Different Types of Machine Tool Shanks and Standards: Taper Shank & Hollow Taper Shank

Tool shanks are mainly divided into 7:24 taper shanks and 1:10 hollow taper shanks according to the interface form between the tool and spindle.

7:24 Taper Shank

7:24 refers to the taper of the shank being 7/24, which is positioned for a single cone, and the tapered handle is longer. The cone surface plays two important roles, the accurate positioning of the tool handle relative to the spindle and the clamping of the tool handle.

Advantages:

It is not self-locking and can realize rapid tool loading and unloading. As long as the taper angle is processed to high precision, the manufacturing tool handle can ensure the connection precision, so the cost of the tool handle is relatively low.

Disadvantages:

When the spindle rotates at high speed, the taper hole at the front end of the spindle will expand. The amount of expansion will increase with the increase of the rotation radius and speed. The taper connection stiffness will decrease. Under the pull of the pull rod, the axial displacement of the tool handle will also change. After each tool change, the radial size of the tool holder will change, and there is a problem of unstable repetitive positioning accuracy.

Types & Standards

7: 24 Taper shanks can be divided into the following types according to different standards:

– NT (DIN 2080) shank: no manipulator clamping slot, no error proofing function, with cylindrical tail, with the tension bolt hole. In the traditional machine tool, the tool handle is tightened by the pull rod, and other tool handles are tightened by the pull pin at the end of the tool handle on the machining center.

– BT (MAS 403 JIS B 6339) shank: with manipulator clamping groove, no error proofing function, with pulling bolt hole and internal cooling hole. The BT type is a Japanese standard, and its installation size is completely different from DIN 69871, IS0 7388/1, and ANSI, so it cannot be replaced. The symmetrical structure of the BT-type tool handle makes it better than the other three tool handles in high-speed stability.

– SK (DIN 69871) shank: with manipulator clamping slot, error proofing function, pull bolt hole, and internal cooling hole. There are two types of DIN 69871, namely DIN 69871 A/AD type and DIN 69871 B type. The former is internally cooled in the center, and the latter is internally cooled in the flange plate. Other dimensions are the same.

– JT (IS0 7388/1) shank: A new standard was issued in 2007, which integrates DIN69871-1:1995, ANSI/ASME B5.50-1994, and MAS 403 JIS B 6339, and includes all 7:24 taper shanks commonly used.

– CAT (ANSI/ASME B5.50-1985) shank: ANSI B5.50 is an American standard, and its installation size is similar to that of DIN 69871 and IS0 7388/1. However, due to the lack of a wedge notch, ANSI B5.50 tool handles cannot be installed on DIN69871 and IS0 7388/1 machine tools, but DIN 69871 and IS0 7388/1 tool handles can be installed on ANSI B5.50 machine tools.

1: 10 Hollow Taper Shank

The HSK hollow taper shank has a taper of 10:1, it relies on the elastic deformation of the tool handle, which not only makes the 1:10 taper of the shank contact with the 1:10 taper of the machine tool spindle hole but also makes the flange face of the tool handle close contact with the spindle face. This double-sided contact system is superior to the 7:24 universal tool handle in high-speed machining, connection rigidity, and coincidence accuracy.

HSK hollow taper shank can improve the rigidity and stability of the system and the product accuracy in high-speed machining, and shorten the tool replacement time. It plays a very important role in high-speed machining. It is suitable for the spindle speed of the machine tool to reach 60000 RPM. HSK tool system is widely used in aerospace, automotive, precision mold, and other manufacturing industries.

The German standard for HSK hollow taper shank is DIN 69893. There are six standards and specifications, namely, HSK-A, HSK-B, HSK-C, HSK-D, HSK-E, and HSK-F. There are three commonly used types: HSK-A (automatic tool change with internal cooling), HSK-C (manual tool change with internal cooling), and HSK-E (automatic tool change with internal cooling, high-speed type).