How to Measure a Caster Stem

We've noticed that one of the biggest frustrations amongst our customers is getting the wrong stem on a caster. We've put this guide together to help explain how to correctly measure caster stems, so you get the right caster the first time.

Stem Types

To start, we need to know what we are measuring, as each stem is measured slightly differently. Here is a list of common stem types:

Grip Ring Stem

Made with round stem that has been milled with a race on the insertion end. The end is wrapped with a brass or wire band which locks the stem in place. It is most common on chairs and ready-to-assemble furniture.

Threaded Stem

A threaded stem, as the name implies has a thread, like a bolt. Threaded Stems are most commonly found on plastic and metal equipment, such as small carts. Threaded stems are also found on some chairs.

Grip Neck (Wood) Stem

Used almost exclusively on wood furniture, the grip neck stem has a milled insertion end that is captured by the socket. If you have a grip neck stem, they only come in one size, you are in luck. Look for a listing with a W524 stem code, that's the one you need. So you can stop right here, you're done.

Measuring the Stem

Now that we've identified the stem type, we can measure the stem. You will need a ruler and an adjustable wrench.

Grip Ring Stem Grip Ring stems are measured by their diameter and length, for example 7/16" diameter x 7/8" long. To measure the diameter, use an adjustable wrench. Take the wrench and tighten it down gently across the stem. The gently removing it, measure the gap in the wrench and you have the diameter. In the US, generally speaking, the only sizes available are 3/8" and 7/16" diameter. Some metric sizes exist but are generally interchangeable with their standard counterparts. Now that we have the diameter, we need to measure the length. The length can be measured by taking a ruler from the butt-end of the stem (the part at the bottom) and measuring to the top. With these two measurements you'll have the right caster the first time.

Use an adjustable wrench to gauge the diameter of the grip ring stem.	Measure the gap in the adjustable wrench, this is the diameter of the grip ring stem.	Measure the length of the grip ring stem with a ruler from the bottom (butt-end) to the top.
Threaded Stem Threaded stems come in many sizes, ranging from 1/4"-20 to 3/4"-10 and everything between. Threaded stems are sold by their thread diameter and the length. To measure the diameter of the stem use an adjustable wrench. Gently tighten down the wrench across the diameter of the stem. Now, remove it gently and measure the gap. This will be the diameter. Unlike grip ring stems, where only two sizes exist, many different diameters exist, so double check your measurement. To measure the length, take a ruler and measure from the butt-end of the stem (the part at the bottom) and then to the top, it's that simple. Now you have the two measurements and can choose the caster that best fits your needs.

Use an adjustable wrench to gauge the diameter of the threaded stem.	Measure the gap in the adjustable wrench, this is the diameter of the threaded stem.	Measure the threaded stem length with a ruler from the bottom (butt-end) to the top.

For a printable Adobe PDF version, click here.

Requires Adobe Acrobat Reader, available free through this link.