Max Knives MKRB6-9 — 9 mm ball bearing, 6 balls, folder pivot

Overview

The MKRB6-9 is a ball bearing sold individually, meant for rebuilding a folding knife or smoothing out its action. At 9 mm outer diameter it is the most compact of the four bearings in the series. Its 4 mm inner diameter and 4 mm thickness put it on smaller pivots, where space is tight. It weighs 1 gram and carries six balls.

Measure the recess before you order

A bearing is not chosen by eye. Too large for the recess machined in the liner, it will not seat, or it presses against the walls and locks the movement instead of freeing it. Too small, it floats in its seat and leaves play that the knife shows as a blade moving sideways. A caliper and three measurements taken on the stripped knife, outer diameter, inner diameter and thickness, are the step you cannot skip before ordering.

Technical specifications

Ball bearing, reference MKRB6-9, sold individually. Outer diameter 9 mm, inner diameter 4 mm, thickness 4 mm. Six balls. Weight 1 gram. A workshop part for rebuilding a folding knife or smoothing its opening action. It has the smallest outer diameter of the four bearings in the series, which also includes 10 mm and 12 mm models.

Care

A bearing runs clean or it does not run. Before fitting, dust and degrease the recess, then a drop of fine oil is enough to get the part going. After that it depends on use: a knife carried in a pocket picks up lint, an outdoor knife picks up sand, and in both cases the pivot is better rinsed and re-oiled than left to collect residue between the balls.