,
is as follows:
High-speed direct rolling, the die roll
advancing to positive contact with the
gear blank.
Oscillating rolling at reduced speed UNI
til the teeth of the die roll reach within
about 0.O1O in. of full depth.
Planishing by high-speed direct rolling
until the die-roll teeth engage the gear to
full depth.
High-speed withdrawal of the die roll.
The die rolls are somewhat narrower
than the gear blanks and the effect of this
is the production of gears which are par
TALLY or fully shrouded. Consequently if
it is desired to strengthen the weaker men,
Der of pair of gears, the shroud may be
left on, either entirely or partially, or the
shrouds on the two gears may be so pro-
portioned as to equalize the strength of the
two and greatly increase that of the COM
The degree of this incrse.e in
strength cannot well be accuf--- Ter
mined, but considering the page 4, Col y