What does 7:24 in the BT holder mean?
What are the standards for BT, NT, JT, IT, and CAT?
CNC machine tools are now widely used in factories. These machines and tools come from all over the world and come in different models and standards. Talk to everyone today about the machining center tool holder.
The shank is the connection between the machine tool and the tool. The shank is a key link that affects the concentricity and dynamic balance. You should never treat it as a general part. The concentricity determines whether the cutting amount of each cutting edge portion is uniform when the tool rotates one revolution; the dynamic unbalance will produce periodic vibration when the spindle rotates.
1 according to the spindle cone hole divided into two categories
The taper of the tool hole according to the machining center spindle is usually divided into two categories:
SK universal shank with a taper of 7:24
HSK vacuum shank with a taper of 1:10
SK SK universal shank with a taper of 7:24
7:24 means that the taper of the shank is 7:24, which is a separate cone positioning, and the taper shank is longer. The cone surface also plays two important roles at the same time, namely the precise positioning of the shank relative to the spindle and the clamping of the shank.
ŸAdvantages: It can realize fast loading and unloading of tools without self-locking; the manufacturing of the tool holder can ensure the accuracy of the connection by processing the taper angle to high precision, so the cost of the tool holder is relatively low.
Disadvantages: At the high speed rotation, the taper hole at the front end of the spindle will expand. The amount of expansion increases with the increase of the radius of rotation and the rotation speed. The stiffness of the taper connection will decrease. Under the action of the tension of the tie rod, the axial displacement of the shank There will also be changes. The radial dimension of the shank changes after each tool change, and there is a problem that the repeat positioning accuracy is unstable.
Universal shanks with a 7:24 taper typically have five standards and specifications:
1. International Standard IS0 7388/1 (referred to as IV or IT)
2. Japanese Standard MAS BT (BT for short)
3. German standard DIN 2080 (referred to as NT or ST)
4. American Standard ANSI/ASME (CAT)
5. DIN 69871 (JT, DIN, DAT or DV for short)
Tightening method:
The NT type shank is used to tighten the shank by a tie rod on a conventional machine tool. It is also called ST in China. The other four shanks are used to tighten the shank on the machining center through the shank of the shank
Generality:
1) At present, the most used in the country are the DIN 69871 (ie JT) and Japan MAS BT type handles;
2) The shank of the DIN 69871 can also be mounted on a machine with an ANSI/ASME spindle taper;
3) The international standard IS0 7388/1 tool holder can also be mounted on the DIN 69871, ANSI/ASME spindle taper machine, so the ISO 7038/1 tool holder is the most versatile.
HS HSK vacuum shank with a taper of 1:10
The HSK vacuum shank is elastically deformed by the shank, not only the 1:10 taper surface of the shank is in contact with the 1:10 taper surface of the machine tool spindle hole, but also the flange surface of the shank is in close contact with the main shaft surface. The surface contact system is superior to the 7:24 universal tool holder for high speed machining, joint rigidity and coincidence accuracy.
HSK vacuum shank can improve the rigidity and stability of the system and the precision of the product during high-speed machining, and shorten the tool replacement time. It plays an important role in high-speed machining, and it adapts to the spindle speed of the machine to 60,000 rpm. HSK tool systems are being widely used in aerospace, automotive, precision mold and other manufacturing industries.
HSK holders are available in A, B, C, D, E, and F types, among which A, E, and F are commonly used in machining centers (automatic tool change).
The biggest difference between type A and type E:
1. Type A has a transmission slot and E does not. Therefore, the A-type transmission torque is relatively large, and relatively heavy cutting can be performed. The E-type transmission torque is relatively small, and only some light cutting can be performed.
2. In addition to the transmission groove, the A-type holder has manual fixing holes, direction grooves, etc., so the balance is relatively poor. The E type is not available, so the E type is more suitable for high speed machining. The E-type and F-type mechanisms are identical. The difference is that the E-type and F-type shanks (such as E63 and F63) are also called, and the taper of the F-type shank is smaller. That is to say, the flange diameters of E63 and F63 are both φ63, but the taper size of F63 is only the same as that of E50. So compared to the E63, the F63 will spin faster (small spindle bearings).
2 shank loading form
spring collet handle
It is mainly used for the clamping of straight shank tools and tools such as drills, milling cutters and taps. The elastic deformation of the circlip is 1mm, and the clamping range is 0.5~32mm.
Hydraulic chuck
A- locking screw, use an Allen key to tighten the locking screw;
B- lock the piston and press the hydraulic medium into the expansion chamber;
C- expansion chamber, compressed by liquid to generate pressure;
D- Thin expansion bushing that positions and evenly envelops the center of the tool holder during locking.
E- Special seals ensure an ideal seal and long service life.
Heating the handle
Inductive heating is used to heat the tool holder on the shank so that its diameter expands and the cold shank is placed in the hot shank. The heating shank has large clamping force and good dynamic balance, which is suitable for high speed machining. The repeating positioning accuracy is high, generally within 2μm, and the radial runout is within 5μm; the anti-fouling ability is good, and the anti-interference ability is good in processing. However, each type of tool holder is only suitable for a tool with a shank diameter and a heating device is required.
About the author