Dunham Expanding Collets:

5C, 16C, 3J Systems:

Lathes, Grinders, Special Machines:

 (Special Collet Sizes Available)

Dunham Tool's Expanding Collets are designed for holding workpieces on their inside diameters for a variety of operations on Lathes, Cylindrical Grinders, Polishing Machines and many Special Machining, Laser Joining and Assembly Machines.  Please see below for Dunham CAD Layout and Assembly Drawings detailing the complete range of Dunham 5C, 16C and 3J Expanding Collets. 

Dunham Collets are designed for use with all standard 5C, 16C and 3J Collet Chucks, Spindles, etc.  

Dunham 3J Expanding Collet

By design, Dunham Expanding Collets are a 'true length' or 'dead length' workholding tool because the Collet's male taper remains fixed on the Collet Chuck's female taper which permits exceptionally accurate and repeatable control of the workpiece location.

We manufacture Dunham Expanding Collets in 29 standard sizes to accomodate workpiece diameters ranging from 1/4" to 6" and workpiece lengths up to 3".  Dunham Collets are designed to be 'finish machined' by the end user on their machine(s), assuring that the Dunham Expanding Collet is optimally matched (TIR) for maximum concentricity relative to the end user's spindle.  While 'finish machining' by the end user yields maximum accuracies (and cost savings), Dunham will also machine the collet to the customer's specifications.

Dunham Expanding Collets were originally designed in 1958 by our founder, Russell Dunham, and we were awarded a patent to his design in 1959.

Dunham Expanding Collet Size Chart

Dunham Expanding Collet Assembly Drawing

Straight Shank Mandrels

Dunham Expanding Collets are one of a wide range of Dunham workholding and spindle devices: 50M Spindle Headstocks, Cartridge Spindles, Collet Chucks, Collet and Chuck Actuators and Cylinders, machineable Expanding Mandrels, Bar Pulling Systems, as well as 5C, 16C and 3J 'Plug and Play' Collet Chucking Systems for all Lathes, Rotary Tables, Grinding Mahcines and Special Machines, Thru Hole and No Thru Hole Kits available: