CNC machining: the top things! You must understand!

What is a top?
Machine tool tops are machine tool parts used in machining. There are two types: rotary tops and fixed tops. Tops can support parts with complex end faces and parts that do not allow center holes. Tops are mainly composed of ejectors, clamping devices, housings, fixing pins, bearings, and mandrels.
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Application of tops
One end of the top can push the center hole or the inner hole of the tube, and the other end can push the parts with spherical or conical top faces. The top is fixed by a clamping device. When the part does not allow or cannot punch a center hole, the clamping device can be used to clamp and turn it directly. The housing and the mandrel are drilled with pin holes, and the fixing pins are inserted or removed to achieve the two uses of the top.
Top classification:
There are two types of lathe tops: front tops and rear tops. Lathes are used for centering and to bear the gravity and cutting force of the workpiece.
1) Front top of lathe The front top can be directly installed in the taper hole of the lathe spindle. The front top rotates with the workpiece without relative motion, so quenching is not required.
The lathe can sometimes use a three-jaw self-centering chuck to clamp a self-made steel front center with a 60° taper angle. In order to prevent the displacement of the center due to the axial force during turning, the clamping part of the chuck on the self-made center should be made into a step-type. When the lathe is removed from the chuck, if it is used again, the 60° taper surface must be re-turned.
2) The rear center There are two types of rear centers: fixed centers and rotary centers. When in use, the rear center can be inserted into the tapered hole of the lathe tailstock sleeve. The fixed center has good cutting properties and accurate centering, but there is sliding friction between the center hole and the hard tip, which is easy to wear and burn the center. Therefore, the lathe is only suitable for workpieces with high precision requirements for low-speed processing. When the lathe supports small workpieces, the reverse center can be used. At this time, the end of the workpiece is made into a center shape. The movable center is equipped with rolling bearings inside, and the center rotates with the workpiece, and can work normally at high speeds. However, the rigidity of the live center is poor, and sometimes it will cause vibration and reduce the processing accuracy. Therefore, the live center is only suitable for workpieces with low precision requirements.
Uses of the top
The top can also be used for drilling, threading and reaming of workpieces. A universal machine tool accessory top, which is connected to the housing by a three-jaw self-centering chuck or a four-jaw chuck through fasteners. A bearing is provided between the housing and the mandrel, and is embedded with a fixing pin. The feature is that one end of the top is a convex pointed cone and oblique spline, and the other end is a concave hemispherical and conical blind hole.
Features of the rotary top

№1 Small outer diameter, less interference knife, suitable for high speed and moderate cutting;

№2 Regular oiling can be used to extend the service life;

№3 It has a certain waterproof function and is easy to dissipate heat as a whole;

№4 It adopts an inclined long needle bearing, and the three-point support arrangement structure has enhanced rigidity and good stability. Fixed tops have cones and half-side heads.
Features of fixed top:
No.1 Standard front tungsten carbide top;
No.2 The material of tungsten carbide top is SK2, with a hardness of 75HRC±2;
No.3 Both the top and the body need to be precisely ground to meet the requirements.
There are many types of rotary tops. When using them, we choose different rotary tops according to the specific conditions. The wear resistance of the rotary top is very high, and there will be no damage when using the rotary top. The rotary top is often used in some large equipment. When using the rotary top, we pay attention to daily maintenance to ensure the normal operation of the machine.