Skip to content


Your cart is empty

How to Measure a Pulley for a Replacement Part

Do you know how to accurately measure your pulley for a replacement part? When the time comes to replace your important equipment, a solid understanding of basic measurement procedures is invaluable. In the content below, we walk through the most common pulley measurements and how to accurately gather these dimensions when a precise replacement is required.

Most Important Pulley Measurement Tools

Before measuring, we recommend gathering a few important tools:

  • Measuring tape
  • Ruler
  • Calipers

Although not critical, calipers are helpful for highly accurate measurements.

How to Take Primary Measurements of a Pulley:

1. Measure Tooth Pitch and Number of Teeth

Measuring the tooth pitch will assist in confirming the correct tooth profile. Using the most accurate tool available, measure from the crown of one tooth to crown of the next tooth. This measurement is the tooth pitch. Other information that will assist in finding the tooth pitch and profile is the part number of the timing belt running on the pulley. Count the number of teeth on the pulley.

2. Measure Pulley Face Width

Measuring pulley width is relatively simple. Begin by holding your pulley vertically to expose the flat side, and measure from outside edge to outside edge with a ruler.

3. Measure Pulley Between Flange Width

Also known as belt width, this measurement is only required for pulleys with flanges. Once again, use calipers for utmost accuracy. If using a ruler, measure from inside edge to inside edge along the pulley’s teeth and visually estimate the measurement.

Calipers allow for a more accurate reading of the distance between the inside edges.

4. Measure the Bore Diameter of the Pulley

The pulley’s bore is also known as the inside diameter, center hole, and shaft size. To collect inside diameter, simply use a ruler to measure the center hole of the pulley.

Measuring the bore is unnecessary if you already know the shaft or bolt diameter. For example, if your pulley runs on a 2” shaft, the inside diameter is also likely 2”.

5. Measure the Pulley Hub Length

Using a ruler, measure the distance from the front of the hub to the first flange.

6. Measure the Pulley’s Keyway

The keyway is the section where your key is inserted to lock the pulley in place. Most often found in a drive pulley’s inside hole, the keyway can be measured in three primary ways.

The most accurate method is by measuring your key. Although not as accurate, a ruler can be utilized as well. Finally, you can estimate the keyway size based on shaft size.

7. Measure the Pulley Throughbore

Finally, measure your pulley throughbore. As the dimension implies, you will be utilizing a ruler to measure through the pulley bore. To gather an accurate reading, simply measure your bore from one end to the other.

Illinois Pulley and Gear

At Illinois Pulley and Gear, we are timing pulley experts, regularly manufacturing high-quality timing pulleys according to customized specifications. If you are in need of a pulley replacement, simply send us your dimensions or the part itself, and we will recreate the precise part you need.

Located in the Chicagoland area? Our team is ready to drive to your location and perform measurements before the replacement is needed, allowing your business to run without a hiccup.

To learn more about how we can best service you, please do not hesitate to give us a call at 847.407.9595 or complete our online contact form. A team member will be in touch shortly!