In the field of CNC machining, the toolholder pull stud, as a key component connecting the spindle and the tool, has a direct impact on the degree of standardization of machining accuracy and equipment compatibility. At present, the mainstream pull stud types on the market are mainly divided into Japanese, German and American three major standard systems, each type has its own unique structural characteristics and application scenarios.

1. Asian Standard System

BT Type pull stud (Japan JIS B6339 Standard)

As a standard set by the Japan Machine Tool Builders' Association (JMTBA), the BT type pull stud adopts a 7:24 taper design, which is notably characterized by a symmetrical double-plane structure at the end of the pull stud. This design suppresses vibration at high speeds (over 15,000 rpm) and is particularly suitable for precision cutting. It should be noted that although the BT type is similar in appearance to DIN 69871, there is an axial deviation of 0.5mm between the two due to key dimensional differences and mixing is strictly prohibited. Typical applications include Japanese machining centers such as Mazak and Okuma.

2. European standard system

HSK series pull stud (German DIN 69893 standard)

HSK hollow short taper shank system adopts revolutionary 1:10 taper + end face double contact design, its pull stud structure is different according to the type:

Type A: basic model, up to 40,000rpm

Type E: enhanced model, suitable for heavy cutting

Type F: economic model, used for general machining

The special feature is that HSK The special feature is that the HSK pull stud has a preload force of up to three times that of the BT type, which is particularly impressive in 5-axis machining. The representative manufacturers are DMG MORI, Hermle and other German machines.

NT/ST-type pull stud (German DIN 2080 standard)

As a typical configuration for conventional machine tools, the NT-type (known as ST-type in China) utilizes a unique direct fastening method for the pull stud. Its pull stud is actually a monolithic structure, which is connected to the drawbar through M12 internal thread. This design has a slower tool change speed (about 3 seconds/times), but has excellent load carrying capacity and is commonly used in heavy cutting equipment such as gantry milling machines.

3. the American standard system

CAT type pull stud (American ANSI B5.50 standard)

CAT standard most notable feature is to omit the wedge notch of the German shanks, this "subtractive design" to reduce its cost by about 15%. This “subtractive design” reduces the cost by about 15%. However, there is a compatibility issue to be aware of: CAT40 shanks cannot be fitted to BT40 spindles, whereas this can be achieved by means of an adapter. Typical users include American machine tool manufacturers such as Haas and Hurco.

4. Composite standard type

JT type pull stud (international standard)

As the type with the highest degree of standardization, JT type innovatively integrates the core elements of the three major standards:

adopts the accuracy requirements of DIN (radial runout ≤ 0.003mm)

retains the dimensional specifications of ANSI

is compatible with the MAS standard of the automatic tool changer

This "triple play" feature makes it the first choice of multinational enterprises for the selection of equipment, especially for machine shops with multi-national brands. This “three-in-one” feature makes it the first choice for multinational enterprises, especially suitable for machining shops with multi-national brands of machine tools.

5. Special function type

SK series pull stud (with safety module)

Three innovative designs have been added to the standard pull stud:

Manipulator slot: 45° beveled positioning slots are used to increase the accuracy of tool change by 30%

Mistake-proofing mechanism: Misassembly is prevented by asymmetric threads

Reinforcement of the bolt holes: 12.9-grade alloy steel bushings are adopted

Selection recommendations:

High-speed machining (>20,000rpm): Priority HSK-E63

Heavy cutting conditions: consider CAT50 or NT50

Multi-brand workshop: JT standard is recommended

Automated production line: recommend smart pull studs with RFID identification

As machine speeds continue to increase, pull stud technology also continues to evolve. The newly developed carbon fiber composite pull stud has begun trials in the aerospace field, with a 40% weight reduction and a threefold increase in fatigue life, which foreshadows the next generation of pull stud technology.

【 Go Back 】 | 【 Print 】