A collet fixture is a workholding device that uses a tapered collet to grip round, hexagonal, or square stock securely and concentrically for turning, milling, or grinding operations. Unlike a three-jaw chuck, which grips at three discrete points, a collet closes evenly around the entire circumference of the workpiece, delivering higher gripping accuracy and repeatability with minimal runout. Buyohlic supplies collet fixtures for lathe and milling applications used by machinists, toolmakers, and production shops throughout the USA who need dependable, low-runout workholding.
How Collet Fixtures Work
A collet fixture consists of a body that houses a slotted, tapered collet and a closing mechanism, typically a draw tube, closer nut, or lever action, that pulls the collet into a matching taper. As the collet is drawn inward, its slots compress evenly around the workpiece, creating uniform clamping pressure along the full length of contact rather than at isolated points.
Because the clamping force is distributed evenly, collet fixtures typically achieve significantly lower runout than jaw-type chucks, which is why they are the preferred choice for precision turning, second operations, and any job where concentricity between features matters.
Common Collet Systems
- ER collets, widely used on milling machines and tool holders, available in ER8 through ER50 sizes
- 5C collets, common on lathes and collet fixtures for round, hex, and square stock
- R8 collets, standard on many manual milling machine spindles
- Dead-length collets, which hold the workpiece at a fixed length regardless of clamping pressure
Common Applications
- Second-operation turning, where a part must be re-chucked with minimal runout
- Precision milling of round or hexagonal stock
- Production runs requiring fast, repeatable part changes
- Toolholding for end mills, drills, and reamers in milling applications
Choosing the Right Collet Fixture
Start by identifying the collet system your machine or tool holder is already built around, since collets are not interchangeable across systems. From there, consider the size range of stock you typically run; a shop working primarily with small-diameter round stock may only need a handful of ER collet sizes, while a shop running mixed round, hex, and square material will benefit from a 5C fixture with a broader accessory range. If your work also involves indexed rotary operations, a collet fixture can often be paired with a rotary table setup for combined centering and indexing accuracy.
