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How to Measure a V-belt

V- Belts are incredible industrial utilities for applications such as transmitting power, generating motion, and tracking the relative movement of objects. However, like other machinery components, they are susceptible to wear and tear and require maintenance and replacement to keep the system working optimally. 

To replace your current V-belt, you will need to know its measurements. This article explains how to measure your V-belt and determine its type to help you get the best fit for your system.

Method

You don't measure a V-belt (or any other belt for that matter) using a ruler or steel tape measure. It is also wrong to fold the belt in half, measure its length, then multiply it by two. Another wrong way to do it is folding the belt in half then measuring its length. The most accurate way to go about it with a V-belt measuring tool. If you don't have one, a cloth tape measure should suffice.

You could also wrap a small string around the belt then measure its length with a regular ruler. When using a cloth tape measure or string, ensure the V-belt is under slight tension and that the cloth is tight wrapped against the back of the belt.

How to Measure and Determine Various Types of V-belts

There are three main types of V-belts including:

a) Classical V Belts

These are the original power transmission belts with profiles of M, Z, A, B, C, D & E. They can also be cogged or notched, in which case they go by the profile ZX, AX, BX & CX.

To determine which classic V-belt you have, measure the inner circumference and express it in inches. This will tell you your belt type. For instance, a B-belt with an internal length of 26 inches will be referred to as B26.

Although rare, there are some cases where belts are marked based on their outer circumference. You should, therefore, double-check the measurement used if you are buying from a manufacturer you don't know.

b) Narrow Section V Belts 

These include the SPZ, SPA, SPB & SPC belts. Their cogged equivalents are XPZ, XPA, XPB & XPC belts, referred by some manufacturers as SPZX, SPAX, SPBX & SPCX.

For the narrow section V Belts, you identify them with their pitch length. To obtain the pitch length of a V-belt, you will measure its inner circumference then add a specific number depending on the type of belt, as shown below:

  • SPZ - 13mm
  • SPA - 18mm
  • SPB - 22mm
  • SPC - 30mm

 

c) Narrow Section Imperial V Belts

Imperial V Belts are identified in the same way as classical belts, where you measure their internal circumference and express it in inches. For instance, a 3V450 has an inside circumference of 45 inches, whereas a 3V400 has an internal circumference of 40 inches.

Well, that is all there is to measuring and identifying a V-belt. Remember to take your measurements at least twice for more accuracy. Hopefully, this guide will make it easier for you to determine the belt you need. Good luck!