The structural forms of CNC machine tool tool holders are divided into two types: integral and modular. In the integral tool holder, the working part that clamps the tool and the shank part used for installation and positioning on the machine tool are integrated. This type of tool holder has poor adaptability to changes in machine tools and workpieces. To adapt to changes in workpieces and machine tools, users must stock various specifications of tool holders, resulting in low utilization rates of the tool holders. The modular tool system is a more advanced tool system, where each tool holder can be assembled from various serialized modules. Different assembly schemes can be adopted for different workpieces and machine tools, resulting in multiple tool holder series, thereby improving the adaptability and utilization rate of the tool holders.

The selection of the tool holder structure should consider both technical advancement and economic rationality: ① For some simple tools that are used repeatedly over the long term and do not require assembly, it is appropriate to equip them with integral tool holders, which offer good tool rigidity and are inexpensive (such as end mill holders for machining the outer contours of workpieces, collet chucks, and drill chucks). ② When machining multiple varieties and small batches of workpieces with frequently changing hole diameters and depths, it is advisable to choose modular tool holders to replace a large number of integral boring tool holders, thereby reducing machining costs. ③ For situations with multiple CNC machine tools, especially when the spindle ends and tool-changing robots of the machine tools are different, modular tool holders should be selected. Since the intermediate modules (extension rods) and working modules (tool-holding modules) used by each machine tool are universal, this can greatly reduce equipment investment and improve tool utilization.

Tool Holder Specifications

Most CNC tool holders adopt a 7:24 taper tool holder and use corresponding types of pull-stud tightening structures to match the machine tool spindle. Tool holders come in various specifications, with commonly used ones being No. 40, No. 45, and No. 50. Those widely used in China include ISO7388-1983, GB10944-1989, MAS403-1982, ANSI/ASME B5.50-1985, etc. When selecting, consideration should be given to the compatibility of the tool holder specifications with the machine tool spindle and the tool-changing robot.

Quantity of Tool Holder Specifications

The integral TSG tool system includes 20 types of tool holders, with the number of specifications reaching hundreds. Users can select the variety and specifications of tool holders based on the CNC machining process of the typical workpieces they process, which can meet machining requirements without causing overstock. Considering that a certain number of tool holders are being preset or have tools being reground while the CNC machine tool is working, the configured quantity of tool holders is usually 2 to 3 times the number of tool holders needed.

Matching of Tools and Tool Holders

Attention should be paid to the matching of tool holders and tools, especially when selecting tap holders, to ensure the size of the drive square of the matching tap. Additionally, selecting single-edge boring tools on CNC machine tools can avoid scratching the workpiece during retraction, but attention should be paid to the position direction of the tool tip relative to the keyway on the tool holder: some machine tools require it to be consistent with the keyway orientation, while others require it to be perpendicular to the keyway orientation.

Selection of High-Efficiency and Composite Tool Holders

To improve machining efficiency, high-efficiency tools and tool holders should be selected as much as possible. For example, for rough boring, a double-edge boring tool holder can be selected, which not only improves machining efficiency but also helps reduce cutting vibrations; selecting a powerful collet chuck can not only clamp straight-shank tools but also clamp tools with holes through extension rods. For typical workpieces with large batches and complex machining, composite tools should be selected as much as possible. Although composite tools and tool holders are relatively expensive, using composite tools for machining on machining centers can combine multiple processes into one process, completed by one tool, which helps reduce machining time and the number of tool changes, significantly improving production efficiency. For some special workpieces, specially designed composite tool holders can also be considered.