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Hacker, Robert W. (ed.) / The Wisconsin engineer
Volume 53, Number 4 (January 1949)

Henke, Russell
Flame-cut gears,   p. 9


Page 9


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                                             by Russell Henke m'49
   One of the most interesting phases of industry is the
constant changing and improvement of methods and pro-
cesses which constitutes progress in the field of manu-
facture. It is by such advancement that we have progressed
from the model T to the modern automobile; from the old
battery radio sets to modern television.
  Again, by technical advancement, the gear and sprocket
industry has been presented with a method of manufac-
turing their products which differs as much from the old
techniques as did the model T from the new car, or the
battery radio from television; namely, flame machining.
Flame machining, as developed by Glenway Maxon, Jr.,
of Milwaukee, Wisconsin, is simply the process of cutting
gears and sprockets from steel plate to a high degree of
accuracy by means of oxy-acetylene cutting torches.
  Before going into a more detailed description of the
flame machining process, let's look at the general pro-
cedure for making a gear or sprocket by the methods
now employed.
  Since most gears and sprockets are cast into blank shape
before being machined, a foundry is necessary with all
its incumbent processes. First the pattern must be made
for the blank; then the mold is rammed up and the neces-
sary cores made and baked. Following this the mold and
cores are assembled, moved to the pouring floor, and the
metal, which first must have been melted, is poured into
the mold. After this the blank must be shaken out of the
mold and cleaned to remove sand and other extraneous
material. Then the risers must be cut off, and finally the
gear or sprocket blank is ready to go to the machine shop.
  The use of all this equipment in the foundry pre-
supposes the initial cost of purchasing the equipment,
upon which is superimposed the maintenance costs.
  In the machining of the gear or sprocket any one of
several methods may be used, such as, hobbing, milling,
or shaping. It seems odd that the actual operation of
machining, which is ordinarily thought of as the making
of a gear or sprocket, should actually constitute only a
fraction of the total operations.
  Now we can take a look at the flame machining pro-
cess, keeping in mind the preceeding description for
comparative purposes.
  The flame cutting machine itself consists of a bed
upon which the driving and cutting components are
mounted. The cutting device is an oxy-acetylene cutting
torch held in a bracket mounted on rollers running on
a track, allowing back and forth longitudinal motion of
the torch relative to the gear or sprocket blank.
  The blank is positioned on a spindle which rotates at
the same time that the torch is moving back and forth,
the two motions being coordinated by a set of cams and
driven through a set of back gears on the machine. It is
the combination of rotation of the blank and longitudinal
motion of the torch that produces the proper tooth con-
tour.
  There are two cams in the set which help to control
the tooth shape; the contour cam and the speed cam.
  The contour cam is accurately plotted from the shape
of the gear or sprocket tooth itself. The torch bracket
is indirectly connected to the contour cam by means of
a pantagraph lever arrangement which rides on the cam.
As the cam revolves, the cam rider roller imparts the
motion to the pantgraph arm which, through the panta-
graph linkage, causes the back and forth motion of the
torch carriage.
  In order that the tooth surface be smooth and not
burned in some places while uncut in others, the torch
should cut at constant speed. This function is performed
by the speed cam, which is plotted from the gear tooth
contour in such a manner that as the torch moves back
and forth radially in relation to the blank and the blank
revolves, the net relative motion of the torch along the
cutting line is constant. In order to accomplish this feat
the speed cam arm is connected to a constant speed motor
drive which varies the speed as required.
                             (Phzoto (oltrusy Cog)nitic Co.)
                     Flame-cut gears.
  The pantagraph linkage mentioned previously is ad-
justable to permit the machining of an infinite number of
sizes of teeth, within the limits of the machine. Fur-
thermore, it is marked so that the exact pitches for
sprockets or gears which are standard today can be set
immediately. This increases the utility of the machine,
since the machining device for large size teeth is the same
as that for a small size tooth.
                   (please ti/llI to  page  18)
JANUARY, 1949
9


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