Explanation Of Pitch And Metric Module Of Spur Gears With Calculators

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Like every machine elements, spur gears have also manufacturer standards. One of the most important standards of spur gears is the term called as ‘pitch’. But pitches of spur gears are generally used in US customary unit system. The counterpart of pitch of spur gears in 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’.

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)

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 other 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 Cicular 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 divison of pitch diameter of a spur gear(Dp) to number of teeth(N).

Diametral Pitch Calculator For Spur Gears

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

What Is Metric Module Of Spur Gears?

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

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

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

You can use 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 diametral pitch or metric module to convert it to other one, you just need to know that you need to make conversion between inches to milimeters.

To obtain metric module value of a spur gear, you need to divide 25.4 to 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 catalogues, and sometimes from metric module catalogues.

Also you can take a look at the other useful engineering calculators avaliable in Mechanical Base.

Mechanical Base does not accept any responsibility of the calculations that made with calculators by users. A good engineer must do hand calculations to check the calculations done in calculators.

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