Practical Significance and Use of Module and Diametrical Pitch

We all aware about ‘ What is Module ??’ and What is
‘Diametrical Pitch’ . Both these concepts are function of pitch
circle .So let us Understand the meaning of pitch
first. Any gear system, the pitch circle is the
imaginary circle that connects the points on the gear
where two interlocking gears meet. The pitch circle divides the
gear’s tooth into the top of the gear tooth , or addendum, and
the bottom of the gear tooth, called the dedendum. At any point
where two gears touch, their pitch circles will be tangent to
one another if the gear system is designed correctly.

Module: (modulus)
Module is a ratio of Pitch circle diameter to total nunber of
teeth on a gear or pinion. The Module have standard values like
4,5,7 likewise, it is not given in fraction at all. Unit of
module is Millimeter.
Practical meaning of Module:
1) Module gives total idea about the Gear size either small or
too large.
2)  Gears are basically designated by using module and
number of teeth ,meaning of this is that If Someone wants to
buy a gear ,he need to ask gear by module and number of
3) As already menstioned Pitch Circle is imaginary circle .we
can’t measure practically to Pitch circle diameter. It can be
found with help of module and teeth .Obviously from formula one
can easily find the pitch circle diameter.
4) while designing gear first module is decided according to
speed ratio and number of teeth. Further this module is used to
calculate remaining gear parameter like addendum ,deddendum
What Is Diametral Pitch?
Diametral pitch is also called as diametrical pitch. Diametral
pitch is reciprocal of module i.e. Ratio of number of teeth to
Pitch circle Diameter.
Diametral pitch, then, is a function of the diameter of the
gear’s pitch circle. It is equal to the number of teeth of the
gear per inch or per centimeter of its diameter,depending on
which measuring system is used. For example, if a gear has 32
teeth and a diameter of 8 inches (20 cm), the diametral
pitch is four teeth per inch or 1.6 teeth per centimeter. When
a consumer purchases or orders a gear, a manager would tell his
salesperson or mechanical engineer the diametral pitch of the
gear needed in order to make sure that the proper type of gear
ordered. When a gear system is first designed, diametral pitch
is important because it helps determine what size and type of
gear is needed to interlock with any other gear.
A gear is designed to transfer power from one
section of a machine to another section of the machine. Two
gears that will interlock successfully need to have the same
measurements or they will not work properly together and the
power will not be
transferred. For example, the ratio of the number of teeth on
one gear to the second gear needs to be the same as the ratio
between the first gear’s diametral pitch to that of the second
This measurement helps determine how fast a gear can move in a
machine as well. The
velocity ratio of a gear is defined as the ratio of the first
gear’s rotation speed to the ratio of the second gear’s
rotation speed. This same ratio also needs to apply to the
diametral pitches of the two gears for the system to
function properly.