Collet

[1][2] One of the two radial surfaces of a collet is usually tapered (i.e a truncated cone) and the other is cylindrical.

Most often the collet is made of spring steel, with one or more kerf cuts along its length to allow it to expand and contract.

An external collet clamps against the internal surface or bore of a hollow cylinder.

While the clamping surface of a collet is normally cylindrical, it can be made to accept any defined shape.

The table below gives a functional comparison of the three most common types of chuck used for holding workpieces.

This gives the disadvantage of higher capital cost and makes them unsuitable for general usage in electric drills, etc.

Furthermore, it is not uncommon for machinists to make a custom collet to hold any unusual size or shape of part.

Thus a given collet holds any diameter ranging from its nominal size to its 1-mm-smaller collapsed size, and a full set of ER collets in nominal 1 mm steps fits any possible cylindrical diameter within the capacity of the series.

"Autolock" collet chucks (Osbourn "Pozi-Lock" is a similar system) were designed to provide secure clamping of milling cutters with only hand tightening.

Collets are only available in fixed sizes, imperial or metric, and the cutter shank must be an exact match.

For work holding, collets are sized in 0.1 mm increments with the number on the face being the diameter in tenths of a millimetre.

The book The Modern Watchmaker's Lathe and How to Use it[13] contains tables of makers and sizes; note that it refers to basic collets as split wire chucks.

These collets are common especially on production machines, particularly European lathes with lever or automated closers.

Unlike draw-in collets, they do not pull back to close, but are generally pushed forward, with the face remaining in place.

They can be used to hold strait-shanked tooling (drills and milling cutters) more securely and with better accuracy (less run-out) than a chuck.

On a wood router (a hand-held or table-mounted power tool used in woodworking), the collet is what holds the bit in place.

The collet nut is hexagonal on the outside so it can be tightened or loosened with a standard wrench, and has threads on the inside so it can be screwed onto the motor arbor.

Many users (hobbyists, graphic artists, architects, students, and others) may be familiar with collets as the part of an X-Acto or equivalent knife that holds the blade.

The two collet halves have an internal raised rib which locate into a circular groove near the top of each valve stem, the outer side of the collet halves are a taper fit into the spring retainer (also known as a collar), this taper locks the retainer in place and the raised rib that sits in the circular groove on the valve stem also locks the collet halves in place to the valve stem.

On reassembly it is difficult to keep the split collets in place whilst the compressor is released, by applying a small amount of grease to the internal side of the split collets will keep them in place on the valve stem whilst releasing the compressor, then as the spring retainer rises it locks the tapered split collets in place.

The Blaser R93 (and related models) use a unique bolt locking system that employs an expanding collet.

The collet has claw-like L-shaped segments that face outward from the axis of the barrel.