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

*first. Any gear system, the pitch circle is the*

**meaning of pitch**

circlecircle

**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

teeth.

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

etc.**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

gear

salesperson or mechanical engineer the diametral pitch of the

gear needed in order to make sure that the proper type of gear

is

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

gear’s.

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.