All About Collets: Types and Sizes

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Even if you have never heard the name, you have probably come across or even used a collet once or twice. These small machining components may be simple, but they still perform a vital function in woodworking and metalworking.

Collets vary in size and design, so it is no surprise that some work better in certain applications than others. Choosing the right collet is essential for completing projects safely and efficiently. This article will define collets, explore the different varieties and discuss their best uses.

What is a Collet?

LLDSIMEX 65Mn Material 13Pc R8 Precision Round Spring Collet Set 1/8-7/8 x 1/16Ths

A collet is similar to a chuck, and many people erroneously use the terms interchangeably. While chucks can be tightened and loosened around an object, collets are flexible sleeves that hold an object with clamping pressure. 

Bits or other tools are inserted into the tapered end of the collet, which presses up against the item when fitted into the machine, fixing it in place. The tapered end has two or more narrow slits partially running down the shaft, giving it just enough flexibility to lock firmly onto the bit.

Because collets have no moving parts, they cannot be adjusted for different-sized bits. They are not ideal for all applications and can only hold one size. You may have to change out several collets just for one project.

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Collets do carry several benefits when you are shooting for accuracy and efficiency. Collets are reliable for precise self-centering and a strong clamp, making them both effective and resistant to loosening. And while changing out collets may seem tedious, their fast-chucking feature makes swapping them out relatively easy.

Collets are so accurate and easy-to-use that they are suitable for anyone from novices to skilled craftsmen. However, collets are designed individually for different uses, the most common being for woodworking and metalworking.

Collet Types for Woodworking and Metalworking

In woodworking, collets are used primarily for routers and drill presses to hold the bits. Collets in these settings rarely fit anything larger than a ½” bit. In routers, collets hold the cutting bit in place with a hexagonal nut, making it easier to fasten and loosen with a normal wrench. The tailend is often threaded on the inside to attach to the motor arbor.

Collet types and sizes are more varied in metalworking. In these applications, collets are commonly shaped for round bars or tools but can also be found in hexagonal, square or unique custom shapes. Step collets are also available when needing to work with larger bits, as they “step” up in size from the spindle. There are even some collets that can hold the workable piece from an interior surface, allowing for the exterior to be worked.

What Are ER Collets?

ER-16 Collet Set 12PCS ER-16 Spring Collet Set 1/32-3/8 CNC Super Precision 3/32 7/32 11/32

Developed in 1973, ER collets have emerged as the most versatile, reliable and widely-used collet type across several industries. The standard ER collet series consists of eight different sizes, ranging from E-8 to E-50. The number represents the diameter of the tapered end in millimeters.

ER collets have a broad range of applications, including milling, drilling, reaming, tapping and cutting. However, although they are the most commonly used collet type, ER collets only feature a spring geometry suitable for round bits. For square or hexagonal shapes, you will need to choose from other specialty collets.

What Makes ER Collets Special?

Despite only being available in a round shape, ER collets are the most accepted collet due to their versatility. While most collets can only fit exactly one size bit, the tapered end of ER bits can collapse to hold bits smaller than its nominal size.

The different bit sizes usable with a single collet carry a 0.5mm range for small bits, a 1mm range for mid-size bits and a 2mm range for larger bits. For example, an E-8 collet can hold bits between 7.5-8mm in diameter but an E-50 can hold bits between 48-50mm in size.

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With ER collets, users can do the same job with a smaller inventory, as they do not have to swap out collets as often. This saves considerable space, time and effort. Plus, ER collets are widely regarded for their user-friendliness, stronger clamping pressure and convenience in installing and removing.

What Does ER Stand for?

The ER designation refers to the particular design of the collet. The “E” is a relic of the original E collet. The E collet was similar to the ER collet, but lacked the ER collet’s external groove, which facilitates its removal from a machine’s spindle. The “R” comes from the clamp manufacturer Rego-Fix, who modified the E collet design to create the ER style we use today.

Having the right collet can make the difference in finishing a project with precision, especially if you are relatively new to woodworking and metalworking. For more information on choosing the right collets for your next project, contact our team of experts today.


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1 thought on “All About Collets: Types and Sizes”

  1. I have a wood lathe with a 3/4 inch x 16 threaded spindle. I wish to use a mandrel with a morse taper to turn pen barrels. I assume a an adaptor and a collet chuck is required. What can you suggest?

    Thank you,
    Dale Young


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