THE GIB

Definition

A gib is a metal shim inserted between two mechanical parts, one of which is generally movable relative to the other. Its function is to ensure a stable, play-free position of the movable part, while allowing this play to be precisely adjusted by means of a screw device.

Application to the lathe carriage and to the milling machine

In watchmaking, the gib notably equips the slides of the carriage of a lathe, as well as the guides of a milling machine. Inserted between the movable slide and the fixed guide that supports it, it compensates for wear and manufacturing tolerances which, without it, would generate lateral play detrimental to the precision of movements.

Operation

The gib is held in place by adjustment screws that allow it to be moved very slightly within its housing. By progressively tightening these screws, the operator reduces the play between the slide and its guideway until smooth guidance is achieved, without blocking movement. Correct adjustment of the gib directly determines the precision and repeatability of the machining operations carried out on the machine.

Good to know

The principle of the gib is not limited to carriages: it is also found between the steady rest (or spindle carrier) and the bed bar of a lathe, where it likewise ensures an invariable and adjustable position between these two components.