What is Module 3 Gear?
As you can see, "Module 3 Gear" is a gear with a module value of 3.
A Module is a unit of gear tooth size determined by ISO. The larger the value, the larger the tooth size, and the more torque it can withstand.
When meshing a gear pair correctly, if the module of one gear is 3, the module of the opposite gear must also be 3.
Module Calculation :
The size of a tooth can be expressed in terms of the size of the pitch (p), which is the distance between the teeth, and the formula is as follows.
p = dπ / z (d is the pitch circle diameter, z is the number of teeth)
In this case, the calculation is complicated because the formula includes pi.
Therefore, p is divided by π (omitting π), and d / z, which is a round number, is called the module (m) and is used as the unit of tooth size.
m = d / z
For example, if the pitch circle diameter (d) of a gear is 120 and the number of teeth (z) is 40, 120 / 40 = 3, resulting in a module of 3. (As mentioned above, the module is calculated by dividing the pitch by π, so the pitch in this case is 3 × π = 9.42478)
Although the unit of the module is mm, the actual unit is almost always expressed only numerically, without adding mm.
Diametral pitch :
Diametral pitch (DP) is a unit used in the U.S. and other countries that uses inches as a unit of length to express the size of gear teeth, rather than the modules based on the metric system described above.
The module and diametral pitch can be converted using the following formula.
m = 25.4 / DP
For example, if the module is 3, the diametral pitch is 8.46667.
As can be seen from the formula, the larger the diametral pitch, the smaller the module.
Summary - Conversion to other tooth size units other than module :
Module: 3
Circular pitch: 9.42478
Diametral pitch (DP): 8.46667
Tooth height :
The tooth height of a gear is determined by the size of the module (m).
Below is a calculation of the tooth height of a gear with a tooth profile which is standard full depth and module 3 as specified by ISO and JIS (Japanese Industrial Standards).
The calculations of tooth height (h = 2.25m), addendum (ha = 1.00m), and dedendum (hf = 1.25m) for module 3 gears are as follows:
h = 2.25m = 2.25 x 3 = 6.75mm
ha = 1.00m = 1.00 x 3 = 3mm
hf = 1.25m = 1.25 x 3 = 3.75mm
