If your equipment has a worn or broken pulley, you may not know where to begin when ordering a new one. Fortunately, you’ve come to the right place to learn about buying pulleys online.

For some reason, many people believe that metal sheaves and pulleys last forever – until they don’t. However, you can track many belt drive problems back to an issue with a metal component.

The only solution for getting rid of a belt noise that sounds like trouble is to replace a worn pulley. Usually, this kind of malfunction is a result of premature failure.

When a synchronous belt drive gets closer to the end of its life cycle, it starts to show wear at the base of its teeth. Then, cracking will start the show on the forward side of the tooth in the direction that the belt travels. When this happens, it’s time to look for pulleys online for sale.

To learn what you need to do before buying pulleys online, keep reading.

Sizing Things Up

Before you order the replacement part for your pulley system, you need to know what size to order.  Then, you can start looking for suppliers – more on that shortly.

You’ll need to measure the important dimensions of the damaged pulley or sheave. This information will help you find the best replacement that’s available. Once you record the dimensions of the worn pulley, you’ll know what information to give to the supplier.

Typically, you’ll need to measure the outside diameter, inside diameter, and width of the pulley. There are, however, other measurements that are good to know to help you find the perfect replacement.

As with any project, you’ll need the right tools for the job. The tools for this job, however, are pretty fundamental.

You can measure your pulley with a measuring tape or ruler. However, a caliper is more accurate. If you’re replacing a flat idler pulley and you don’t have a caliper, however, you’ll also need some string to measure the inside circumference.

Pulley Versus Sheave: What’s the Difference?

As an aside, people often use the words pulley interchangeably. However, they mean two different things.

A pulley without a sheave changes direction whichever way you apply force. The pulley can help to move a heavy load, but it doesn’t apply more force than you transfer to it.

A pulley with a sheave, however, provides mechanical leverage. You only need half of the original force for each sheave that’s in a pulley.

Sheaves do more work, but they also create more friction. As a result, they’re susceptible to wear.

Start With the Outer Diameter

You must find a pulley that matches OEM specifications as closely as possible to ensure the proper operation of your machinery. With the right information, you can get it done quickly.

Begin by laying the old pulley on a flat surface. Now, place your ruler or caliper on top of the pulley.

Make your measurements carefully. Ensure that you measure across the exact center of the pulley.

One way to measure precisely with a ruler is to hold it still and rotate the outer edge of the pulley. Note the measurement of the pulley as you turn it. The right dimension is normally always the longest measurement that you read as you rotate the pulley.

Measuring the Pulley Flat

If you’re replacing a flat idler pulley, you’ll need to find the measurement of the flat diameter. Again, you only need this measurement if you’re replacing a flat idler pulley.

The flat is the diameter of the pulley that holds the belt. If your flat idler doesn’t have belt flanges, then the flat diameter is the same as the outside diameter.

If it does have flanges, then the flat diameter is smaller than the outer diameter. You can estimate the flat diameter by measuring it the same way as you did the outer diameter.

However, you have to use your imagination. Pretend the pulley doesn’t have flanges and measure that circumference.

If you can’t eye it out, no worries. There’s one more trick that you can try.

Grab your string and wrap it tightly around the pulley in the belt track. Now, make a mark where the string overlaps.

Next, measure the length where you made the marks. Finally, divide the length by 3.14.

Figuring Out the Flat Widths

Now, you’ll need to measure from side to side where the belt rests. This area is between the inside edges of the pulley.

It’s important not to confuse the width of the pulley with the width of the hub. These are two different measurements.

The pulley flat width is also called the belt width. Again, you’ll only need this measurement if you’re replacing a flat idler pulley.

The best tool for this measurement is a caliper. If you don’t have one, you may want to buy one, especially if you’re repairing mission-critical equipment.

If you’re determined not to use a caliper, you can. Measure the width between the flanges from the inside edges with your ruler and do your best to eyeball the measurement.

With some flat idlers, however, using a ruler to eyeball the measurement can prove challenging. You may have trouble making this measurement with a ruler on a flat idler with angled flanges.

Angled flanges help the belts to last longer. However, they also make measuring the flanges especially challenging without a caliper.

Don’t Forget to Size up the Shaft

Finally, you’ll need to measure the inside diameter of the pulley to match the shaft. Online pulley retailers may use several names to describe this measurement, such as:

  • Bolt size
  • Bore
  • Center hole
  • Shaft size

Measure across the center hole of the pulley, exercising caution not to measure across the keyway. The keyway is a small cut out that locks the shaft in place.

Alternatively, you may already know the size of the shaft. For instance, if you know that your equipment uses a one-inch shaft, that’s the inside diameter of the pulley. Therefore, you can assume that the size of the shaft equals the inside diameter of the pulley.

Armed with your specs, you’re ready to look for pulley suppliers. Begin by searching for suppliers with an acceptable return policy. If pulley manufacturers or suppliers facilitate returns, they’ll usually state it clearly on their website.

Choosing a Supplier When Buying Pulleys Online

Now that you’ve narrowed down your choices, you may want to find a supplier that’s one of the top pulley manufacturers, especially if your equipment is unique. They can likely make a custom pulley should you need one. At the least, you’ll have found a skilled and knowledgeable provider for buying pulleys online in the future.

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