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The Ultimate Guide to Choosing the Perfect CNC Spindle Gripper

What is a CNC spindle gripper?

The CNC spindle gripper, also known as the spindle pull stud or spindle tool holder, is a crucial component in CNC machines used for clamping and positioning tools. Its primary function is to ensure the tool is securely and accurately fixed to the spindle during the machining process through the control of the tool holder, and to enable quick tool changes during machining. The working principle of the spindle pull claw involves multiple complex mechanisms and precise control to ensure the smooth operation of the machining process.

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How does a spindle gripper work?

The spindle pull claw incorporates the following functional mechanisms to control the stable machining process of the tool:

  1. Clamping Mechanism: The clamping mechanism of the spindle pull claw typically uses disc springs or cylindrical springs. Through the compression and release of these springs, the tool is clamped and unclamped. The force and travel of the springs need to be precisely controlled to ensure stable clamping and safe release of the tool.

  2. Positioning Mechanism: To ensure accurate tool positioning on the spindle, the spindle pull claw is usually equipped with multiple positioning pins. These positioning pins accurately locate the positioning holes on the tool holder during the rotation of the pull claw, achieving precise tool positioning.

  3. Drive Mechanism: The drive mechanism of the spindle pull claw typically uses hydraulic or pneumatic methods. When the tool needs to be clamped or released, the drive mechanism moves the pull claw. The hydraulic or pneumatic system provides sufficient driving force while ensuring quick and accurate actions.

  4. Sensing and Control System: For precise control, the spindle pull claw is usually equipped with sensors and a control system. The sensors detect the position and status of the pull claw in real time, and the control system precisely controls the actions of the pull claw based on the sensor feedback.

  5. Automatic Tool Changer System: In automated machining, the spindle pull claw needs to work in conjunction with an automatic tool changer system. The automatic tool changer system can automatically identify the tools that need to be changed during machining and control the pull claw to complete the quick tool change.

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How to choose a CNC spindle gripper?

When selecting a spindle pull claw, it is often necessary to replace the existing pull claw without changing the machine spindle. To choose the appropriate spindle pull claw, consider the commonly used tool holder models, the machine brand, and the pull claw brand. This ensures compatibility and optimal performance.

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CNC Tool Holders and Pull Stud types

CNC spindle grippers are used to secure tool holders in the spindle of a CNC machine. The type of tool holder and pull stud determines the appropriate CNC gripper clamping system. Tool holders can be categorized based on national standards. Here is an overview of how tool holders are categorized according to different standards:

Categories of Tool Holders Based on National Standards

1. ISO (International Organization for Standardization)

•  ISO 7388-1: Specifies the dimensions for 7/24 taper tool holders, commonly known as CAT and BT.

•  ISO 7388-2: Covers the specifications for hollow taper shank (HSK) tool holders.

2. ANSI (American National Standards Institute)

• ANSI B5.50: Defines the standards for 7/24 taper tool holders, similar to the ISO 7388-1 standard. CAT tool holders fall under this standard.

3. JIS (Japanese Industrial Standards)

• JIS B 6339: Specifies the dimensions and requirements for 7/24 taper tool holders, such as BT tool holders.

• JIS B 6336: Covers the specifications for hollow taper shank (HSK) tool holders, similar to ISO standards.

4. DIN (Deutsches Institut für Normung)

• DIN 69871: Defines the dimensions for 7/24 taper tool holders used in milling machines.

• DIN 69893: Specifies the standards for HSK tool holders.

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Common Types of Tool Holders

1. CAT (V-Flange) Tool Holders

• Standardized under ANSI B5.50 and ISO 7388-1.

• Common sizes: CAT30, CAT40, CAT50.

2. BT (Big Taper) Tool Holders

• Standardized under JIS B 6339.

• Common sizes: BT30, BT40, BT50.

3. HSK (Hollow Shank Taper) Tool Holders

• Standardized under ISO 7388-2, JIS B 6336, and DIN 69893.

Common types: HSK-A, HSK-C, HSK-E, HSK-F.

4. ISO (7/24 Taper) Tool Holders

• Standardized under ISO 7388-1.

• Similar to CAT and BT tool holders but used in various international applications.

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You can see some examples of different types of CNC pull stud grippers at RicoCNC:

• ISO standard CNC gripper

CAT40 standard tool holder gripper: 850412-00052 CAT40 Gripper

CAT50 standard CNC gripper: Spindle Clamping Gripper BP50CAT

BT30 standard pull stud gripper

BT40 standard CNC bar puller gripper

BT50 CNC tool gripper 

HSK 63A drawbar gripper 

DIN30 CNC gripper

DIN40 CNC spindle grippers

DIN50 robot grippers

CNC Machine Brands

When selecting pull studs for your machine, always consult the procurement and replacement manual provided by the machine manufacturer. This ensures you choose the correct pull stud designed for your specific machine model, guaranteeing optimal performance and safety.

Such as Machine brands Makino, Mazak, Ortlieb, Hyundai Wia, Daewoo, Taqqun, Jingqin, Mori Seiki (DMG MORI), Okuma, etc.

CNC grippers brands

These manufacturers provide a wide range of pull studs and clamping systems designed to meet the rigorous demands of CNC machining. When selecting pull studs, it is crucial to choose products from reputable manufacturers to ensure compatibility, precision, and durability in your machining operations.

Such as BERG, OTT-JACOB, ACROW, ROYAL, TALONS, Chumpower, Bright, ROEHM, SMARTC, Doosan, Riken Seiki, etc.

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Determining the Right CNC Pull Claw Clamping System

The model of the CNC spindle gripper clamping system is determined by the specific tool holder and pull stud being used. Here’s a step-by-step guide to choosing the right clamping system:

1. Identify the Tool Holder Standard: Determine whether your tool holder is CAT, BT, HSK, or another type based on the relevant national standard.

2. Match the Pull Stud: Ensure the pull stud (retention knob) is compatible with the tool holder and machine spindle. Pull studs vary based on the taper size and thread specifications.

3. Consult Manufacturer Specifications: Refer to the CNC machine manufacturer’s procurement and replacement manual to verify the compatible pull stud clamping system.

4. Send the images of your CNC grippers: Rico can check the model if you have detailed images of the CNC spindle grippers, such as full sizes, and full sides images, if have model numbers on the grippers, it will be helpful.

5. Confirm the grippers brands: normally there will be the logo on the grippers.

Based on the information provided above, RicoCNC can select the right gripper for you!

Rico CNC is a one-stop shop of CNC tool holders, CNC spindle grippers, CNC router bits, CNC woodworking machine parts, Automation parts, Linear Motion systems, etc. You can contact us for more information. 

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