JINING QINFENG MACHINERY HARDWARE CO.,LTD
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August 06, 2019

Various Tool Holders

Tool shank is a kind of tool, which connects the machine spindle with tools and other accessories. At present, the main standards are BT, SK, CAPTO, BBT, HSK and other specifications of spindle models
HSK tool system is a new type of high-speed short taper TOOL HOLDER. Its interface adopts the way of simultaneous positioning of the taper and the end face. The Tool Holder is hollow in the Hsk Tool Holder structure drawing. The taper length is short and the taper is 1/10, which is conducive to realizing the lightening and high-speed tool change. As shown in the figure below. Because of the hollow cone and end positioning, the radial deformation difference between the spindle hole and the tool holder is compensated, and the axial positioning error is completely eliminated, which makes high-speed and high-precision machining possible. This kind of tool holder is more and more widely used in high-speed machining centers.
Model structure diagram of HSK tool handle 6

Model structure diagram of HSK tool handle 6

KM tool holder
The structure of the tool holder is similar to that of HSK Tool Holder. The hollow short cone structure is also adopted with a taper of 1/10. The structure diagram of the conical KM tool holder and the way of simultaneous positioning and clamping of the end face are also adopted. As shown in Figure 1.3, the main difference is that the clamping mechanism used is different. The clamping structure of KM has been patented by the United States. It uses more clamping force and higher stiffness of the system. However, because there are two symmetrical arc grooves on the conical surface of KM tool shank (when used for clamping), it is thin in comparison, some parts have poor strength, and it requires a very large clamping force to work properly. In addition, the patent protection of KM tool holder structure limits the rapid popularization and application of the system.
Structure diagram of KM tool handle
Structure diagram of KM tool handle

NC5 tool handle
It also uses a hollow short cone structure with a taper of 1/10. It also uses both the cone and the end face to locate and clamp simultaneously. Because the torque is transmitted by the keyway on the cylinder at the front end of NC5 tool handle, and there is no keyway at the tail of tool handle to transfer the torque, the axial dimension of tool handle is shorter than that of HSK tool handle. The biggest difference between NC5 and the former two types of tool holders is that the tool holder does not have a thin-walled structure, and an intermediate taper sleeve is added to the conical surface of the tool holder. KM and HSK tool shanks compensate the manufacturing errors of the tool shank and spindle by the deformation of the thin wall, which ensures the reliable contact between the cone and the end face at the same time. NC5 tool shank achieves this goal by the axial movement of the middle cone sleeve. The axial moving power of the middle taper sleeve comes from the disc spring on the end face of the tool handle. Because of the strong error compensation ability of the middle taper sleeve, the NC5 tool holder has a slightly lower requirement for the manufacturing accuracy of the spindle and the tool holder itself. In addition, the NC5 tool holder has only one screw hole for installing pull screw. The hole wall is thicker and the strength is higher. The pressure-increasing clamping mechanism can be used to meet the requirements of heavy cutting. The main disadvantage of the tool holder is that a contact surface is added between the tool holder and the taper hole of the spindle, and the positioning accuracy and stiffness of the tool holder are reduced.
Structure diagram of NC5 tool handle
Structure diagram of NC5 tool handle
CAPTO Tool Handle
CAPTO handle. The structure of the tool handle is not conical, but triangular cone. Its edge is circular arc with a taper of 1/20. The hollow short cone structure uses both cone and end face to contact and locate. The triangular cone structure can realize the non-sliding torque transmission in both directions, eliminating the problem of dynamic balance caused by the transmission keys and keyways, and eliminating the need for transmission keys. The large surface of the triangular cone makes the surface pressure of the tool handle low, it is not easy to deform and wear small, so the accuracy is maintained well. However, the processing of triangular conical hole is difficult, the processing cost is high, and it is incompatible with the existing tool holder, and the matching will be self-locking.

BT High Speed Tool Handle
BT Cnc Tool Holder is mainly a Japanese standard, and it is also a commonly used standard. The universal tool handle with taper of 7:24 has five standards and specifications, namely NT (traditional type), DIN69871 (German standard), IS07388/1 (international standard), MASBT (Japanese standard) and ANSI/ASME (American standard).

The German standard of NT type tool holder is DIN2080, which is to tighten the tool holder by pulling rod on traditional machine tools, also known as ST in China; the other four kinds of tool holders are tightened by pulling nails at the end of the tool holder on the processing center. MASBT (BT) BT is a Japanese standard. Its installation size is totally different from DIN69871, IS07388/1 and ANSI. It can not be replaced.

The symmetrical structure of BT type tool holder makes it better than the other three kinds of tool holders in high speed stability. Titanium Hao is selected as the tool shank. The tool shank has 30, 35, 40, 45, 50 and 60 gauges, which indicate the diameter of the taper shank somewhere (the specific position is different in different standards). Cone specifications are usually chosen by machine tool manufacturers according to the effective power of the machine tool or the total length of the tool used. They are also related to the country of manufacture (DIN standard in Europe, ANSI standard in America and JIS standard in Japan). The commonly used specifications of tool shank are 30, 40, 50, of which 40 is the most widely used.
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