How to sharpen a cutter for metal 11.09.2017 21:16
The industry produces a huge number of cutters for metal and their sharpening for those who work with them is often a problem. Design features tool and a large number of teeth makes sharpening difficult.
How to sharpen a cutter for metal?
As a rule, sharpening of a cutter for metal is carried out on special equipment. Incorrect sharpening leads to tooth breakage and cutter failure. Correct sharpening milling cutters allows you to use the tool much longer in work and reduce wear. Also, for this, it is necessary to carefully monitor the cutting surface of the teeth of the cutter.
For sharpening cutters for metal, special machines and special equipment are used. Therefore, it is better to entrust this matter to professionals.
The peculiarity of sharpening cutters is the relatively large length and curvilinearity of the cutting edges of their teeth. When sharpening, it is required to ensure that the surface of the circle moves exactly along the edge.
What are the cutters
- Cylindrical milling cutters are used for processing workpieces using machines equipped with a horizontal spindle.
- End mills - for milling workpieces on machines with a vertical spindle.
- End mills - for driving ledges, recesses, contours (curvilinear). Are used on installations at vertical milling processing.
- Disc cutters - for driving grooves, grooves on horizontal machines.
- Key cutters - for grooving on machines with a vertical spindle.
- Angle cutters - for milling planes (inclined), grooves, bevels.
- Shaped cutters - when processing shaped surfaces.
In the metalworking industry, the use of milling cutters as cutting tool has a wide distribution. Almost all parts of various engines, both electric and internal combustion, are manufactured using milling. Lots of details for household appliances, machines and fixtures are also processed using cutters.
The cutter is a type of round rotary cutter. It always has a circle in its cross section, and the shape itself can be any, including very complex ones. Along the circumference are furrows (there are different depths) or teeth. They process the material during the rotation of the cutter. is a complex and painstaking process. It is important that not only the specialist has a certain level of skill, but also the sharpening tool meets the highest requirements. Otherwise, chips, cracks or unsharpened areas will remain on the cutter after processing, which will directly affect the further execution of milling work.
Varieties
Incisors are the most different types- end, end, disk, slotted, cylindrical, slot. And this is not all varieties. They are also divided according to their purpose and are angular, shaped, keyed, for T-shaped grooves. Another division - according to the type of surface to be treated:
- for metal;
- on wood;
- on plastic;
- on glass;
- and others.
Sharpening cutters for metal complicated by a large length of the cutting surface. Such work is possible only with the use of special tools. In some cases, you have to grind by hand, but for this you need to have a lot of experience. Otherwise, all previous work will go down the drain. Notches, notches, chips and cracks will appear on the grooves (teeth). The part will have to be re-grinded, which invariably reduces its size.
Today, a fairly large number of cutters of various sizes are produced. They can be classified according to functional and constructive qualities.
Sharpening of end mills is carried out using special devices for such tools. In some cases, sharpening can be done manually.
Milling cutters have relatively great length and uneven teeth for cutting. In the process of sharpening, you will need to take care of the movement of the base of the circle along the edge. In this case, it will be necessary to sharpen the shaped cutters that have a backed corner. You should know that sharpening is quite difficult. To preserve the profile of the structure and facilitate the sharpening process, the backed teeth will need to be sharpened exclusively along the front base. Sharp teeth, which have a flat or curved shape, must be sharpened exclusively along the back base. Slotting and parting cutters can be sharpened on the front and back bases of the teeth.
Tooth geometry
The geometry of the teeth of the cutter: a - sharpened tooth, b - backed tooth.
To sharpen correctly, you need to know the geometry of the teeth of the cutter. According to the design of the teeth, cutters with backed and sharp teeth are distinguished. In the latter, the part of the rear base, which is adjacent to the cutting edge, is a plane. Teeth with sharp ends in most cases are sharpened along the back base, but they can also be sharpened along the front base of the tooth.
The backed teeth, which come with end mills, have a back base made in the Archimedes spiral. It is quite difficult to process a shaped base technologically, therefore it is possible to sharpen cutters with backed teeth only along the front base.
Regardless of the number of teeth in the cutter, each of them can be considered as a separate tooth, which is characterized by typical parameters for a tooth - the angles of the front and back, the size of the grinding area, and the angle of the teeth.
The sharpening platform is an element of the back base of the tooth, which is subjected to grinding during sharpening along the back base. On this basis, the maximum wear of the teeth will occur. Its size affects the magnitude of the friction force between the tool and the workpiece, so the base must be maintained in a specific range.
The scheme of sharpening prefabricated cutters on a universal grinding machine.
The basic rake angle is the angle between the tangent to the front base and the base of the axis. It can be measured in a plane that will pass through a given point perpendicular to the main cutting edge.
Primary clearance angle is the angle between the tangent to the flank at a given point on the primary cutting edge and the tangent to the plane of rotation at that point. This angle helps to reduce friction between the tool and the workpiece.
With the help of the auxiliary rear angle, it is possible to characterize a large gap between the milled base and the body of the clove. It is necessary to sharpen the tool along an additional angle with a specific amount of damage to the tool and an increase in the area for sharpening. Target this action is to reduce the friction between the tooth and the workpiece to be milled. You should be aware that not all tools of this type have this angle.
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How to sharpen end mills for woodworking?
The shape of the teeth can be straight or helical. The inclination of the tool teeth can be described as the angle between the developed edge screw type and the axial part of the tool.
The values of the tooth angles will depend on the type of tool, the grade of alloy and steel from which it is made, as well as the type of material for which the tool is intended to be milled.
When milling viscous materials, the main rake angle should be selected in the range of 15-20° or more. Hard metal tools for milling steel will have an angle of 0° or -5°. The rear angle varies over a wide range.
Items you will need:
- Diamond beam.
- Table.
- Water or soapy solution.
- Solvent.
- abrasive paper.
- plank from hard rock wood or steel strip.
- abrasive circle.
It is possible to sharpen shaped end mills without special devices for sharpening, along the front base, with a diamond bar of small thickness. The beam must be installed on the extreme part of the table. If the tool has a large recess, then the tool must be fixed along the table.
Heat resistance table various materials, °C.
When sharpening, the timber will need to be moistened clean water or soapy solution. After sharpening, the tool will need to be washed and dried.
In the process of sharpening the front base, the edge will become sharper, but the diameter of the tool will decrease slightly.
If a bearing is installed on the tool, then the first step is to dismantle it, and then sharpen it. Trying to save time in this case may end up with a damaged bearing and a broken cutter.
Be sure to clean the cutter from excess resin from trees. For this, it is best to use a solvent.
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In the process of sharpening tools, it will be necessary to use bars of different grain sizes. The grit will depend on the thickness of the removed layer of material and the desired cleanliness of the base. Before sharpening, you will need to make sure that the timber has the right shape.
Figure 1. Grinding wheel shapes.
If the cutter teeth are made of relatively soft material, instead of a beam, you can use abrasive paper, which is glued to a flat base. As a base, you can use a plank of hardwood or a steel strip.
End mills for wood milling are sharpened for special device with low rotation speed. In this case, you will need to use a suitable abrasive wheel.
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Sharpening wheels
Sharpening of modular cutters can be done with circles of white or ordinary electrocorundum, diamond and others. For example, using electrocorundum wheels, you can qualitatively sharpen cutters for working with metal and wood, which are made of tool or other standard steel. Elbor wheels have the ability to sharpen steel structures high performance. Silicon carbide and diamond wheels are used for sharpening hard metal cutters.
By increasing the temperature, the hardness of such a device decreases. A temperature of 1000°C can reduce the hardness by almost 2 times. At a temperature of 1300 ° C, this indicator will decrease by about 6 times.
Figure 2. Sharpening of the end mill: a - the main cutting edge, b - the auxiliary cutting edge, c - installation diagram of the cutter for sharpening the teeth of the auxiliary cutting edge.
The use of water to reduce the temperature in most cases leads to rust on the workpieces and corners of the machine. To eliminate corrosion, soap and some electrolytes must be added to the water, which can form films for protection. When grinding, a solution with soap or soda is almost always used. If fine grinding is performed, then a low-concentration emulsion should be used.
In order to increase the quality of grinding with an abrasive wheel and reduce significant damage, it is recommended to select the maximum grit that can provide the necessary cleanliness class of the base of the used cutter.
The circumferential speed of the wheel during sharpening of hard metal teeth should be approximately 15-18 m/s. For example, in the process of using a circle with a diameter of 12.5 cm, the engine speed should be approximately 1600-2700 rpm. If it is necessary to sharpen more brittle materials, the operations must be performed at a lower speed. When using hard metal tools, the use of a hard mode leads to high stresses and cracks, and in some cases damage to the cutting edges. Wheel wear in this case will increase.
Wheel shape for sharpening the rear corner of the teeth on the base cylindrical shape should be cup or plate. To sharpen the front corner, you need to use a disc-shaped or flat-shaped circle.
The existing forms of grinding wheels can be seen in (Fig. 1).
The cutter can work productively only under the condition correct operation. If the work is carried out with correctly assigned milling modes, the cutter can process a large number of workpieces before it becomes noticeably dull. However, if you continue to work with a noticeably dull cutter, the cutting force will increase dramatically, which will cause an increase in friction, rapid further dulling and even breakage of the teeth of the cutter.
Sharpening a normally dull cutter requires relatively little time and does not significantly reduce the size of the tooth. Sharpening a very blunt cutter is a long, laborious operation, you have to remove a fairly large layer of metal, so the cutter does not need to be brought to severe bluntness.
It is especially necessary to monitor the condition of the cutting edges and timely sharpening of expensive cutters made of high-speed steel and equipped with carbide inserts.
Sharpening cylindrical cutters with pointed teeth
Cylindrical cutters with pointed teeth are sharpened along the back surface of the tooth with a cup circle (Fig. 332), while maintaining a predetermined rear angle.
When sharpening, the cutter is put on a mandrel installed in the centers of the grinding machine. The axis of the cup circle is set at an angle of 1 - 2 ° to the axis of the cutter, so that the circle touches the cutter being sharpened with only one side (Fig. 332, c).
If the axes of the cup circle and the cutter being sharpened are located in the same horizontal plane (Fig. 332, a), then the rear angle α at the cutter's tooth will not work. To form a rear angle, the cup circle is placed below the axis of the cutter being sharpened by an amount H(Fig. 332, b), which is determined from a right triangle with side and angle α:
Angle α should be selected according to Table. 35.
The position of the cutter tooth during sharpening is fixed with a special stop (Fig. 332) in the form of an ordinary spring steel bar. The stop that supports the tooth being sharpened should be set very close to the cutting edge. It also serves as a guide when sharpening cutters with helical teeth.
When sharpening the back surface of cylindrical cutters with disk circles, a concave chamfer is obtained on the tooth, which weakens the tooth blade and accelerates their wear. Cup wheels when sharpening give a flat chamfer (ribbon), which ensures greater durability of the cutters; for this reason, sharpening cutters with disc wheels is not recommended.
End mill sharpening
sharpening main cutting edge the tooth of the face cutters is made along the back surface, similar to the sharpening of cylindrical cutters with pointed teeth (Fig. 333, a).
At sharpening the secondary cutting edge tooth (Fig. 333, b), first, the cutter is set so that its auxiliary cutting edge is in a horizontal position. Then the axis of the cutter is rotated in the horizontal plane by the value of the auxiliary angle in terms of φ 1 and at the same time tilted in vertical plane to the end rear angle α 1 . The sharpening of the front surface on the auxiliary cutting edge is carried out by the side surface of the cup wheel. The cutter is installed so that the secondary cutting edge is facing upwards, and the cutter axis is tilted in a vertical plane by the value of the front angle of the secondary cutting edge.
Sharpening end mills
main cutting edge end mills (Fig. 334) is made similarly cylindrical cutters the end surface of the cup circle when installing the end mill in the centers.
Sharpening the back surface on secondary cutting edge it is made like end mills with a cup circle. The cutter is fixed with a tapered shank in the socket of the cartridge.
Sharpening of disk cutters
Sharpening the back surface on cylindrical edge disk cutters are produced like cylindrical cutters with a cup circle.
The sharpening of the rear surface of the end teeth is carried out similarly to the sharpening of the teeth of the auxiliary cutting edge of the end mills. The sharpening of the front surface of the end teeth is carried out similarly to end mills. The teeth to be sharpened are directed upwards, and the cutter axis occupies the position:
a) vertical - when the cutter has simple teeth,
b) inclined - when the cutter has multidirectional teeth, and the angle of inclination of the axis of the cutter in the vertical plane is equal to the angle ω of the inclination of the cylindrical cutting edge.
Sharpening cutters with backed teeth
The teeth of the cutters are sharpened along the front surface. On fig. 335, and a diagram of the installation for sharpening a tooth with a rake angle γ equal to zero (radial front surface) is given, and in fig. 335, b - with a front angle γ greater than zero. Value H 1 shift grinding wheel from the center of the cutter is determined by the formula:
The amount of layer removed during sharpening for all teeth must be the same in order to avoid runout of the cutter. If one tooth has a smaller layer removed than the others, it will be longer, will remove chips of a larger section and will become dull sooner. Sharpening of milling cutters on the front surface is carried out with a disk-shaped circle.
When sharpening, make sure that the front surface is radial, as shown in fig. 336, a (tooth 3
). If the front surface has an undercut (tooth 1
) or, conversely, a negative rake angle (tooth 2
), the tooth profile will be distorted and will cut the wrong contour in the workpiece. The position of the cutter tooth during sharpening is fixed with a stop, which should be adjacent to the back surface of the tooth being sharpened.
So that after sharpening the cutting edges have minimal runout, it is recommended to sharpen using a copier that has the same number of teeth as the cutter being sharpened (Fig. 336, b).
Sharpening prefabricated cutters (milling heads)
The cutter blade has more sharpening elements. In addition to the rear corners, it is necessary to sharpen: the main corners of the corner edge in the plan φ and the transitional edge φ 0, the auxiliary angle in the plan φ 1 and the section of the transitional edge f 0 . To ensure sharpening of each corner in the plan, the cutter takes a position corresponding to this angle (Fig. 337). Sharpening can be done on special grinding or universal grinding machines.
When sharpening to special machines milling cutter 1 is inserted using its shank or a put on mandrel into the head 2 in a horizontal position (Fig. 338). Head 2 can be rotated about the vertical axis. The cutter can be rotated around its axis using the handwheel 3 and is fixed in the desired position with the help of a stop. After sharpening one tooth, a transition is made to the next by turning the cutter around its axis.
On fig. 339 shows the position when sharpening the cutter on a special grinding machine. First, the ends of the plates or knives are compared (I), then the plates are aligned along the cylindrical edges (II). To form rear corners, the head with the grinding wheel is tilted and fixed in this position (III); to obtain plan angles, the head with the cutter rotates about the vertical axis (IV, V, VI). The complexity of such sharpening is high and ranges from 3 to 12 hours, depending on the degree of blunting (removal value), the number of teeth and the diameter of the cutter.
It should be noted that the wear of the grinding wheel during sharpening by the machine mechanism is not compensated. Therefore, from sharpening one element of the first tooth to sharpening the element of the same name of the last tooth, a known wear of the grinding wheel accumulates. To eliminate the runout of the elements of the teeth that occurs during the wear of the grinding wheel, it is necessary to introduce an additional finishing pass, which increases the complexity of the operation.
On a universal grinding machine the cutter is sharpened in the centers (see Fig. 337). Due to the fact that the mounting holes, i.e., the mounting bases of the cutter, are not used in this installation, the error in the alignment of the sharpening of the cutter cutters increases.
Since prefabricated cutters are the main tool for high-speed cutting methods, the laboriousness of sharpening cutters could be a serious brake on the introduction of high-speed milling. Therefore, in the process of mastering high-speed milling, the sharpening process was redesigned in order to reduce its labor intensity. For this, a method was developed, tested and implemented for sharpening prefabricated cutters with dismantled cutters and plates and their subsequent installation using a template.
Before sharpening, insert knives are removed from the body and usually sharpened as a set. On fig. 340 shows a special rotary device for this purpose, which sharply reduces the complexity of sharpening. The device is installed in the centers of the universal grinding machine. After sharpening one element, the fixture with a fixed set of teeth is rotated to a predetermined angle and the other element is sharpened.
After sharpening is completed, the cutters are installed in the head body using different kind templates (Fig. 341, a - e). Checking the collected milling head beating should be done with an indicator template (Fig. 341, e).
Finishing of carbide cutters
When sharpening with a grinding wheel, the carbide plate heats up unevenly, as a result of which tiny cracks may appear on its surface. Cracks in the process of cutting increase and can be the cause of chipping of the tooth during operation.
One of the goals of finishing is the removal of a defective layer with cracks. The second task of finishing is to increase the surface cleanliness of the cutting edge, which is necessary to reduce friction and wear of the tooth, as well as (increase the purity of the machined surface. The third task of finishing is to eliminate blockages on the surface of the cutter teeth and give them a more correct geometry.
Finishing of cutting surfaces is carried out on special finishing machines with cast-iron disks or manually with a weak pressure of a cast-iron whetstone. Best Results finishing are obtained at the speed of the finishing disk in the range of 1.0-1.5 m/s. For finishing, boron carbide paste with a grain size of 170 - 230 is used.
When manually finishing, it is necessary to observe correct position whetstone in relation to the cutting edge and the correct movement of the whetstone. First, the front and rear surfaces are brought, then finishing (edging) chamfers are formed: for this, the plane of the touchstone is set at an angle of 45 ° to the front surface, and several passes along the cutting edge are made with a low pressure touchstone. It takes 2-3 seconds to form a bordering chamfer. for every knife.
Boron carbide is a strong abrasive. With a cast iron whetstone with boron carbide paste, wear holes can be removed on the teeth without removing the cutter from the machine, which is very important when high-speed milling small workpieces with short cutting periods.
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We sharpen:
- incisors
- dolbyakov
Correctly performed tool sharpening reduces its consumption and, accordingly, increases its resource. Therefore, it is necessary to carefully monitor the condition of the cutting edges and perform timely sharpening of the tool, avoiding excessive wear and, moreover, its breakage.
Sharpening and manufacturing of worm cutters
The production complex of the Spetsstanmash plant offers a full range of services for the manufacture and repair of metal parts and structures, including: the production and sharpening of milling cutters for metal, wood, cast iron, aluminum, graphite or plastic.
The milling cutter is an important tool in industry and workshops. Represents a detail of various shapes, with distinctive feature sharp teeth. Its main function is the mechanical processing of the harvested material.
The principle of operation of milling is the translational rotational movement of the teeth of the cutter.
Depending on the type of tool used, the result is obtained:
- small grooves or grooves when using end mills;
- milling large surfaces;
- baguette cutting, window frames, gear, etc. by means of spiral cutters,
- cutting with a disk cutter (plinth, panel, clapboard lining, wall beam, etc.).
An important characteristic of the cutter is the material of its manufacture, in particular the cutting part. These can be teeth made of high-speed steel, mineral-ceramic, cermet or diamond.
Diamond cutters are considered the most durable due to natural physical characteristics. But, they are the most expensive. All other materials become dull after some time during operation, especially if they are not used correctly. Purchasing new tools is expensive, but our skilled craftsmen and high-precision modern equipment allow the quality to perform such a type of repair as sharpening knives for cutters of any geometry:
- sharpening worm cutters
- sharpening of disk cutters
- crown cutters and other types.
Professional work on sharpening cutters increases the durability of the part, and significantly reduces the consumption of cutting teeth.
Sharpening worm cutters: from 600 rubles / PC. (depending on wear)
Minimum sharpening time: from 10 working days
Minimum order amount: 3500 rub.
* The exact cost can be found using the form or by phone
