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How to measure a drive belt

Working out the drive belt that you require can be a bit tricky but hopefully with these tips you will be able to get there. The first thing to do is try and work out which type of drive belt that you have. If you haven't already done so please take a quick look at our types of drive belts. If you know the type of drive belt you have and you also have numbers on your belt then that should be enough for us to find a replacement belt for you, However for some forms of belts a quick measure is also worth doing as in recent years some imported drive belts have incorrect or conflicting numbers on them.

Vee Belts

Working out which type

Vee belts are generally quite straight forward but you need to check the width at the top quite carefully. Due to wear a vee belt will lose some of its width so it's always worth looking at how high up the pulley the belt sits. Ideally the top surface of the belt should be just above your pulley lip, if it is below then the top edge of the belt has worn. If you can at this point just measure across the pulley where the belt sits. This will give you a fairly accurate idea of the width of belt that you require. The next thing is to measure the depth of your belt and remember it's the height of the belt and not the length of the side of the belt. Next comes working out how to get the length. Work out the length of a V belt Now even if you have numbers on your belt that can still mean 3 different lengths. A Vee belt can be measured by it's inside length, it's overall length and also it's cord length (working length). If your belt has snapped then just measure it end to end. This will give you the La measurement. If your belt is still in use and you don't want to cut it in half to measure it then if practical make it as good a circle as possible and measure across from the inside edge to the inside edge. With this diameter measurement multiply it by 3.142 and you will have the Li measurement of the belt. If your belt is too large for this then you may have to run a soft tape around the outside of the belt to give you the La measurement. Whatever method you use as long as you let us know we should be able to work out the belt you require. Take a look at our vee belt page and you may be able to tell us the style of vee belt you require.

Toothed drive belts

Measuring a toothed belt is made up of 3 measurements. The length, the width and the style of tooth. If the belt has snapped then measure it end to end. If your belt is still intact and is no longer useable then cut it in half to measure it. If it is still in use then with a soft tape measure around the outside. You could run something else around the outside but try and use something that doesn't stretch. You can then measure that item to get your length. Now that you have the length you will need to work out which tooth formation you require.
First of all don't be surprised if you have an imperial drive belt no matter where your machine was manufactured.

Tooth pitch

If your belt is relatively short then the easiest thing to do is count the number of teeth that you have. You can then take the length and divide it by the number of teeth that you have. This will give you the pitch. There are far too many pitch possibilities to explain here but as long as you can tell us the number of teeth and the length that is normally enough.

Tooth style and height

Take a look at the teeth on the belt from the edge of the belt and see if they are rounded or square. Knowing this will really help us. The last thing is to measure the depth of the belt as accurately as possible. With this information you can either fill out our contact form or give a call.

Flat drive belts

Flat drive belts are either rigid or stretchy but measuring them is much the same. On a stretchy belt which are normally not that long and because they are stretchy you have a little bit of room for error you have two choices. Cut in half and measure end to end or form the belt into a circle and measure the diameter. Next measure the width and lastly the thickness is also good to know. If your flat belt is rigid when pulled then the length will normally have to be very accurately measured. End to end laid flat is really the best way but if your belt is still in one loop then we would really recommend you send us a sample. Last but not least we just need the thickness but we only actually need approximately within a mm or so.

Round belts

To measure your round belt just measure end to end and the material thickness. If your round drive belt is still in a loop then the diameter measured inside to inside will do. From this we can make up a belt to your required length. If you think your belt has stretched then let us know and we can always produce slightly smaller as there will be a bit of stretch on the replacement round drive belt.

Poly V Multi Vee drive belts

To measure a poly V drive belt is easiest if you can just measure end to end. Then measure the width and then how many raised ribs across the belt. This will tell us everything we need to identify your belt. The problem comes with the small polyurethane drive belts found on many planers and belt sanders. These are very tricky to measure and a lot easier to offer up against another belt. We really recommend that you send us a sample have a good look for a model number on your machine and we may already know which belt you require.

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