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TRUCK SERVICE MANUAL
TM 5-4210-230-14&P-1
GENERAL INFORMATION
Gear Tooth Parts
The outside diameter of a gear is the diameter
measured over the top of the teeth.
The root diameter of a gear is the diameter measured
at the bottom or roots of the teeth.
The center distance is the distance between the centers
of two meshing gears, the pitch circles of which are tangent to
each other.
The diametral pitch of a gear is the number of teeth for
each inch of pitch diameter, and is found by dividing the
number of teeth by the pitch diameter.
The circular pitch is the distance from the center of one
tooth to the center of the next, measured as an arc along the
pitch circle.
The working depth is the depth to which the teeth in a
meshing gear enter into the spaces between the teeth of the
opposing gear.
The clearance is the amount by which the tooth space
is cut deeper than the working depth.
The face of the tooth is that part of the tooth curve that
is between the outside circumference and the pitch circle.
The flank of the tooth is that part of the working depth
of the tooth which comes inside of the pitch circle.
Gravity
The attraction of bodies toward the center of the earth.
Under the influence of gravity alone, all bodies fall to the earth
with the same velocity and with the same acceleration. The
acceleration increases with the latitude and decreases with
the elevation above the level of the sea. Its value at the level
of the sea in the latitude of New York is 32.16 feet per second.
(In the metric system, Gravity equals 9.81 meters per second
at 45 degrees latitude and sea level.)
Hardness
Is that property of a material by virtue of which it resists
penetration.
Helix
A spiral. A coiled spring or a screw thread forms a
helix.
Also, a spiral cut on the side of injection plunger for
metering fuel.
Hydraulics
The science dealing with liquids in motion.
Hypoid
Hypoid (contraction of the word hyperboloid) meaning
that the pinion is offset with respect to the center line of the
ring gear.
Inch-Pounds
A term used to denote work or energy.
Land
One of the sharpened ridges which make up the cutting
section of a tap, die, reamer or milling cutter after the flutes or
chip clearance spaces have been removed.
Lead
The longitudinal distance which a screw thread
advances when turned one complete revolution.
Horsepower
Horsepower (abbreviated H.P.) is the unit of power
adopted for engineering work. One horsepower is equal to 33,
000 foot-pounds per minute, or 550 foot-pounds per second.
The metric horsepower is equal to 75 kilogram-meters per
second, or 542.5 foot-pounds per second, or 32, 550 foot-
pounds per minute. The kilowatt used in electrical work equals
1.34 horsepower; or one horsepower equals 0.746 kilowatt.
Velocity
Velocity is distance divided by time, and is expressed
in feet per minute, miles per hour, etc.
CTS-2128-L Page 10
PRINTED IN UNITED STATES OF AMERICA
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