Full resolution (JPEG) - On this page / på denna sida - Gear Teeth - Approximate construction of involute teeth
<< prev. page << föreg. sida << >> nästa sida >> next page >>
Below is the raw OCR text
from the above scanned image.
Do you see an error? Proofread the page now!
Här nedan syns maskintolkade texten från faksimilbilden ovan.
Ser du något fel? Korrekturläs sidan nu!
This page has never been proofread. / Denna sida har aldrig korrekturlästs.
39° GEAR TEETH.
When gear teeth are constructed as shown in Figs. 6 and 7,
the line g h is 75j^ degrees to the line c f, and the line c i is
\A.y
2 degrees to the line c f. (See Fig. 5),
#
Fig. 7. Involute Teeth (Cut).
The line h g will always be tangent to the base circle,
which is concentric to the pitch circle. The diameter of the
base circle is always 0.968 times the diameter of the pitch circle.
The circle forming the shape of the tooth must always have its
center on the circumference of the base circle, and its diameter
will be one-fourth of the pitch diameter of the gear. As shown
in Fig. 5, the same circle gives the form of tooth for coarser or
finer pitch. When gears are drawn by this method the pitch
circle is divided into as many teeth and spaces as there are to
be teeth in the gear ; then the form of the tooth is simply struck
by the dividers, always using the periphery of the base circle as
center, and always taking the distance in the dividers equal to
one-fourth of the radius of the pitch circle.
The diameter of the base circle is 0.968 times the diameter of
the pitch circle, because cosine of 14^ degrees is 0.96815. The
diameter of the circle forming the shape of the tooth is 0.25 times
the diameter of the pitch circle of the gear, because sine of 14^
degrees is 0.25038. If the line of pressure is laid at any other angle
<< prev. page << föreg. sida << >> nästa sida >> next page >>
