How should machining centers correctly select tool holders?

Precision machining centers, combined with advanced cutting tools, can provide excellent metal cutting productivity. As a crucial interface between cutting tools and machine tool spindles, the tool holder is crucial for achieving high productivity. So, how do we choose, apply, and maintain the most suitable tool holder for production needs?
01 Workpiece factors affecting tool holder selection
The factors that affect the selection of the tool holder include the machinability of the workpiece material in each operation and the configuration of the final part, which can determine the tool holder size required to achieve a specific profile or feature. The handle should be as simple and easy to use as possible to minimize the possibility of operator errors.
The basic components of machine tools play a crucial role - fast machine tools with linear guides will fully utilize tool holders designed for high-speed applications, while machine tools with box grooves provide support for heavy-duty machining. Multi task machine tools can simultaneously complete turning and milling/drilling processes.
You can also choose the tool holder according to the processing strategy. For example, in order to maximize productivity in high-speed cutting (HSC) processes or high-performance cutting (HPC) applications, workshops will choose different cutting tools. The former involves shallow cutting depth HHS, while the latter focuses on producing higher metal removal rates on machine tools with sufficient power but limited speed.
Lower repeatable radial runout helps to ensure a constant amount of tool engagement, thereby reducing vibration and maximizing tool life. Balance is crucial, and high-quality tool holders should achieve precise dynamic balance at G2,5-25000 rpm (1 g. mm). The processing workshop can determine the tool holder system that can meet its production needs in an economically efficient manner based on the actual situation or consult with the tool supplier.
02 Each type of handle should meet specific process requirements
Whether it is a simple side fixed type, jacket type, heat shrink type, mechanical type, or hydraulic type, the tool handle should meet specific process requirements.
Spring collets and interchangeable sleeves are the most commonly used circular tool holder techniques. Economically efficient ER provides various sizes and sufficient clamping force to achieve reliable light milling and drilling processes. The high-precision ER jacketed tool holder has low radial runout (<5 µ m 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. The ER tool holder is easy to quickly convert and can adapt to various tool diameters.
The thermal expansion tool handle can provide strong clamping force, with 3 at 3xD μ The concentricity of m and excellent dynamic balance mass. The compact handle design allows for easy access to tricky part features.
Enhanced tool holders can perform medium to heavy-duty milling, but the clamping force depends on the inner diameter tolerance of the tool holder and tool holder. Thermal expansion cutting tools require the purchase of special heating devices, 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 multiple rows of needle roller bearings. This design can achieve heavy-duty milling and fast tool changing, but the runout may be greater than that of the jacket system. The size of mechanical chucks is usually larger than other types of tool holders, which may limit the tool's ability to reach certain part features.
Compared to mechanical chucks, hydraulic chucks that use hydraulic pressure to generate clamping force have fewer internal components, resulting in a relatively slender appearance. The radial runout of the hydraulic chuck is relatively low, and it can effectively expand holes, drill holes, and perform light milling at high spindle speeds, but it is sensitive to large radial loads.
The 03 spindle or conical end determines the torque transmission capability and tool alignment accuracy
Equally important as how to fix the cutting tool with the tool holder is how to install the tool holder onto the machine tool spindle. Traditional BT, DIN, and CAT tool shank taper is suitable for smaller machine tools, but may be limited in high-speed machining. The models that come into contact with the taper and end face of the tool handle on both sides can provide higher rigidity and accuracy, especially in cases of large overhang. Reliable transmission of greater torque requires a larger taper size. For example, the HSK-E32 tool holder cannot replace HSK-A125A in heavy-duty machining.
The choice of taper form for the handle usually varies by region. In the mid-1990s, 5-axis machine tools became increasingly 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 often come in models with double-sided cone/end contact.
HSK is commonly used for 5-axis machining. The PSC (Polygonal Clamping System: Capto) and KM connections are mainly used for multitasking machine tools, using ISO standards. KM and Capto are both modular systems that allow for the assembly of specific lengths of tools by combining extension or reduction rods. With the increasing popularity of multitasking machine tools, tool holders that can achieve machining types such as turning, milling, and drilling in one clamping process are becoming more and more popular.
04 Summary
The machining workshop must attach importance to the importance of tool holders in the machining system and understand how to correctly match the correct tool holder with specific machine tools, machining strategies, and workpieces to improve productivity and reduce 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 essential element of data-driven manufacturing and is becoming increasingly common. The advancement of tool holder technology includes tool holders equipped with sensors, which can monitor the force on the tool holder in real-time. The collected data allows operators to adjust machining parameters during the machining process, and can even be automatically adjusted 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.