A ball bearing guide is a crucial part that works in conjunction with the cutting tip of a router to ensure precise, smooth cuts. This guide consists of a closed, wheel-like casing that attaches to a shank or bit-spindle on a router. The guide rolls along like a wheel and is placed in contact with a jig or edge surface to steady the movement of the router while cutting. It is essential for achieving even, smooth cut moldings and finishing.

Ball bearing guides come in various sizes that depend on the size of the cutting bit and the bearing’s location. Some bits have a small bearing located below the cutting tip to assist in cutting moldings or edges while acting as a horizontal “depth” gauge. When the ball bearing is above the cutting edge of the bit, it serves as a guide for deeper, multiple-pass cuts but can only be used once that depth has been reached. If the ball bearing guide does not rotate freely, it should be replaced immediately with the same size to ensure continued effectiveness.