Gears must be made of extremely hard steel, which will be resistant to abrasion, corrosion and mechanical damage. The use of sprockets in various types of machines and equipment requires their selection in terms of technical parameters. From this text you will learn what the sprocket module is and how it is calculated.

**Gear features**

Gears are parts used for machines and equipment to change torque, angular speed and direction. These are the most important components of gears working with a wheel, disc or modular sprocket strip. In each gear, the following are distinguished:

- number of teeth (z),
- split diameter (d),
- vertex diameter (d
_{a}), - foot diameter (d
_{f}), - the diameter of the main wheel (
_{d}b), - circumferential scale (p),
- basic scale (pb
_{}), - tooth height (h),
- tooth head height (h
_{a}), - tooth foot height (h
_{f}), - tooth height factor (y),
- correction factor (x),
- vertex clearance (c),
- tooth module (m).

The module is the size that allows you to determine the dimensions of teeth and gears due to strength conditions. This is a parameter used in the selection of racks to work together. **Regardless of the size of the sprockets, their module must remain the same.** Mismatch leads to incorrect interlocking, which can result in a quick clash of teeth.

**Standardisation and design**

The gear module is a size standardized by the Polish standard PN-ISO 54:2001 General purpose cylindrical gears and for heavy industry – Modules. It is possible to use module values other than those specified in the standard, but this involves the production of custom gear-fit tools with such modules. To calculate the sprocket module, use the formula:

m = ⌀/(T+2).

- m – sprocket module,
- ⌀ – the diameter of the rack,
- T- number of teeth.

Gear modules have been standardized along with graduation parameters, tooth head height, foot height and total tooth height. **The tooth height factor is expressed in times the module. In most cases, normal teeth y = 1 are used.** Below this value are the low teeth used in tapered gears with arched teeth, where the small wheel has a number of teeth from 5 to 10, in worm gears, in gears and in ewolwent multi-key connections. A value above 1 is used in gear pumps. In normal teeth, the head height is equal to the module, and the height of the foot is 1.2 mm. After adding, you can get the total height of normal teeth, that is, 2.2 mm.

**Conversion from an inch system**

This is slightly different in countries that use the inch system. The module is called Diametral Pitch. This is the size that represents the number of teeth of the gear per inch english diameter of the partition wheel. The formula is as follows:

DP = z/d"

- DP – Diametral Pitch,
- z – number of teeth,
- d" – the diameter of the wheel expressed in inches.

The number of teeth can be placed d/m, i.e. the diameter of the subdimeter circle expressed in millimetres by the module. Replace the diameter of the split wheel from inches to millimeters (1 inch English = 25.4 mm). Thus, we get the conversion pattern DP = 25.4/m.