Device for sharpening circular saw blades with your own hands
Device for sharpening circular saws with their own hands
Most cutting tools get dull during use. This also applies, to a large extent, to circular saw blades that need to be sharpened on a regular basis. This is what guarantees a really high-quality sawing of wooden products. The easiest way to sharpen dulled teeth is to use a standard file.
But in order for the work with your own hands to be fully fruitful, you need to seek help from a true professional. Only he is able to sharpen cutting tools so that they can be expertly used.
Much easier and more effective in such a situation to use a machine, made by your own hands, for high-quality sharpening of sharp surfaces of saws, as well as the unit for processing circular knives.
- Making a saw sharpening machine yourself
- JMY8-70 machine. benefits and features
- The process of sharpening circular saws with your own hands
Circular saws. what they are
Circular saw blade, if properly sharpened and set teeth, is able to qualitatively and accurately cut the workpiece in any direction of the cut relative to the fibers.
There are several types of circular saw blades:
Circular carbide circular saw. Characteristics
- Circular saw blades with a base and a cutting area of solid metal;
- Blades with a base of solid metal and sprayed materials of hard structure on the teeth;
- Metal blades with tungsten carbide tips.
Cutting quality workpieces is not possible if the teeth are worn out or blunt. A side effect of blunt tools is excessive strain on motor, risk of jamming and cutting operations that are not safe. Circular saws need to be sharpened.
Only saw blades with special grooves may be used for cutting hardwood. Technological breaks on the blade prevent general deformation of the tool in case of possible heating during work. That eliminates vibration background and cutting line deterioration.
Several kinds of circular saws are used for circular sawing. Hand-held models use circular saws made in industry, home-made components are very rare. But for stationary circular saws are used both factory and homemade.
If you take a professional tool, then for it are used:
- Saws with tungsten carbide tips. For this purpose, bobedite, a special refractory steel for cutting tools, is most often used.
- Circular saws with hardened teeth.
- Saws in tool steel for all applications.
- Tools for working with special materials. plywood, plastic, asbestos cement boards and even stone.
Important! Grinding circular saws of each kind has its own peculiarities that not only need to be known but also the technology and work sequence should be strictly followed.
The need for sharpening
Sharpening circular saw blades when cutting is no longer possible. This can be understood from the three signals:
- The guard is heating up. Smoke appears from underneath, exits the cutting zone.
- The need for additional forces at the feed of the workpiece during cutting.
- Wood comes into contact with the cutting metal and causes burning and smells.
The geometry of the carbide teeth
A carbide tooth has four working surfaces. one at the front (A), one at the back (B), and two auxiliary side surfaces (C). These planes intersect to form the main (1) and two auxiliary (2 and 3) cutting edges. Given definition of tooth edges and edges is given according to GOST 9769-79.
Straight tooth. Typically used in saws for longitudinal quick sawing, where quality is of little importance.
Oblique (beveled) tooth with left and right angles of the back plane. Teeth with different bevel angles alternate with each other, so they are called alternate bevels. This is the most common tooth design. Depending on the size of the resharpening angles, saws with an alternate bevel tooth are used for cutting all kinds of materials (wood, chipboard, plastics). both in the longitudinal and transverse directions. Saws with a steep back angle are used as scoring machines to cut double sided laminated boards. This prevents chipping of the coating on the edges of the kerf. Increasing the bevel angle lowers the cutting force and reduces the risk of chipping, but also reduces tooth strength and durability.
Oblique teeth with beveled back plane
Teeth can be beveled not only on the back plane but also on the front plane.
Oblique tooth with beveled front plane
Trapezoid tooth. These teeth have relatively slow blunting rate of cutting edges in comparison with alternate teeth. They are usually used in combination with a straight tooth.
Alternating with and slightly above the last tooth, the trapezoidal tooth performs roughing while the straight tooth following it performs finishing cuts. Saws with alternating straight and trapezoidal teeth are used for cutting double-sided laminated panels (chipboard, hardboard, wood-fibre board etc.), for example in the wood industry.) as well as for sawing plastics.
Conical tooth. Saws with conical teeth are auxiliary and are used to cut the lower layer of the laminate and prevent it from chipping when the main saw penetrates it.
The vast majority of teeth have a flat leading edge but there are also saws with a concave leading edge. They are used for finish crosscut sawing.
Tooth sharpening angles
There are four basic angles of sharpening of the circular saw which, along with the shape of the tooth, determine its characteristics. These are the rake angle (γ), the back angle (α) and the bevel angles of the front and back planes (ε1 and ε2). The sharpening angle (β) has an auxiliary value as it is given by the front and rear angles (β=90°-γ-α).
The values of the sharpening angles are determined by the purpose of the saw. t.е. what material it is designed to cut and in what direction. Saws for longitudinal sawing have a relatively large rake angle (15°-25°). For crosscut saws, the angle γ usually varies between 5° and 10°. Universal saws intended for cross and longitudinal sawing have an average value of the front angle. usually 15°.
Angle values are not only determined by cutting direction, but also by the hardness of the material to be sawn. The higher the hardness, the smaller the front and back corners should be (less tooth sharpening).
The rake angle can be either positive or negative. Saws with this angle are used for cutting non-ferrous metals and plastics.
Main saw tooth wear occurs on the top edge that is directly involved in cutting. Its rounding can be 0.3 mm. The central edge changes earlier than the others.
Circular saw blade sharpening
Material and properties of carbide tines
Circular saw blades with tungsten carbide teeth consist of blade (disk) made of 9XF, 65G, 50XFA and other steels., and carbide plates acting as cutters.
In domestic saws as material for cutting plates the sintered tungsten-cobalt alloys of BK marks (BK6, BK15 etc.) are used. The number indicates the percentage of cobalt). Hardness of BK6 is 88,5 HRA, BK15 has 86 HRA. Foreign manufacturers use their alloys. BK hard alloys consist mainly of cobalt-cemented tungsten carbide. The characteristics of the alloy depend not only on its chemical composition, but also on the grain size of the carbide phase. The smaller the grit, the higher the hardness and strength of the alloy.
Carbide inserts are attached to the disk by high temperature brazing. As the soldering material, in the best case, silver solder (PSr-40, PSr-45) is used, in the worst case. copper-zinc solder (L-63, MNMC-68-4-2).
Geometry of carbide teeth
The carbide tooth has four working planes. the front (A), the back (B), and two auxiliary side planes (C). These planes intersect each other to form the main (1) and two auxiliary (2 and 3) cutting edges. The given definition of tooth edges and facets is given according to GOST 9769-79. Carbide tooth of the saw blade
Tooth shape is used to distinguish between the following types of teeth.
Typically used in saws for longitudinal quick cuts where quality is of little importance.
With left and right angled backplane. Teeth with different angles of inclination alternate with each other and are thus called alternately angled. This is the most common tooth shape. Depending on the size of the resharpening angles, saws with an alternate toothed plane are used for cutting in both longitudinal and cross direction in many different materials (wood, chipboard, plastics). Saws with a steep back angle are used as a scoring tool when cutting double sided laminated boards. Their use avoids chipping of the coating on the edges of the kerf. Increasing the bevel angle reduces the cutting force and reduces the danger of chipping, but also reduces the durability and strength of the tooth.
Beveled Back-Plane Tooth
Teeth can be offset not only on the back plane but also on the front plane.
Bevel tooth with beveled front surface
The feature of these teeth is a relatively slow blunting rate of cutting edges in comparison to alternate-slotted teeth. They are usually used in conjunction with a straight tooth.
Alternating teeth of different shapes
Alternating with the last tooth and rising slightly above it, the trapezoidal tooth performs roughing sawing, and the straight tooth following it performs finishing sawing. Saws with alternating straight and trapezoidal teeth are used for cutting double-sided laminated panels (chipboard, hardboard, hardboard and so on) as well as for cutting plastic, wood, woodchipboard and so on.) and for cutting plastic materials.
Saws with a tapered tooth are auxiliary and are used to notch the bottom layer of the laminate, protecting it from chips when the main saw passes through.
The vast majority of teeth have a flat leading edge, but there are also saws with a concave leading edge. They are used for finishing crosscut sawing.
Tooth with concave front surface
Tooth rake angles
There are four basic angles of sharpening of the circular saw, which, along with the shape of the tooth, determine its characteristics. These are the anterior angle (γ), the posterior angle (α) and the anterior and posterior bevel angles (ε1 and ε2). The angle of sharpening (β) is of auxiliary importance as it is given by the anterior and posterior angles (β=90°-γ-α).
Circular saw tooth angles
The values of the cutting angles are determined by the intended use of the saw. t.е. Angles of resharpening are based on the material to be cut and the direction in which the circular saw blade is to be used. Saws for longitudinal sawing have a relatively large rake angle (15°-25°). Crosscut saws generally have an angle γ between 5 and 10°. Circular saws designed for cross and rip sawing have a median rake angle of typically 15°.
Sharpening angles are not only determined by cutting direction, but also by the hardness of the material being sawed. The higher the hardness, the smaller the front and back corners should be (less tooth sharpening).
The rake angle can be not only positive, but also negative. Saws with this angle are used for cutting non-ferrous metals and plastics.
Basic sharpening principles
Main wear of carbide tooth occurs along its main (top) cutting edge. In the process, the latter is rounded to 0.1-0.3 mm. The leading edge wears the most rapidly of all facets. When cutting massive workpieces, the side edges are also subject to quick wear.
Avoid excessive dulling of the saw blade. Radius of cutting edge rounding must not exceed 0,1-0,2 mm. In addition to the fact that a severely blunted saw has a dramatic drop in productivity, it takes several times longer to sharpen it than a normally blunted saw. The degree of blunting can be determined both by the teeth themselves, and by the type of kerf they leave.
Sharpening by yourself is not difficult. Especially if you have the necessary equipment. And if not, you can make it with your own hands. To make a machine for sharpening circular saws, whose price will only please you, you can use simple parts. To do this you will need the following basic elements:
The wheel is fixed on the motor, disk blade. on the slide, screws will ensure movement of the workpiece along the axis of the wheel, which will provide the desired angle.
The main task for such an element, as a machine for sharpening circular saws, is their fixation in the required position relative to the wheel. It is necessary for the exact observance of angles, it can provide a stand, mounted on the frame of the machine in the same plane as the wheel.
When positioning the blade on the stand, the teeth must be perpendicular to the plane of the saw blade.
Grinding by hand
If you don’t have a machine, you can sharpen it with a file. For this it is important to clearly fix the disk. This is done by means of a vice. If the blade is not removed from the circular saw, you can do without them. Bars are inserted between the teeth, and the tool is set against a vertical plane.
At any point on the circle a marker is made. This way it will be clear when the work is finished. Work is done with a flat file that fits well between the teeth. The most subject to wear is the top edge of the tooth and its leading edge.
First the back surfaces of the teeth are sharpened all around the circle. In the second stage the front faces are sharpened. It is important to remember that the applied force must be equal, then all the teeth will be evenly sharpened.
Sharpening of the circular saw blade is realistic at home. For this purpose it is better to buy a simple machine. In his absence, you can use a vice or homemade stops. Checks tool on completion of work. The sawing process should be smooth and quiet.