STEP 1 Measuring the Bearing Bore (Inner Diameter / ID)
The bearing bore size is the measurement of the hole in the center of the bearing.
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Best method: Use a vernier caliper for the most accurate result.
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Steps:
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Insert the outer anvils of the caliper into the bearing’s bore.
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Open the caliper slowly until it fits snugly but not tightly against the inner ring.
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Read the measurement on the caliper scale in millimeters or inches.
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Pro tip: If a vernier caliper is not available, a high-quality steel ruler can be used for approximate measurements.
STEP 2 Measuring the Outside Diameter (OD)
The outside diameter is the total width across the bearing from one outer edge to the other.
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Place the jaws of the caliper around the outer ring of the bearing.
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Close the jaws gently until they make contact without compressing the bearing.
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Record the measurement in mm or inches.
This dimension is critical when fitting the bearing into a housing or casing.
STEP 3 Measuring the Bearing Width (W)
The width refers to the thickness of the bearing.
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Position the caliper jaws on both sides of the bearing’s faces.
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Close until snug, ensuring no extra pressure is applied.
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Read the value to determine the exact width.
Why Accurate Bearing Measurement Matters
Choosing the correct bearing dimensions ensures:
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Proper fit in mechanical assemblies
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Longer service life and reduced wear
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Smooth rotation and minimal vibration
For precise results, always use a vernier caliper and measure at least twice to confirm accuracy. This is especially important for miniature bearings and micro-sized bearings where tolerances are very tight.
