What does 7:24 in the BT tool handle mean? What are the standards of BT, NT, JT, IT and CAT? Nowadays, CNC machine tools are widely used in factories. These machine tools and the tools used come from all over the world, with different models and standards. Today I want to talk to you about the knowledge about machining center tool holders.
The tool holder is the connection between the machine tool and the tool. The tool holder is a key link that affects concentricity and dynamic balance. It must not be treated as an ordinary component. Concentricity can determine whether the cutting amount of each cutting edge part is uniform when the tool rotates once; dynamic imbalance will produce periodic vibrations when the spindle rotates.
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According to the spindle taper hole, it is divided into two categories:
According to the taper of the tool hole installed on the spindle of the machining center, it is usually divided into two categories:
SK universal tool holder with a taper of 7:24
HSK vacuum tool holder with a taper of 1:10
HSK vacuum tool holder with a taper of 1:10
SK universal tool holder with a taper of 7:24
7:24 means that the taper of the tool holder is 7:24, which is a separate taper positioning and the taper shank is longer. The cone surface plays two important roles at the same time, namely the precise positioning of the tool holder relative to the spindle and the clamping of the tool holder.
Advantages: It is not self-locking and can quickly load and unload tools; manufacturing the tool holder only requires processing the taper angle to high precision to ensure the accuracy of the connection, so the cost of the tool holder is relatively low.
Disadvantages: During high-speed rotation, the tapered hole at the front end of the spindle will expand. The amount of expansion increases with the increase of the rotation radius and rotation speed. The stiffness of the taper connection will decrease. Under the action of the pull rod tension, the axial displacement of the tool holder will occur. There will also be changes. The radial size of the tool holder will change every time the tool is changed, and there is a problem of unstable repeat positioning accuracy.
Universal tool holders with a taper of 7:24 usually come in five standards and specifications:
1. International standard IS0 7388/1 (referred to as IV or IT)
2. Japanese standard MAS BT (referred to as BT)
3. German standard DIN 2080 type (NT or ST for short)
4. American standard ANSI/ASME (CAT for short)
5. DIN 69871 type (referred to as JT, DIN, DAT or DV)
Tightening method: The NT type tool holder is tightened through a pull rod on a traditional machine tool, also known as ST in China; the other four tool holders are pulled on the machining center through a rivet at the end of the tool holder. tight.
Versatility: 1) Currently, the most commonly used tool holders in China are DIN 69871 type (JT) and Japanese MAS BT type tool holders; 2) DIN 69871 type tool holders can also be installed on machine tools with ANSI/ASME spindle taper holes; 3) The international standard IS0 7388/1 tool holder can also be installed on machine tools with DIN 69871 and ANSI/ASME spindle taper holes, so in terms of versatility, the IS0 7388/1 tool holder is the best.
HSK vacuum tool holder with a taper of 1:10
HSK vacuum tool holder relies on the elastic deformation of the tool holder. Not only does the 1:10 taper surface of the tool holder contact the 1:10 taper surface of the machine tool spindle hole, but the flange surface of the tool holder is also in close contact with the spindle surface. This double The surface contact system is superior to the 7:24 universal tool holder in terms of high-speed machining, connection rigidity and coincidence accuracy.
HSK vacuum tool holder can improve the rigidity and stability of the system and product accuracy during high-speed machining, and shorten the time of tool replacement. It plays an important role in high-speed machining and is suitable for machine tool spindle speeds up to 60,000 rpm. HSK tool systems are being widely used in manufacturing industries such as aerospace, automobiles, and precision molds.
HSK tool holders are available in various specifications such as A-type, B-type, C-type, D-type, E-type, F-type, etc. Among them, A-type, E-type and F-type are commonly used in machining centers (automatic tool changers).
The biggest difference between Type A and Type E:
1. Type A has a transmission groove but type E does not. Therefore, relatively speaking, type A has a larger transmission torque and can relatively perform some heavy cutting. The E-type transmits less torque and can only perform some light cutting.
2. In addition to the transmission groove, the A-type tool holder also has manual fixing holes, direction grooves, etc., so the balance is relatively poor. The E type does not have it, so the E type is more suitable for high-speed processing. The mechanisms of E-type and F-type are exactly the same. The difference between them is that the taper of the E-type and F-type tool holders (such as E63 and F63) with the same name is one size smaller. In other words, the flange diameters of E63 and F63 are both φ63, but the taper size of F63 is only the same as that of E50. Therefore, compared with E63, F63 will rotate faster (the spindle bearing is smaller).
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How to install the knife handle
Spring chuck tool holder
It is mainly used for clamping straight-shank cutting tools and tools such as drill bits, milling cutters, and taps. The elastic deformation of the circlip is 1mm, and the clamping range is 0.5~32mm in diameter.
Hydraulic chuck
A- Locking screw, use an Allen wrench to tighten the locking screw;
B- Lock the piston and press the hydraulic medium into the expansion chamber;
C- Expansion chamber, which is squeezed by the liquid to generate pressure;
D- Thin expansion bushing that centers and evenly envelops the tool clamping rod during the locking process.
E-Special seals ensure ideal sealing and long service life.
Heated tool holder
Induction heating technology is used to heat the tool clamping part of the tool holder so that its diameter will expand, and then the cold tool holder is placed into the hot tool holder. The heated tool holder has strong clamping force and good dynamic balance, and is suitable for high-speed machining. The repeated positioning accuracy is high, generally within 2 μm, and the radial runout is within 5 μm; it has good anti-fouling ability and good anti-interference ability during processing. However, each size of tool holder is only suitable for installing tools with one shank diameter, and a set of heating equipment is required.
Post time: Jan-25-2024