Contents

• Introduction to Collets
• What is a Collet?
• Types of Collets
• Collet Type Comparison Table
• Summary of Collets

Introduction to Collets

Collets are one of the most widely used toolholding and workholding tools in CNC machining, manual milling, turning and other precision manufacturing processes. Whether you're working on a lathe, mill, or grinder, selecting the right collet type can greatly influence your machining accuracy, tool life, and overall efficiency.

In this blog, we’ll explore and compare the most commonly used collet types in machining: ER, 5C, 16C, R8, SK, and DA. We’ll go over their features, uses, pros, cons, and help you choose the best collet type for your next project

What is a Collet?

A collet is a specialized workholding tool used to clamp and hold a workpiece, tool, or insert securely within a spindle or chuck. The collet’s spring mechanism allows it to expand and contract, gripping the workpiece tightly with minimal runout, ensuring accuracy and precision during machining operations.

Types of Collets

Let’s take a closer look at the most common types of collets and compare their features: 

1. ER Collets

Features:

•    Size Range: From 1mm to 26mm (depending on the specific ER series)

•    Applications: CNC milling, drilling, and precision turning

•    Collet Body: The ER collet has a cylindrical shape with a slotted body, designed to hold round shanks securely.

Advantages:

•    High Precision: Offers excellent runout accuracy, ensuring tight tolerances.

•    Versatility: Available in a wide range of sizes and can hold both round and square tools.

•    Common Use: The ER series is one of the most widely used collets, especially for toolholders and CNC machine setups.

Disadvantages:

•    Limited Clamping Force: Can struggle with holding tools in heavy-duty applications due to lower clamping force compared to other collet types.

2. 5C Collets

Features:

•    Size Range: 1/16” to 2-1/16”

•    Applications: Mainly used in lathe work, especially for holding round and hexagonal workpieces

•    Collet Body: Features a cylindrical shape with a flange, and it is designed to provide high clamping force on the workpiece..

Advantages:

•    High Clamping Force: Excellent for holding workpieces during turning operations, ensuring rigidity and stability.

•    Versatility: Can hold round, hexagonal, and square workpieces. Some models offer accessories for tapered parts.

•    Quick Setup: Fast and easy to load and unload, which improves productivity.

Disadvantages:

•    Limited to Specific Machines: Primarily used in lathes, making them less versatile in milling operations compared to ER collets.

3. 16C Collets

Features:

•    Size Range: 1/16” to 2”

•    Applications: Primarily used for lathe turning, though less common than 5C collets.

•    Collet Body: The 16C collet has a similar design to the 5C but offers a larger gripping area for greater holding power.

Advantages:

•    Increased Clamping Power: Provides better grip and control, especially for larger diameter parts.

•    Versatility: Suitable for holding a wide range of parts, from round to hexagonal workpieces.

Disadvantages:

•    Compatibility: Less commonly found than the 5C collet, meaning it’s not as widely supported across machines.

4. R8 Collets

Features:

•    Size Range: 1/8” to 7/8” (or larger)

•    Applications: Mainly used for milling operations on Bridgeport-style milling machines.

•    Collet Body: The R8 collet features a tapered design (R8 taper) and is secured via a drawbar for tight grip on the tool shank.

Advantages:

•    Widely Used in Milling: The R8 collet is especially designed for vertical milling machines, offering good accuracy and a broad size range.

•    Ease of Use: Quick to change out and compatible with many Bridgeport-style machines.

•    Affordable: R8 collets are often cost-effective compared to other collet types.

Disadvantages:

•    Limited to Specific Machines: Only compatible with milling machines that use the R8 spindle system.

•    Lower Precision: Compared to ER or 5C collets, the R8 typically provides lower clamping accuracy.

5. SK Collets

Features:

•    Size Range: Available in a variety of sizes depending on the SK (or SK-type chuck) specifications

•    Applications: CNC milling machines, primarily used in Europe

•    Collet Body: Features a tapered design similar to the CAT or BT systems, offering secure clamping.

Advantages:

•    High Precision: Known for excellent clamping accuracy, SK collets provide high precision in milling operations.

•    Compatible with a Range of Machines: Common in CNC machining centres, particularly in European machine shops.

Disadvantages:

•    Expensive: Compared to some other collet types, SK collets can be pricier, especially in terms of toolholder compatibility.

6. DA Collets

Features:

•    Size Range: Typically 1/8” to 1” in diameter

•    Applications: Primarily used in drilling, milling, and boring operations

•    Collet Body: The DA collet features a spring-loaded body designed for low-torque, high-precision operations.

Advantages:

•    Precision Holding: Designed for precise toolholding in applications like boring and drilling.

•    Great for Small Tools: Well-suited for holding smaller tools, making them ideal for fine finishing work.

Disadvantages:

•    Limited Range: Not as commonly available for large toolholding applications.

•    Low Clamping Force: Like the ER collet, it may not be ideal for heavy-duty cutting.

Collet Type Comparison Table

Summary of Collets

Each collet type has its specific advantages depending on the application, material, and machine compatibility. From the high clamping power of 5C collets to the versatility and precision of ER collets, choosing the right collet can ensure a smoother, more efficient machining process. 

For those looking for cost-effective solutions on CNC milling machines, R8 collets offer a great option, while SK collets are ideal for high-precision European machines. Whether you need quick-change capability or precision for small tooling, you now have the knowledge to make an informed decision. Please feel free to contact our expert in-house technical support team who can provide even more knowledge and expertise on 01924 869 615 or email sales@cutwel.net.