Collets - how do they work and what is important!

What exactly does a collet chuck do, and how do you choose the right collet for your machine and tool?

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What is a collet?

A collet chuck is a clamping device for quickly and force-locking workpieces or tools (drills, cutters, etc.) with high accuracy.

It consists of an outer cone-shaped, radially slotted sleeve with a defined round, sometimes square or hexagonal shape.

Collets clamp bare or machined parts quickly, firmly and precisely centrally. They are suitable for high speeds. Sealing collets allow coolant to be fed into the tool.

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How does it work?

A collet chuck includes a Collet holder with an inner cone that matches the collet. Tightening is carried out by tightening a screw nut with which the collet chuck into the inner cone of Collet holder is pressed.

As a result of the collet chuck being slotted, the interior of the hole is evenly compressed, as a result of which the workpiece or tool is held firmly in place. The clamping range of a collet chuck is very small, which means that collets with appropriate dimensions must be kept available for different diameters.

What is important?

In order to choose the right collet, we must first look at the name of the collet chuck.

Example: ER32 Ø10 - 9.

HE: Type

32: Size

Ø10 — 9: Clamping range

If possible, clamp the tool shaft over the entire length of the collet, but at least 2/3 of the collet chuck length

Never clamp excessively large shafts, e.g. tool shaft diameter 11 mm into a collet chuck Ø10 — 9 mm

Tools with a clamping surface (Weldon) must be the clamping surface in the collet chuck.

Make sure that the collet chuck has the appropriate concentricity (15µm, 5µm or 2µm) for the selected speed. The higher the speed, the lower the µ-value.

If the tool breaks directly on the collet, the collet should no longer be used. The collet chuck has received a blow or even has visible damage. This leads to runout inaccuracy and imbalance. This has a negative effect on the life of the tool and the processing quality.

Damaged collets cause premature tool breakage. Therefore, you should not use them.

Keep collets clean and rust-free

The collet chuck is a wear and tear item and should therefore be replaced regularly.

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