Explanation Of Pitch And Metric Module Of Spur Gears With Calculators

Like every machine element, spur gears have also manufacturer standards. One of the most important standards of spur gears is the term called ‘pitch’. But pitches of spur gears are generally used in US customary unit system. The counterpart of the pitch of spur gears in the metric system is the term called ‘metric module’. Standard gears are produced with standard metric modules or pitches.

In this article, we explain the calculations, types, and conversions between different pitch values and metric modules.

To calculate different pitches of a spur gear, we need to understand the term ‘pitch diameter’.

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What Is Pitch Diameter Of Spur Gear?

When we consider two contacting spur gear-pair, we can find out the pitch diameters of these two gears.

Pitch diameter illustration(Source Of Image: Robert L. Mott, Machine Elements For Mechanical Design).

The pitch diameter of two assembled spur gears is the tangent diameters that are shown above illustration. In a spur gear pair, one of the spur gears is driven and another one is driving gear.

How To Calculate Pitches Of Spur Gears? What Are The Types Of Spur Gear Pitches?

In spur gear terminology, there are two types of spur gear pitch values are used. These pitch values are; Diametral Pitch and Circular Pitch.

  • Diametral Pitch Calculator: Diametral pitch values are the most used pitch value in spur gear terminology to classify the spur gear standards. It is generally used in inches. It is calculated by the division of the pitch diameter of spur gear(Dp) to the number of teeth(N).

Diametral Pitch Calculator For Spur Gears












You can use the calculator above to calculate the diametral pitch of an individual spur gear. You just need to enter pitch diameter(inches) and the number of teeth. Then click on the ‘Calculate!’ button to calculate diametral pitch in inches. Click on the ‘Reset’ button to calculate other calculations.

In spur gear standards, diametral pitch values are given as integers. You can select a spur gear according to these standards. Diametral pitch standards for spur gears are generally used in countries where US Customary Units are used.

  • Circular Pitch Calculator For Spur Gears: Circular pitch is another kind of standard that is not frequently used as diametral pitch. Circular pitch can also be calculated by the multiplication of diametral pitch with π, for individual spur gears.

As you must understand that, two gear mates in spur gear systems must have the same pitch.

What Is the Metric Module Of Spur Gears?

In SI units, the counterpart of pitch standards for spur gears is the term ‘metric module’ which is stated with ‘m’. The unit of the metric module must be millimeters.

The calculation of the metric module is the same with diametral pitch. But, you need to consider the pitch diameters in millimeters. After converting the pitch diameter value to millimeters, you can use the calculator above to calculate the module of your gear.

Gear manufacturers generally use integer values of modules when they produce their spur gears.

You can use the MB-Unit Converter tool to convert your units between US Customary and SI.

Diametral Pitch To Metric Module Conversion For Spur Gears

If you have the diametral pitch or metric module to convert it to another one, you just need to know that you need to make a conversion between inches to millimeters.

To obtain the metric module value of a spur gear, you need to divide 25.4 to the diametral pitch value of the spur gear. To obtain diametral pitch, you need to do vice-versa.

Conclusion For Pitch And Metric Modules Of Spur Gears

This is a very important thing that you need to know about spur gears. Sometimes, you need to select a spur gear from diametral pitch catalogs, and sometimes from metric module catalogs.

Also, you can take a look at the other useful engineering calculators available in Mechanicalland.

Mechanicalland does not accept any responsibility for the calculations made with calculators by users. A good engineer must do hand calculations to check the calculations done in calculators.

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4 Comments

  1. Under “How To Calculate Pitches Of Spur Gears? What Are The Types Of Spur Gear Pitches?
    In spur gear terminology, there are two types of spur gear pitch values are used. These pitch values are; Diametral Pitch and Cicular Pitch.”

    You should change “Cicular” to Circular.

  2. Similarly, under Diametral Pitch Calculator For Spur Gears change the spelling in “Enter Pitch Diamater:” to Diameter.

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