How to measure the stem size of a caster with a grip ring.
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Many people have difficulty accurately
measuring the grip ring stem ( mounting post ) on their chair or furniture
casters. The "grip ring" is the "C" shaped metal clip which compresses when
inserted in the holes in the bottom of the chair. It holds the caster in the
hole. If you want to replace a caster that has a "grip ring stem", first
try measuring with a ruler. Place the ruler perpendicular to the length of the
stem at the middle (not near the top or the ring). Most casters that have a
grip ring stem have 7/16" stem diameter. If the stem of your caster is 7/16"
diameter it will measure slightly less than the 1/2" mark on the ruler. The
only other grip ring stem diameter is 3/8". On a ruler, 3/8" appears half way
between the 1/4" and the 1/2" marks.
Second, you should double
check your effort by trying the following: |
Please
use both of our methods to measure the stem diameter.
Remember, measure
twice - order once.
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Cut a small piece of paper about 1/2" wide and about
2" long. These measurements are approximate. Start to wrap the paper around the
stem of your old caster as shown. |
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Wrap the paper so that it overlaps the beginning edge
of itself. Where the paper intersects the beginning edge, make a mark with a
pencil or pen. Try to make this mark as accurately as possible and make sure
that the paper is wrapped tightly around the stem. Now, let's take that
paper and use some geometry from high school. The diameter of a circle can be
found if you know the circumference of the circle. Well you just measured the
circumference by using your paper. Measure your paper from the beginning edge
to the mark that you made.
Using the formula d = circumference / Pi (
3.1416 )
We've done the math for you
below. |
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If you measured 1 3/8" - You
need 7/16" Diameter Stems.
If you
measured 1 3/16" - You need 3/8" Diameter Stems. |
| Now that you are sure of the stem
diameter, you need only one other dimension, namely, the depth of the hole. In
order for the replacement caster to work properly, the depth of the hole in the
chair must be equal to or greater than the length of the caster stem. An easy
way to measure the depth of the hole is with a pencil. Remove an old caster,
insert the pencil into the hole in the chair, mark the depth with your thumb;
remove and measure. |
Call us if your measurements are radically different than those
shown here. |
