How to choose a tool holder for machining center?

Precise machining center equipment with advanced cutting tools can provide excellent metal cutting productivity. As the key interface between the cutting tool and the spindle of the machine tool, the tool holder is essential for achieving high production. So, how do we choose, apply and maintain the tool holder that best suits the production needs?

1. Workpiece factors affect the selection of tool holders

　The main reason that affects the choice of tool holder lies in the machinability of the workpiece material in each operation and the configuration of the final part. These factors can determine the size of the tool holder required to reach a specific profile or feature. The handle should be as simple and easy to use as possible to reduce the possibility of operator error.

　The basic components of the machine tool play a key role: fast machine tools with linear guides will make full use of tool holders designed for high-speed applications, while machine tools with box grooves will provide support for heavy-duty machining. The multi-task machine tool can complete turning and milling/drilling processes at the same time, and the tool holder can also be selected according to the processing strategy. For example, in order to maximize productivity in high-speed cutting (HSC) processes or in high-performance cutting (HPC) applications, the shop will choose different tools. The former involves a shallower depth of cut HHS, and the latter focuses on power. Sufficient but limited speed machines produce higher metal removal rates.

　　The low repeatable radial runout helps to ensure a constant tool engagement, thereby reducing vibration and maximizing tool life. Balance is very important. High-quality tool holders should achieve precise dynamic balance under G2,5-25000 rpm mass (1 g.mm). The processing workshop can determine the tool holder system that can meet its production needs in a cost-effective manner according to the actual situation or consult the tool supplier.

　2.each tool holder should meet specific process requirements

　　 Whether it is a simple side-fixed type, a jacket type, a heat shrink type, a mechanical type, or a hydraulic type, the tool holder should meet the specific process requirements.

　　 collet chuck and interchangeable collet are the most commonly used round tool holder technology. The cost-effective ER type is available in various sizes and provides sufficient clamping force to achieve reliable light milling and drilling operations. The high-precision ER jacketed tool holder has low radial runout (< 5µm at the tool tip) and a symmetrical design that can be balanced for high-speed processes, while the reinforced type can be used for heavy-duty machining. ER tool holders are easy to change quickly and can be adapted to various tool diameters.

　　The thermal expansion tool holder can provide a strong clamping force, with a concentricity of 3 μm at 3xD, and a good dynamic balance quality. The small handle design can well reach the tricky part features.

　　The enhanced tool holder can be used for medium to heavy-duty milling, but the clamping force depends on the inner diameter tolerance of the tool holder and tool holder. Thermal expansion tools require the purchase of a special heating device, and the heating/cooling process requires more installation time than simply switching the jacket.

　　The mechanical milling chuck provides strong clamping force and high radial rigidity through multi-row needle roller bearings. This design can realize heavy-duty milling and fast tool change, but the runout may be greater than that of the jacket system. The size of the mechanical chuck is usually larger than other tool holder types, which may limit the tool's access to certain part features.

　　Compared with mechanical chucks, hydraulic chucks that use hydraulic pressure to generate clamping force have fewer internal components, so the appearance is relatively slim. The hydraulic chuck has low radial runout and can effectively carry out reaming, drilling and light milling at high spindle speeds, but it is sensitive to large radial loads.

　　 3. the spindle or tapered end determines the torque transmission capacity and tool centering accuracy

　　 is as important as how the tool holder fixes the cutting tool, it is how to install the tool holder on the spindle of the machine tool. Traditional BT, DIN, and CAT tool holder tapers are suitable for smaller machine tools, but may be limited in terms of high-speed machining. The model that is in double-sided contact with the tapered surface and end surface of the tool holder can provide higher rigidity and accuracy, especially in the case of large overhangs. Reliable transmission of larger torque requires a larger taper size. For example, the HSK-E32 tool holder cannot replace HSK-A125A in heavy-duty machining.

　　The choice of the taper form of the shank usually varies from region to region. In the mid-1990s, 5-axis machine tools became more and more popular, and it was during this period that HSK began to emerge in Germany. CAT tool holders are mainly used in the United States, while in Asia, BT tool holders are very popular and are often taper/end-face double-contact models.

　　HSK is often used for 5-axis machining. The connection between PSC (Polygonal Clamping System: Capto) and KM is mainly used for multi-task machine tools and adopts ISO standards. Both KM and Capto are modular systems that allow the combination of extension rods or reduced diameter rods to assemble tools of a specific length. As multi-tasking machine tools become more and more common, tool holders that can realize turning, milling, drilling and other processing types in a single clamping are becoming more and more popular.

　　 Therefore, the importance of the tool holder in the machining system is self-evident. How to correctly match the correct tool holder with a specific machine tool, processing strategy and workpiece is a key factor in increasing productivity and reducing costs.

　　Future technological improvements will no longer be limited to the handle itself. The use of software and RFID tags for tool management is an element of data-based manufacturing and will become more and more common in the future. Advances in toolholder technology include toolholders equipped with sensors that can monitor the force on the toolholder in real time. The collected data allows the operator to adjust the processing parameters during processing, and can even be adjusted automatically through artificial intelligence (AI) connected to the machine control unit. These technologies and other new technologies will further increase the production contribution value of the tool holder in the machining process.