Wheelchair Bearing Inside Diameter (ID) Measurement Tool

In the USA, a wheelchair can use a mix of both Imperial and Metric Bearings. So I wanted to create a simple tool that would allow anyone to measure the bearings on their wheelchair without having to own calipers.

There are two tools here, one flat and one round. They both work the same. There are 4 diameters staggered by smallest to largest. They are as follows 608 (8mm ID), R6 (3/8" ID), 6001 (12mm ID), and R8 (1/2" ID) in that order. If you insert the tool in the bearing and it it only