Operation and sharpening of milling cutters

Operations to sharpen the cutters support the technical and physical characteristics of parts, thereby prolonging their working life. There are many approaches to the implementation of such activities, the choice among which is determined by the nature of the operation and the design of the element. The intensity of wear of the cutter largely depends on its design, from which the master selects and maintenance modes.

For example, the selection of the method of re-sharpening of high-speed parts is guided by the wear of the front surface. On the other hand, the sharpening of mills on the back surface is more suitable for shaped elements. Therefore, it is important to take into account as many operational factors as possible that will allow you to make the right choice of processing techniques.

Varieties of milling cutters

Such elements are widely used in the processing of parts on copy, kalevochno-tenore, milling and other machines. As a rule, this woodworking equipment, although there are also details for working with metal billets. The cutters are different in size, shape and purpose.

In general, there are two categories of elements - terminal and packed. The first differ in the presence of a shank, which is fixed in a special niche of the spindle. Products of the second group have a central hole that allows them to be pushed onto the working spindle and securely fixed. Accordingly, such sharpening of mills is characterized by a higher level of quality, not to mention the convenience in handling parts for the operator. Nasadnye elements can be compound, integral and prefabricated.

A feature of this group is the possibility of forming a cutting tool from several milling parts. Also worth noting is the category of end milling cutters, which can be combined and integral. The elements are divided into the quality of the foreded processing. So, sharpening of mills with flattened surfaces is made on the front face in order to maintain the basic angular parameters.

Maintenance of milling cutters

Despite the use of high-strength alloys in the manufacture of mills, a long time of operation leads to erasure, as well as deformation of the faces. Over time, worn out items are recycled, but before the expiration of the work resource the master can restore the characteristics of the part with the help of maintenance activities. It is important to take into account that sharpening of milling cutters allows not only to provide them with the same geometry, which ensures high-quality work. This procedure also increases the durability of the element, reducing the consumption of the tool. But this does not mean that any milling cutter can be restored in this way.

Technologists do not recommend bringing the tool to the state of complete wear and tear. Manufacturers of mills indicate in the marking technical and operational values, which are limiting for a particular element, and after their overcoming, the cutting edges are not amenable to restoration.

Technical support of the grinding process

For grinding, special milling machines are used, equipped with spindles with a rotational speed of up to 24,000 rpm on average. Before you start working on them, the master performs the balancing of the cutters. It can be implemented in two ways - dynamic and static. In the first case, the procedure is performed on a special machine, which not only balances the force, but also the torque acting on the milling cutter during rotation. This technique is especially important for cases when the milling cutter for metal is being milled.

The machines for balancing according to the static method assume only the balancing of the force acting on the milling cutter. The element is fixed in the frame, after which it is balanced through a device consisting of two horizontal guide knives. Directly sharpening is performed on special high-precision equipment.

Machines are available in different configurations, assuming both manual and automatic control. Common for all units of this type is the presence of linear bearings on the guide surfaces of the working surface. This structural solution makes it possible to achieve high accuracy of moving the element, as a rule, with an error of 0.005 mm.

equipment requirements

To ensure high-quality sharpening of cutters, you should not just use the equipment suitable for this task, but also properly prepare it. First of all, the spindles of the equipment must have sufficient vibration resistance, rotate freely and have minimum run-out values. Further, the feeding mechanism should work stably in all directions provided by the design without delays and with minimal gaps. Of great importance are the settings of the angle of rise - in this parameter there must also be high accuracy. For example, sharpening a worm cutter, which is performed on automatic machines, involves the installation of a certain angle of elevation, and the pitch of the screw groove. If grinding wheels are used, it is important to ensure a reliable fit of the interchangeable washers and spindles, due to which the working element is precisely positioned.

Machining of end milling cutters

The processing of end elements is most often done manually on universal grinding equipment. Typically, this technique updates the performance of the tool with a screw tooth. In many respects, the sharpening of the end mills resembles a similar renewal of cylindrical mills by means of a cup wheel. This applies to operations that involve the installation of an end mill in the center of the seat. Similar grinding is performed on semi-automatic models. In this case, end mills with a diameter of 14 to 50 mm can be serviced. The processing is suitable for both the rear and the front surface.

Sharpening of face milling cutters

Cutters made of high-speed steel, as well as some elements equipped with carbide-tipped plates, are sharpened in assembled form. The main back surface of the face cutter is ground with a grinding cup circle. Before performing the same operation on the plane of the auxiliary back side, the element is first set so that its cutting edge is positioned horizontally. After that, the axis of the milling cutter rotates horizontally and at the same time tilts in a vertical plane. In contrast to the scheme by which the end mills are sharpened, in this case the position of the workpiece is changed several times. Work with the front surface of the tooth can be carried out by the end part of the grinding disc circle or by the disk circle from the peripheral side.

Work with disk milling cutters

On the back of the main surface, the disk elements are machined with a cup. The auxiliary rear surface is made by analogy with the end mills, that is, by reversing the cutting edges horizontally. At the same time, the processing of the end teeth of such a tool is noted. In this case, the sharpening of the disk milling cutters is performed on the front surface in such a way that the machined teeth are directed upward. At the same time, the cutter itself should occupy a vertical position. The slope of the vertical axis of the element should correspond to the position of the main cutting edge.

Features of sharpening of milling cutters on wood

The end fittings are sharpened without special tools, usually with a thin diamond bar. This element either lies on the edge of the desktop, or, if the cutter has a deep notch, is fixed by an additional tool. The cutter is inserted through the fixed bar. During processing, the bar is periodically wetted with water. When the procedure is completed, the wizard thoroughly cleans and dries the product. As the front surfaces are grinded, the edge becomes sharper, but the diameter of the tool decreases. If the cutter has a guide bearing, it must first be removed, and then continue the operation. The fact is that sharpening the milling cutter along a tree together with a damaged bearing can lead to spoilage of the element. It is also necessary to clean the instrument of the residues of wood tar with a special solvent.

Features of sharpening of milling cutters for metal

Such elements are less common and at the same time require less effort in the preparation process. Processing is performed using grinding wheels of suitable grain size. Materials in this case can be different, in particular, the use of diamond wheels, as well as parts made of conventional or white electrocorundum, is common. If it is planned to sharpen the end mills for metal made from tool steel, then it is recommended to choose electrocorundum disks. For products with higher characteristics it is desirable to use elborovye circles. The most productive and effective sharpening parts are made of silicon carbide. They are used to handle tools made from hard alloys. Before work, the abrasive is cooled, as high temperature loads during the operation can adversely affect the structure of the circle.

Machining of toothed milling cutters

Seamed elements are used in those cases where it is required to increase the stability of the cutting part and reduce the surface roughness. The teeth of the forested cutter are machined on the front surface in such a way that, after recoiling in the radial section, the profile of the functional edge retains its original parameters until the part is fully used. Sharpening of such cutters is also carried out with a strictly fixed front corner. In the case of sharp-edged elements, a constant angle of sharpening must be observed.

Finishing of milling cutters

In effect, this is an operation designed to correct the result obtained during the main grinding process. Typically, the debugging is carried out in order to ensure optimum roughness indicators or in those cases when it is necessary to adjust the angle of sharpening of the milling cutter with the working faces. Quite common techniques are abrasive and diamond debugging. In the first case, it is assumed that fine-grained circles of silicon carbide are used, and in the second case diamond discs are used on a bakelite bond. Both techniques allow you to cope, among other things, with a hard-alloy tool.

Quality control of sharpening

During the inspection, the master evaluates the geometric characteristics of the cutting surfaces for compliance with technical requirements. In particular, the milling beat is determined, as well as the degree of roughness of the finished or ground planes. In the control of parameters directly on the workplace, auxiliary devices can be used. For example, if the end cutter was sharpened on wood material, the specialist can measure the angles along the working faces. For this, a goniometer is used, in which the scale is represented in the form of an arc. Special measuring tools are used to evaluate other parameters, again, most of them are oriented to checking the geometrical data of the cutter.

Conclusion

The need for machining of the cutting tool is preserved even in the age of high technology. The only change in this respect occurred with the control systems of milling equipment. There are automatic devices that allow to optimize the process of handling blanks. However, sharpening of drills, cutters, bits and other machining metal elements is still carried out using abrasives. Of course, there are alternative technologies that allow restoring the geometry of the details, but they are not yet widely spread. This applies to laser technology, hydrodynamic machines, as well as installations that have a thermal impact. At this stage of their development, for economic reasons, many enterprises still prefer traditional methods of sharpening.