At present, a sufficiently large number of cutters of various sizes are produced. They can be classified by functional and constructive qualities.
Machine for sharpening end mills.
Sharpening end mills is performed using special devices for similar tools. In some cases, sharpening can be done manually.
The cutters have a relatively large length and roughness of the 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 milling cutters that have a cornered angle. You should know that sharpening is quite difficult. In order to preserve the profile of the structure and facilitate the process of sharpening, the ground teeth should be sharpened solely on the front base. Sharp teeth, which have a smooth or curved shape, should be sharpened solely on the back of the base. Slitting and cutting mills can be sharpened on the front and rear bases of the teeth.
Geometry teeth milling cutters
The geometry of the teeth of the cutter: a - sharpened tooth, b - ground tooth.
To make sharpening correctly, you need to know the geometry of the teeth of the cutter. According to the design of the teeth, the milling cutters are distinguished with ground and sharp teeth. The latter part of the rear base, which is adjacent to the edge for cutting, is a plane. Sharp-edged teeth, in most cases, are sharpened on the back base, but they can be sharpened on the front base of the tooth.
In the ground teeth, which come complete with end mills, the rear base is made in a spiral of Archimedes. Technologically it is difficult to process the shaped base, therefore it is possible to sharpen mills with ground teeth only on 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 front and rear corners, the size of the grinding area, and the angle of inclination of the teeth.
The ground for sharpening is an element of the rear base of the clove, which is polished during the grinding process on the rear base. On this basis, maximum wear of the teeth will occur. Its size affects the magnitude of the friction force between the tool and the workpiece, because the base must be maintained in a specific range.
The scheme of sharpening precast cutters on a universal sharpening machine.
The main 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 edge for cutting.
Main rear angle - the angle between the tangent to the rear base at a given point of the main edge for cutting and tangent to the plane of rotation of this point. This angle helps reduce friction between the tool and the workpiece.
With the help of an auxiliary rear corner, a large clearance between the milled base and the body of the clove can be characterized. You need to sharpen the tool at an additional angle for a specific amount of damage to the tool and increase the area for sharpening. The purpose of this action is to reduce the friction between the clove and the milled workpiece. Please be aware that not all tools of this type have this angle.Back to table of contents
How to sharpen end mills for processing wood?
Sharpening end mills on wood.
The shape of the teeth can be straight or screw. The inclination of the teeth of the tool can be described as the angle between the screw-type reversed edge and the axial part of the tool.
The angles of the teeth will depend on the type of tool, alloy and steel grade 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 chosen in the range of 15-20 ° or more. For hard metal tools for steel milling, the angle will be 0 ° or -5 °. Rear angle varies over a wide range.
Items that will be needed:
- Diamond beam.
- Water or solution with soap.
- Abrasive paper.
- Hardwood plank or steel strip.
- Abrasive wheel.
It is possible to sharpen shaped end mills without special devices for sharpening, on the front base with a diamond bar of small thickness. The bar must be installed on the extreme part of the table. If the tool has a large notch, then the tool needs to be fixed along the table.
Table of heat resistance of various materials, ° C.
When sharpening the timber will need to be moistened with clean water or a solution with soap and water. 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 it must first be dismantled, and then sharpened. An attempt 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 the trees. For this it is best to use a solvent.Back to table of contents
Tips to Know
In the process of sharpening tools will need to use bars of different grain sizes. The grain size will depend on the thickness of the material layer to be removed and the desired purity of the base. Before sharpening it will be necessary to make sure that the bar has a suitable shape.
In order to maintain symmetry, in the process of sharpening each cutter, it will be necessary to try to make an identical number of movements, while the pressure must also be the same.
Figure 1. Shapes of circles for grinding.
If the teeth of the cutter are made of relatively soft material, instead of a bar, you can use abrasive paper, which is glued on a flat base. As a base, you can use a hardwood bar or a steel strip.
End mills for milling wood sharpened on a special device with a low speed of rotation of the circle. In this case, you will need to use a suitable abrasive wheel.Back to table of contents
Sharpening modular cutters can be made circles of white or ordinary electrocorundum, diamond and others. For example, using electrocorundum wheels, it is possible to qualitatively grind cutters for working with metal and wood, which are made of tool or other steel of standard productivity. Elborovye circles have the ability to sharpen the design of high performance steel. Silicon carbide and diamond wheels are used to grind hard metal cutters.
Before using abrasive wheels it is recommended to cool them. One of the major flaws in the diamond wheel is the relatively low resistance to high temperatures. At a temperature of about 900 ° C, the diamond will burn.
By increasing the temperature, the hardness of such a device is reduced. A temperature of 1000 ° C can reduce the hardness by almost 2 times. At a temperature of 1300 ° C, this figure will drop about 6 times.
Figure 2. Sharpening end mills: a - the main cutting edge, b - an auxiliary cutting edge, c - installation scheme 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, you need to add soap and some electrolytes to the water, which can form films for protection. When grinding almost always use a solution with soap or soda. If you are finishing grinding, you should use a low-concentrated emulsion.
To increase the quality of grinding with an abrasive wheel and reduce significant damage, it is recommended to choose the maximum grit that is able to provide the necessary cleanliness class for the base of the cutter used.
The circumferential speed of the circle during grinding of hard metal teeth should be approximately 15-18 m / s. For example, in the process of applying a circle with a diameter of 12.5 cm, the rotation speed of the engine should be approximately 1600-2700 rpm. If you need to sharpen more brittle materials, you need to perform actions at a lower speed. In the process of using tools from solid metals, the application of a hard regime leads to the appearance of high stresses and cracks, and in some cases, damage to the edges for cutting. The wear of the circle in this case will increase.
The shape of the circle for sharpening the posterior angle of the teeth on the basis of the cylindrical shape should be a cup or a plate. For sharpening the front corner you need to use a disc or flat circle.
Existing grinding wheel shapes can be seen in (Fig. 1).Back to table of contents
Sharpening side and end teeth
Such a device should provide all the necessary movements of the cutter, which is sharpened.
The side teeth are sharpened as follows:
Sharpening the end mill: a - the main cutting edge, b - the auxiliary cutting edge.
- Cutter will need to install in the collet.
- The needle must be installed in such a way that it is located in the highest position. Its end must be in contact with the outer edge of the groove of the end mill.
- The tool must be installed in such a way that the needle is near the tail, resting on the groove of the tooth.
- Using the side shift lever, the grinding wheel must be moved to the position in which its outer edge coincides with the needle.
- Next you need to turn on the engine.
- Using the lever for feeding, you need to bring the circle to the cutter at low speed until sparks begin to appear.
- Using the scale you need to determine the thickness of the metal to be removed.
- The sharpening of the tooth over its entire length is performed by retracting the spindle with the tool until the tool comes off the needle. In this case, it will be necessary to ensure that the tool is in continuous contact with the needle. In this way, it is possible to ensure that the cutter scrolls, used so that the installed part contacts the wheel in the same position.
- To ensure the purity of the milling cutter pass must be repeated one more time.
- Similar actions need to be repeated for all sharpened cloves.
To sharpen the teeth was uniform, it is not necessary to change the thickness of the metal to be removed, determined with the help of the direct feed lever at the very beginning of the work.
End teeth can be sharpened as follows (Fig. 2):
- The end mill should be installed so that the tooth is placed exactly horizontally. Horizontality can be achieved by using a square.
- Sharpening teeth is performed by moving the edge of the circle along the edge of the teeth. The sharpening angle can be adjusted by shifting the circle vertically or by tilting the spindle with the tool.
At the end of the cutter must be checked for the presence of chips, cracks and other defects. Also need to check the roughness of the base.
Sharpening end mills is an easy process, it is only important to know all the nuances and have the necessary tools to work.