How to measure a roller?

Learn how to accurately measure roller lengths and diameters for conveyor rollers. This guide covers essential measurements, methods and tools, ensuring proper roller selection and installation.

At Dyno Conveyors, we're committed to manufacturing rollers that are perfectly tailored to your needs. Precise measurement is key to this commitment.

That's why we require accurate measurements of length (OBL & SL) and diameter (roller & shaft). These measurements are crucial for proper roller selection, installation and/or replacement.

Measuring roller lengths

Over Bearing Length (OBL)

This is the measurement from the end of one bearing to the end of the other. This is the most critical measurement to get right, as there are many different makes of bearings and this can affect the length.

While vernier calipers are ideal for accurately measuring roller length, most people don't have large ones on hand. But don't worry! We'll share simple tricks using just scrap wood and a sprinkle of Kiwi ingenuity instead, to help you get the job done.

 Whichever method you use, always ensure the roller remains as straight as possible during measurement, and measure from the absolute end of one bearing to the absolute end of the other.

Using vernier calipers to measure rollers

We've created a step-by-step video explaining how to measure rollers accurately using vernier calipers. For a quick tutorial on reading metric vernier calipers, click here.

And if you don’t have access to a large enough vernier caliper, see some of the following alternative solutions.

Alternative solutions to vernier caliper to measure rollers

Solution #1: Make your own verniers!

1. Cut 3 pieces of straight timber: 2x at approx. 150mm long, and 1x at your approx. roller length plus at least 300mm. Ensure these cuts are square/straight.
2. Place the longer piece of wood parallel to the roller.
3. Put the 2 short pieces of wood at right angles to the longer piece (This is where the straight cuts are important!).
4. Put the roller in the gap – resting the shaft on the blocks of wood.
5. Ensure the short blocks of wood are pushed up against the bearing, and then ensure they are still at right angles to the longer piece of wood.
6. Use a tape measure and check the distance between the blocks of wood!
7. Do the same for the shaft length (see next section for more details about shaft measurements).

Tip: If you are measuring rollers often but don't want to invest in a set of verniers, you might want to set this up a little more permanently. So nail the long piece, and one of the short blocks to a base, and then you only have to shift one block! You could also fix a measuring tape to the long block of wood to save having to find that tape every time.

Solution #2: Quick and easy!

If you don’t have time for setting up homemade wood verniers, you can follow the steps below. Just be aware this method is the less accurate one.

1. Same as solution #1, but just use the 2 smaller blocks or some other spacer.
2. Put the roller in the gap – resting the shaft on the blocks of wood.
3. Mark approx. the centre of the shaft at each end, and then carefully lift the roller out.
4. Carefully measure the distance between the blocks, in line with the marks you have made.
5. Do the same for the shaft length.

Solution #3: Let Dyno do it for you!

If you aren’t sure or it is a very critical measurement, you are welcome to send the roller to our factory and we will happily assess it for you.

Inside Frame (IF or sometimes known as ISF)

When a roller is too worn to measure accurately, has undergone modifications, or you're designing a new conveyor, determining roller length based on the Inside Frame (IF) is a good solution.

The IF measurement is the distance between the inside of the conveyor frame. We typically:

1. Subtract 3mm from the inside frame measurement for the Overall Bolt Length (OBL)
2. Add 15mm to each end of the roller for shaft length on standard spring-loaded rollers

For non-standard mounting configurations (other than spring-loaded rollers, such as female threads, cross drills, etc), contact the Dyno Team for specific guidance, we’re here to help!

Measuring roller diameters

The diameter of a roller is the size of the body of the roller and is most accurately measured using smaller vernier calipers.

However, if you don't have access to these precision instruments, you have several alternative methods at your disposal:

1. You can use one of the previously mentioned measurement methods used for the length of a roller (see previous section).
2. You can simply use a tape measure (though this method is not particularly precise).
3. Or you can use a flexible tape and measure the circumference of the roller, then divide this measurement by 3.14 (π) to obtain an approximate diameter.

When taking these measurements, it's important to note that on a standard roller, the diameter will obviously remain consistent along its entire length. However, if you're dealing with a tapered roller, you'll need to measure both the largest and smallest diameters to get a complete understanding of the roller's shape.

Also, keep in mind that roller diameters are often expressed in metric units, but can sometimes be found in imperial units. To avoid confusion, please clarify which measurement system you are using.

Measuring roller shaft lengths

In addition to the roller length, knowing the shaft length (SL) is also a requirement to ensure the shaft fits properly within the roller assembly. This allows for correct bearing placement and prevents the shaft from protruding or being recessed, which can interfere with other components or hinder roller performance.

To measure this accurately, you can employ the same techniques used for determining the roller length (see previous section) using vernier calipers, the wooden block method or a measuring tape, ensuring the measuring tool is aligned with the very ends of the shaft.

- As standard, we add 15mm to each end of the roller for a spring-loaded roller with a shaft 12mm diameter or smaller.
- For larger shafts (16mm or up), we add 20mm to each end as standard.
- For shafts with a female thread, this usually needs to be the same length as the inside frame measurement to fit properly.

As always, if you aren’t sure just ask and we can advise and accommodate most requests.

Measuring roller shaft diameters

Roller shafts usually come in two primary configurations: round and hexagonal.

Round shafts

Simply measure the diameter in the same manner you would measure the body of the roller. Use your vernier calipers if you can for a most precise reading.

Hexagonal shafts

For hexagonal shafts, instead of capturing a diameter, you'll measure across the flats (the widest points between the parallel sides of the hexagon). You have multiple tools at your disposal for this task: a tape measure, standard ruler or vernier calipers will all work effectively.

For more information on non-standard shaft options (such as threaded, flats, cross drills, slots, circlip grooves) and how to measure them, contact the Dyno Team who will be able to help!

You may also be interested in these extra resources:

- Dyno’s extras & custom rollers product page

- Dyno’s bearing types and range

- For information on non-standard tube options (such as grooves tapers/conical rollers), and how to measure them, contact the Dyno Team who will be able to help!

And as always, if you're unsure about any measurements or need assistance, our expert team is always ready to help. Please contact us at enquiry@dyno.co.nz or call 0800 144 044.