How to Measure a Caster Stem

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

Stem Types

Starting out, 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 stems

Made with a round stem that has been milled with a race on the insertion end. This 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.

Casters
Casters

Threaded stems

As the name implies, it has a thread, like a bolt. They are most commonly found on plastic and metal equipment, such as small carts and some chairs.

Grip neck (wood) stems

Used almost exclusively on wood furniture, grip neck stems have 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 and that’s the one you need. So stop right here, you are done.

20 Series Light-Duty Stem Casters

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 stems

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 and a ruler or tape measure.

1

An adjustable wrench is a handy tool to measure the diameter of the stem. Take the wrench and tighten it down gently across the stem. Be careful to not have the wire ring or brass band between the jaws of the wrench. We’re concerned with the diameter of the machined stem.

2

Once you have the wrench tightened down, use your ruler to measure the gap between the jaw. Measure inside to inside, the example illustration shows a 7/16″. Write down the diameter.

3

Measuring the length is a little simpler. Use your ruler to measure the length of the stem from the top of the flared base to the tip of the stem. The caster stem on the right is 7/8″ long. 

Threaded stems

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. 

1

Use the adjustable wrench to measure the outside diameter of the threaded caster stem. Make sure that you only have the thread between the jaws, none of the base. It’s best to position the wrench at the midpoint of the stem.

2

With the wrench gently tightened down, use your ruler or tape measure to measure the between-jaw distance. Read the measurement carefully, as threads are sold on 1/16″ increments. Now you have the thread diameter.

3

Measuring the length is a little simpler. Use your ruler to measure the length of the stem from the top of the hexagonal, flared based of the threaded stem. The caster stem on the right is 1″

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