The precision of milling tool holding can be compared to that of measuring tools. Therefore, it is crucial to pay attention to and understand the correct use of milling tool holders to ensure accurate milling on the machine. There are generally five methods for holding milling tools: Weldon side lock, chuck & collet, hydraulic type, screw type, and heat-shrinking.
Methods 1#: Weldon Side Lock
This method offers extremely high clamping force and is often used in heavy-duty cutting applications and traditional machining or rough cutting on conventional machines. However, it has the drawback of low clamping precision and significantly high run-out tolerance, making it unsuitable for precision machining or high-speed milling.
Methods 2#: Chuck & Collet
This is the most commonly used method for holding milling tools. It allows for easy interchangeability by changing the collet, making it a cost-effective choice. However, due to its design, it has relatively low clamping force and is not suitable for heavy-duty cutting. The run-out tolerance after clamping is better than Weldon side lock but still has an error of around 0.02mm due to the quality of the collet.
Methods 3#: Hydraulic Type
This method utilizes pressurized fluid to hold the milling tool, creating a uniform and tight connection due to the fluid’s flow characteristics. As a result, it provides high clamping force and minimal run-out tolerance (within 0.01mm). However, it is relatively expensive and has a complex structure, and its hydraulic system needs careful handling to avoid damage.
Methods 4#: Screw Type
The screw type secures the milling tool and tool holder using locking screws. Users can change the type and size of the milling tool by adjusting the screw size. As it relies on locking screws, the clamping is extremely stable, making it suitable for rough machining. Its run-out tolerance is comparable to chuck & collet, making it suitable for precision machining as well.
Methods 5#: Heat-Shrinking
Heat-shrinking utilizes the principle of thermal expansion and contraction to tightly combine the milling tool and tool holder. During use, the tool holder’s clamping part is heated to expand, allowing the milling tool to be inserted. After cooling and contracting, the milling tool is firmly fixed. This method provides extremely high clamping force, enhancing overall rigidity, and achieves run-out tolerance as low as 0.005mm. It is ideal for both rough and precision machining.
Two Important Tips
- Run-Out Tolerance:
The precision of milling tool life is greatly influenced by the holding method, and run-out tolerance is one of the crucial factors. For carbide milling tools, every 0.01mm of error causes a 10% reduction in tool life. - Tool Holder Interference:
To prevent tool holder interference, the milling tool’s extension length (L) should be less than five times its diameter (D). If L>5D, the cutting forces may affect the tool, causing run-out. Heat-shrinking tool holders can minimize interference while maintaining rigidity.
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