Two points for attention in selecting HSK tool holder material

DIN standard only specifies the geometry of HSK toolholder, but not the material used. Therefore, almost all of the HSK toolholders produced by tool suppliers refer to the traditional 7:24 taper shank. The "hollow" of HSK hollow short taper shank itself shows a potential problem: the axial section is very small, which is obviously the weak link of HSK hollow short taper shank.

The traditional toolholder is usually made of alloy steel, and then surface hardening or surface treatment is used to obtain a hard and wear-resistant surface and a tough core (hrc32-36). These heat treatment processes (such as carburizing and ion nitriding, hardness can reach HRC58-62, about 1 mm deep) are very suitable for 7:24 taper shank, and the price is not expensive. Because it has enough cross section, it is not easy to deform. According to the guidelines accepted by industry, this relatively stable matrix perfectly integrates the two properties - a soft and tough core, which can prevent the hard surface from cracking and falling off due to deformation, and a very wear-resistant and hard surface.

In some parts of HSK toolholder, it is very sensitive to large tensile stress. There are 30 ° The clamping surface, the contact surface between the keyway and the spindle during torque transmission, and the position of the radial through hole closer to the bottom of the keyway and the bottom of the empty tool slot. In fact, it is difficult to find these changes without microscope and special detection means. A toolholder seems to work normally. Once it is overloaded, stress concentration occurs at the crack position, and fracture is likely to occur when it reaches the critical value. This kind of brittle fracture may occur at any time during use.

Therefore, it is impossible to achieve higher toughness, higher wear resistance and corrosion resistance at the same time, but also low cost. We can't change the geometry of the product, it's standard. We are also constrained by the cost of mass production, and it is impossible to use expensive "space materials and technologies". In order to make this new interface with many advantages widely used in production, we have to constantly explore.

Therefore, the manufacturer and the user must choose the material of the handle. One is high strength, toughness and moderate wear resistance; The other is high wear resistance and medium strength.

The results show that the cross section of HSK spindle mounting hole with greater stress should have larger cross section area, and the material sensitive to stress concentration should not be used as much as possible. But it must be able to adapt to high-speed machining, that is, the weight should be light, and the radial deformation should be small under the action of centrifugal force.

Another important reason is the price of HSK spindle. Because the HSK spindle can't be repaired, because regrinding the taper will make the taper diameter out of tolerance and affect the pressing position of the clamping mechanism. Because of its high precision requirements and the use of milling cutters with large length diameter ratio to process the internal driving key, its price is very expensive. In order to prolong the service life of the spindle, it is suggested that the toolholder should be made of the same material. It is suggested that the small yield strength should be 14000kg / cm2 and the tensile strength should be 15400kg / cm2. Moreover, the hardness of the TOOL HOLDER (average HRC50) should be reduced, which is 6-8 degrees lower than that of the spindle, so as to protect the expensive spindle. In this way, the hardness of the Tool Holder's stressed surface is reduced, and the manufacturing cycle is shortened and the cost is reduced.