How are end mills sharpened? Sharpening and making hob cutters How to sharpen a slot cutter
Sharpening cutters is the final operation to obtain the specified geometric parameters, as well as to restore cutting properties lost as a result of tooth wear.
Correctly performed sharpening increases the durability of the cutter, and therefore reduces consumption. cutting tool. During operation, cutters should not be brought to wear levels exceeding the established optimal values accepted as the criterion for dullness.
Therefore, it is necessary to monitor the condition cutting edges and carry out timely sharpening of cutters, avoiding excessive a lot of wear or broken teeth.
Sharpening of cutters is carried out on universal sharpening machines, for example, model ZA64, or on special sharpening machines.
To ensure correct sharpening of cutters, compliance with established standards of permissible runout, ensuring the established quality of surfaces and cutting edges, it is necessary that sharpening machines and devices met the following requirements:
- Spindles of machines and devices must have sufficient vibration resistance, be well lubricated and rotate easily, axial and radial runout should not exceed 0.01 mm.
- Feed mechanisms must operate without jamming in all directions, have minimal clearances and ensure easy and smooth movement of the attached cutter.
- Replacement spindles and washers for attaching grinding wheels must ensure an accurate fit grinding wheel or a finishing disk on the machine spindle, without causing vibrations during sharpening and uneven wear of the wheel or disk.
- The total runout of the machine spindle, fixture and mandrel must be less than the permissible runout of the cutter being sharpened.
The right choice grinding wheel and sharpening modes makes it possible to obtain the specified geometric parameters of the cutting part and the required quality of the sharpened surface, which is associated with an increase in the cutting properties of the cutter.
Sharpening cutters made of high-speed steels, increased productivity - cobalt and vanadium - differs significantly from sharpening cutters made of high speed steel P18. These steels are characterized by poor grindability and increased susceptibility to burns.
Sharpening cylindrical point cutters
Sharpening of tools with a screw tooth, including cylindrical cutters, is carried out on universal sharpening machines. Cylindrical cutters with pointed teeth are sharpened along the back surface with cup and disk wheels (Fig. 206). When sharpening, the cutter is placed on a mandrel. The axis of the cup wheel is set relative to the cutter so that the circle touches the cutter being sharpened on only one side. For this purpose, the end plane of the cup circle is tilted at an angle of 1-2° to the axis of the cutter (Fig. 206, a). To form the clearance angle, the axis of the cup circle is positioned below the axis of the cutter being sharpened by the amount H (Fig. 206, b), which is determined depending on the diameter of the cutter and the clearance angle.
Rice. 206. Scheme for sharpening a cylindrical cutter with pointed teeth
If the axes of the cup wheel and the cutter being sharpened are located in the same horizontal plane, then the clearance angle a after sharpening will be equal to zero (Fig. 206, c). The position of the cutter tooth during sharpening is fixed by a stop, which is installed very close to the cutting edge.
Sometimes a special device is used to set the height stop.
When sharpening cylindrical cutters with disc wheels, the rear surface of the tooth acquires a slightly concave shape with an increased clearance angle. However, when making the right choice diameter of the grinding wheel, this concavity does not have any harmful effect.
Sharpening end mills
Face mills made of high-speed steel, as well as a number of cutters equipped with carbide plates, are sharpened in assembled form.
Sharpening of the main rear surface of end mills is carried out using the end plane of a cup grinding wheel (Fig. 207, a). When sharpening the auxiliary rear surface (Fig. 207, b), the cutter is first installed so that its auxiliary cutting edge occupies a horizontal position. Then the cutter axis is rotated in the horizontal plane by the amount of the auxiliary angle in the plan φ 1 and at the same time tilted in vertical plane to the front clearance angle α 1.
Rice. 207. Sharpening an end mill
The front surface of the cutter tooth is sharpened both by the end of the disc grinding wheel and by the periphery of the disk wheel. When sharpening, it is necessary to form the angle values φ, γ and λ specified in the drawing.
Sharpening end mills
Sharpening of end mills with a helical tooth is also carried out manually on universal sharpening machines.
Sharpening end mills along the main back surface is done in the same way as cylindrical cutters with the end surface of a cup wheel, when installing the end mill in the centers. Sharpening along the auxiliary back surface is carried out similarly to an end cup wheel. Currently, a semi-automatic model B3125 is produced for sharpening end mills with a diameter of 14-50 mm on the front and rear surfaces.
Sharpening disc cutters
Sharpening disc cutters along the main flank surface is similar to sharpening cylindrical and end mills with a cup wheel. Sharpening along the auxiliary rear surface of the end teeth is carried out in the same way as for end mills.
When sharpening end teeth along the front surface, the sharpened teeth are directed upward, and the cutters take a vertical position when the cutter has simple teeth and inclined when sharpening cutters with multidirectional teeth. In this case, the angle of inclination of the cutter axis in the vertical plane is equal to the angle of inclination of the main cutting edge.
Sharpening cutters with backed teeth
Shaped cutters with backed teeth are sharpened only along the front surface. In this case, the value of the rake angle a after sharpening should deviate from the specified value by no more than ± 1 °, since a change in the rake angle causes distortion of the shaped profile.
Cutters with straight grooves are sharpened with the flat side of the cup wheel (Fig. 208, a), and cutters with helical grooves are sharpened with its conical side (Fig. 208, b).
Rice. 208. Sharpening the front surface of shaped cutters
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. 209). Wear of backed cutters on the back surface is allowed no more than 0.5-0.75 mm. If wear is greater, the cutter should be sharpened along the entire profile, which significantly increases the cost of sharpening.
Rice. 209. Sharpening the front surface of cutters with backed teeth using a copier
Sharpening of prefabricated cutters (milling heads)
Individual sharpening of the insert cutters of prefabricated cutters can only be done on a sharpener with a tool rest or on a universal sharpening machine with the cutter secured in a three-rotary vice. When securing the cutters in a vice, in order to avoid the formation of cracks in the plates, it is recommended to place a porous rubber gasket between the movable jaw of the vice and the false tooth. Each end mill insert is finally sharpened in one setting. With this sharpening method, wear of the grinding wheel does not affect the sharpening accuracy. The rotation of the wheel when sharpening a carbide plate should be directed from the base to the cutter blade to avoid micro-chipping during the sharpening process.
In industry, end mills are used, the knives of which are sharpened as an assembly. Composite end mills are sharpened with diamond wheels ASO 8-10 B1 100% on equipment used for sharpening carbide milling cutters.
Finishing of cutters
The finishing of the working edges of the cutter is carried out primarily in order to meet the specified requirements for surface roughness. In addition, finishing allows, in some cases, to eliminate thin surface layers with burns and cracks that occurred during sharpening, and other defects of the finished surface.
Diamond and abrasive finishing are the most widely used. The finishing of carbide tools is carried out with diamond wheels on a bakelite bond, abrasive finishing is carried out with fine-grained wheels made of green silicon carbide.
Lapping is carried out mainly on tools equipped with hard alloy plates and mineral ceramics on special finishing machines. For example, diamond finishing on a strip of multi-faceted non-sharpening plates is carried out on a special finishing machine model ZV-20 in special cassettes; It is advisable to refine the supporting plane on a surface grinding machine in special cassettes with disc diamond wheels.
Finishing of carbide tools with diamond wheels provides a surface quality of a higher roughness class compared to sharpening with green silicon carbide wheels and finishing with boron carbide. When milling plastic materials with low strength and a strong abrasive effect, diamond finishing can increase the durability by two to five times compared to sharpening only with green silicon carbide wheels. This difference increases with increasing cutting speed. When milling high-strength, hard steels and titanium alloys, especially at low cutting speeds and when using brittle hard alloys, finishing with diamond wheels is either ineffective or leads to a decrease in tool life due to chipping of the cutting edges of the cutters.
Application diamond wheels type APV, APVD, AChK, AT, A1T, etc. when sharpening and finishing carbide tools with abrasive wheels, it allows you to increase processing productivity by 1.5-2 times and obtain a high quality of the machined surface (roughness R a = 0.32-0, 1 µm).
The use of composite (CBN) wheels when sharpening cutting tools made of high-speed steels also has a number of advantages compared to conventional abrasive wheels.
Checking cutters after sharpening
When inspecting cutters after sharpening, the geometric parameters of the cutting part of the cutter, the runout of the cutter, and the roughness class of the sharpened or finished surfaces are checked. A number of devices are used to control the geometric parameters of cutters.
The main requirement for these devices is ease of operation and the ability to use them directly at the workplace. In Fig. 210 shows diagrams for measuring the front and back angles of a cutter using a protractor.
Rice. 210. Schemes for measuring the geometric parameters of cutters
The goniometer consists of an arc 1 with a scale divided into marks corresponding to the number of teeth of the cutter being measured. Sector 2 moves along arc 1 and is fixed in the required position with screw 3. The sector is equipped with degree scales on which angle values are counted: front - on the v scale and rear - on the a scale. A reference ruler 4 is attached to sector 2. The rake angle, as mentioned above, is measured in a plane perpendicular to the main cutting edge of the cutter. Therefore, when measuring, the reference ruler 4 of the protractor is placed in this plane (the main secant plane). In the process of measuring the front angle (Fig. 210, a), the protractor is placed on two adjacent cutter teeth, and the protractor is supported on one and i teeth by the support ruler 4 along the cutting edge of the cutter tooth, and on the other tooth - along the front surface of the tooth by its measuring ruler 1 Ruler 1 in the groove is set in height in accordance with the size of the straight section on the front surface of the tooth. Sector 2 of the goniometer is rotated until the vertical edge of the measuring ruler 1 (knife side) aligns with the front edge and is secured in this position with screw 3.
The correct installation of measuring ruler 1 relative to the front surface is determined by light. At correct installation there should be no gap between them. The countdown is made according to right side sectors with the inscription “rake angle” against the stroke with a mark corresponding to the number of teeth of a given cutter (for example, 6, 8, 10, etc.). In Fig. 210, but it can be seen that if, for example, z = 8, then v = 10°, etc. The clearance angle of the cutter is measured in a plane perpendicular to the axis of the cutter. In this regard, the supporting surface of the ruler 4 of the protractor should also be located in this plane. With the support ruler 4, the goniometer rests on the cutting edge of the cutter tooth, and on the other tooth - along the back surface of the horizontal edge of the measuring ruler 1. Sector 2 of the goniometer is rotated until the back surface is “gap-free” aligned with the measuring edge of the ruler, which is also determined by clearance. In this case, the counting is made along the left side of the sector with the inscription “rear corner”, also against the stroke with a mark corresponding to the number of cutter teeth. In the case shown in Fig. 210, b, at z = 8, a = 27°. The accuracy of the protractor is approximately 1° 30".
Tooth runout control The cutting of cutters is carried out using an indicator in those devices where they are sharpened in center heads or in special devices.
Mills that have seat is a hole; when inspecting, it is installed on a horizontal or vertical mandrel. During inspection, cutters with a cylindrical or conical shank are installed either in a guide prism or in a device for monitoring the runout of the working part of the end tools. The runout is checked by cylindrical surface teeth, along the end teeth, along the corner edges and along the supporting end. The cutter runout is checked after installing it on the mandrel or spindle of the milling machine.
The quality of sharpening or finishing is checked by external inspection using a magnifying glass. The cutting edges of the cutters must be sharp, without nicks or gouges. The presence of cracks on hard alloy plates is determined using a magnifying glass, wetting the plates with kerosene or blowing sand on them. In this case, if there are cracks, kerosene comes out.
Security questions
- What is a growth?
- What is chip shrinkage?
- What is called the thickness and width of the cut during turning, cylindrical milling, and face milling?
- What does area depend on? cross section when milling?
- How to determine the volume of the cut layer when milling?
- What components can the resultant force during milling be decomposed into?
- What tool materials are used to make cutting tools? Area of their application?
- What is the durability of a cutting tool called and what does it depend on?
- What is the procedure for selecting milling modes?
- What is the advantage of face mills in general and with multi-faceted non-sharpening inserts in particular?
- When are diamond sharpening and finishing of cutters used?
- What methods of checking cutters after sharpening do you know?
2016-11-04
Sharpening cutters is a difficult job, requiring special training and equipment. The geometry of the cutting edges has a curved structure - this is what main feature process. The grinding wheel must follow exactly the contour of the sharp teeth of the cutter to maintain its shaped profile.
- The backed teeth are sharpened along the front surface.
- Sharply protruding cloves are processed along the back wall.
- Slotting and parting cutters are sharpened on the front and back sides.
How to sharpen cutters?
Can be sharpened manually or using grinding machine for cutters
Rice. 1.
The machine ensures synchronization different types movement and fixation of the cutter. For example, to sharpen end mill, it is necessary to combine translational and rotational movements, while maintaining a uniform pressing force of the tool against the grinding wheel. Great value has a rotation speed, abrasive grain size, and its material.
- Abrasive wheels made of electrocorundum are suitable for sharpening cutters for metal and wood (manufactured material is high-speed or tool steel of the “Standard” class).
- High-performance high-speed steel cutters are sharpened with CBN wheels.
- Diamond (PCD) and silicon carbide wheels are used to sharpen the teeth of carbide cutters.
It is important to consider that strong heating reduces the hardness of abrasives and leads to a partial loss of cutting properties. Below is a table of the thermal stability of the main materials used for the production of abrasive wheels.
Rice. 2.
To cool the sharpening tool during operation, water alone will not be enough - the machine will rust. Experts advise adding soap and soda ash, nitrite, sodium silicate, etc. to the water. — electrolytes create a protective film on the surface of the grinding wheel.
There are more than 20 sharpening wheel configurations for sharpening milling tool. The back planes of the incisors are ground with disc-shaped or cup-shaped wheels, the front ones - flat or disc-shaped.
Rice. 2.1
Automated sharpening modes
You cannot sharpen carbide tools in “hard” operating modes of the machine - the edges of the teeth may become chipped.
The average peripheral speed of a grinding wheel for processing hard alloys should not exceed 10 - 18 m/sec. This means that for a circle d 125 mm 2700 rpm is the maximum engine rotation rate. For more soft materials It is enough not to cross the threshold of 1500 rpm.
Technology for sharpening cutters on a machine
The cutter is fixed in its original position, then the machine is turned on and the tool is slowly brought to the grinding wheel (until it sparks). The moment comes to set the thickness of the metal layer to be removed, usually no higher than 50 microns and no less than 25 microns.
Sharpening is done on each tooth separately. The machine needle must constantly be in contact with the surface of the cutter; sharpening begins by placing the needle in the tail groove of the tooth. The machine is turned on and, gradually retracting the spindle with the cutter, the procedure is performed.
The skill of a professional is to maintain a uniform sharpening stroke on all cutting edges. The same movements will need to be repeated several times for each tooth.
Different types of cutters require different movements
How to sharpen a cutter by hand?
A shaped end mill for tough materials (wood) can be sharpened by hand without resorting to expensive equipment. You will need:
- desktop and bar made of steel or hardwood;
- diamond block;
- abrasive wheel;
- solvent;
- water with soap or lye;
- sandpaper.
Rice. 3.
The diamond bar is fixed on the edge of the table and moistened with soapy water. The cutter must be freed from the bearing (if there is one) and cleaned of any remaining wood resin. The size of the rake sharpening angle varies in the range:
- 10 - 20 ⁰ for wood cutters;
- - 5 - 0⁰ for tools for metals (mainly for steels).
The range of the sharpening angle of the back surface is wide and is not limited by the indicators.
Sharpening is done with smooth movements along the diamond stone.
You need to try to make the same number of movements of the cutter on the block with the same pressure force. As the cutting edges become sharper, the abrasive grain size decreases, final stage processing can be done with sandpaper.
The sharpening result is assessed visually using a magnifying glass or kerosene. The teeth should not contain even small nicks or cracks. To detect microcracks, the surface of the cutting edge is moistened with kerosene - in the area of the crack, the kerosene will appear more strongly. Notches and microchips are determined by eye or through a magnifying glass.
If you manage to obtain the proper quality and know how to use the tool carefully, then the need for sharpening comes much later than in cases with low-quality products. Large selection high-quality cutters (about 20 types) are always available in the Rincom store. It is convenient to select and order tools of the widest profile on the Internet; today it is not dangerous and modern.
An operation such as sharpening a wood cutter is not so simple. This process requires certain knowledge and skills.
Buying wood cutters in Kyiv and other cities is now not a big problem. But sooner or later the highest quality of them will become dull, and then it will have to be sharpened. How to do this correctly?
Wood cutter: basic rules for sharpening
The teeth of the product can be completely different. The inclination of these elements can be different and is characterized by the main part of the edge. The parameters for determining the appropriate teeth depend on the tool, as well as the features of the product you choose.
The process of sharpening a cutter can be done without special expensive equipment, since you can use diamond stones small thickness. In this case, you need to use plain water or a liquid with a soap solution. When the sharpening process comes to an end, you should wash and dry the tool.
First, the cutter must be dismantled. The main thing is that you do not forget to clean it of resins and wood. An ordinary solvent can cope with these tasks.
To effectively solve these problems, you must choose quality materials. If you do not do this, then the work will not bring the desired result.
- you need to use bars with different levels graininess. This setting depends on the material you are going to remove;
- The purity of the base, which you initially determined, plays an important role. Before you carry out the sharpening process, you should make sure that the beam will be of the shape you need;
- symmetry is preserved only if you try to create a configuration similar to the movement of the cutters during the process of sharpening the product;
- if the material of the teeth is quite soft, then replace the beam with abrasive paper, which will provide a perfectly even base;
- the end products are sharpened on the device that is intended for this purpose. The wheel does not spin very quickly, so you will have to buy an abrasive product.
Of course, the process of sharpening a cutter takes a lot of time. However this resource will pay off over time, because you will do your job with maximum effect.
These are the main points that relate to this field of activity. You must take into account all the nuances in order to achieve maximum results, because all other rules will not provide you with the same effect.
Quick cleaning and sharpening of wood cutters. Or how to sharpen an end mill with your own hands:
Sharpening cutters is an operation to restore cutting properties that were lost as a result of tooth wear.
The modern equipment that our company uses allows us to sharpen cutting cutters with perfect accuracy:
- When sharpening cutters, like any other tool, we comply with all the necessary parameters;
- We ensure the maximum number of tool sharpenings in the future;
- We provide the best performance when processing materials, no chipping, increased service life of the cutter between sharpenings.
Well-done sharpening of a cutter increases its durability, which significantly reduces the consumption of cutting tools. If you operate the cutter sufficiently for a long time or you are just planning to use it, then remember that the amount of wear on the cutter should not exceed the established optimal values, which are accepted as the criterion for dullness. In order to preserve the cutter in its almost original form, it is necessary to monitor the condition of the cutting edges and, of course, sharpen the cutter in a timely manner, trying to prevent too much wear or breakage of the teeth.
As a rule, sharpening of a disk cutter is carried out on universal sharpening machines. In order for the sharpening process to occur correctly, it is necessary to comply with the existing and introduced certain standards of permissible runout, established quality assurance of cutting edges and surface quality.
Our company offers you the job of high quality. By contacting us, you are contacting highly qualified professionals who approach their work with full responsibility.
We will provide sharpening of cutters long life and the performance of your tool will ensure reliable operation, since a dull cutter is very dangerous! Keep this in mind when performing a specific task where you may need to this tool. And in case of problems or approaching the end of the resource cutting discs- contact our company.
Rules for accepting disc cutters for regrinding
1. To sharpen disc cutters, an “Agreement for the processing of customer-supplied raw materials” must be concluded between the customer and the contractor.
2. Milling cutters are accepted only if there is an M-15 delivery note from the Customer, in which it is necessary to indicate the contract number and the range of disk cutters.
3. When handing over cutting disc cutters for regrinding, the Customer must receive from the Contractor an “Inspection Order” signed by the Contractor, which indicates the cost and deadline for completing the work.
4. Receipt of cutters is carried out only by proxy.
A cutter is a type of round rotating cutter. Its cross section always contains a circle, and the shape itself can be any, including very complex ones. There are grooves (of varying depths) or denticles along the circumference. They process the material during the rotation of the cutter. – the process is complex and painstaking. It is important that not only the specialist has a certain level of skill, but also that 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 performance of milling work.
Varieties
Cutters come in a variety of types - end, end, disk, slotted, cylindrical, groove. And these are not all varieties. They are also divided according to purpose and are angular, shaped, keyed, for T-slots. Another division is based on the type of surface being processed:
- for metal;
- on wood;
- on plastic;
- on glass;
- and others.
Sharpening cutters for metal complex due to the large length of the cutting surface. This work is only possible when using special tools. IN in some cases you have to grind it by hand, but for this you need to have a lot of experience. Otherwise, all previous work will go down the drain. The grooves (teeth) will show nicks, gouges, chips and cracks. The part will have to be ground again, which invariably reduces its size.
