Measuring A Synchronous Belt

We get a lot of questions from people trying to find a suitable replacement belt. There seems to be a lot of confusion as to what information they need to provide for us to try to ID the particular belt. It’s not as difficult as it seems. The first question that we are going to ask you is to get us any print on the back of the belt. Industry callouts are pretty similar, and if you can find a part number, a lot of times we can ID it from that alone. Now if it comes down to measurements, there are only a couple that we need: length, width, and pitch. We also need to know the shape of the teeth. This is pretty simple, as there are only about 3 different types that we can interchange for power transmission belts; square/trapezoidal, half circle, and curvilinear with a flat spot on the top of the tooth. These shapes help us ID the type of belt, from here, all we need are the other three measurements to really get going.

Length: measure the outer circumference of the belt. If the belt is broken in half, just measure the total length.

Width: measure the width across the back of the belt. This could be in metric or imperial units; it doesn’t matter which one you give us, we just need the best measurement you can get.

Pitch: measure from the center of one tooth to the center of the next tooth. Simple, but sometimes the teeth are small. Getting as close as possible on this really helps – see above about the metric/imperial units issue.

We will also ask you to count the teeth, it’s not that we don’t trust your measurements, but this is verification of the correct length and pitch measurements. I know, I know… There may seem to be a lot of them, but even a belt with 200 teeth will only take a minute or two to count.

That’s it, from here, all it takes is knowledge of our product line to ID the type of belt, and a catalog to see if it’s a stock size. Sometimes we can’t cross a belt because it was made special for someone. In these cases you will have to go back to the manufacturer of the machine that your belt came on – even if we made the belt in the first place.