How to sharpen a carbide-tipped saw blade?
Checking your circular saw for wear is an important consideration. Deep damage makes it impossible to sharpen the circular saw blade. There are three basic signs that tell you when a saw needs sharpening or replacement:
- Severe heating of the protective cover and smoke formation. A circular saw has a special guard that signals that the saw has blunted through heat. In severe cases smoke may be produced.
- Sometimes the saw is designed with a mechanical feed (if it is necessary to adjust the pressure manually). In this situation wear can be noticed if the pressure has to be increased.
- If the sawing of wood produces soot and a strong, unpleasant odor on the workpiece.
All of the situations described above tell the user that it is time to sharpen the device.
Important features
In order not to let the readers get lost in the maze of modern circular saws market we have prepared 5 main criteria that will help to decide the right choice. Let’s consider them in order of importance.
Read also: Why do you need a choke in a power supply?
Outer diameter
Outer, or outer diameter of blade must not exceed the circular saw blade guard dimensions, otherwise it can not be fitted in the arbor. A larger setting results in a greater cutting depth. Characteristic ranges from 65 mm to 500 mm.
Fitting diameter
Seating, or inside diameter. the size of the hole in the center of the tool. Determines whether a saw blade is suitable for mounting on the spindle. Most popular sizes: 16, 20, 22, 30 and 32 mm. But the full range is much wider. from 11 to 50 mm.
The manufacturers can install pins on the saw’s seat for additional fixation. In this case, choose a disc with the appropriate holes.
Number of teeth
The higher the number of teeth the faster the cutting speed but the cleaner the cut. And vice versa: the fewer cutters, the faster the work, but the more imprecise the cut. The characteristic has its own classification, presented in the table:
| № | Name | Number of teeth, pcs |
| 1 | Large | 80-90 |
| 2 | Medium | 40-80 |
| 3 | Small | 10-40 |
Tooth rake angle
Grinding inclination. deflection angle of the cutting edge of the tooth from the radius of the circular saw blade. The picture clearly shows how this characteristic influences the process. The angles are as follows:
Standard: 5 to 15°. Universal sharpening. Suitable for all types of sawing.
Positive: 15-20°. Ideal for longitudinal sawing due to the “grip” effect.
Negative: down to.5°. Suitable for cross-cutting, no splintering.
disc thickness
Standard parameter is 3.2 mm. The thinner the disk, the more it heats up and fails faster. Its greater thickness ensures a longer tool life, but slows down the work. In this case there is an increase in material overrun due to the wide kerf.
Sharpening with a machine
If there is an opportunity to purchase a special machine, then the process in question can be carried out with maximum efficiency. Such a device has compact dimensions, it can be used at home.
Particular attention is paid to the choice of grinding wheel. In this case, note the nuances below:
- The carbide disc is difficult to sharpen.
- When selecting, look for elbor, diamond or green silicon carbide grinding wheels.
The sharpening process is very simple when using professional equipment. Grinding wheel is fastened by means of a special locking device. It is designed with the design features of the wheel in mind. Let’s pay special attention to the fact that with the use of special machines it is very easy to sharpen circular saws with the necessary indicators. In this case the error is minimal. This is because the design has a special angle gauge. In order not to make a mistake at the time of work which teeth have already been machined, the starting point should be marked with a marker.
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Carbide-tipped circular saws can lose their initial cutting capability over time. But that does not mean that you have to buy a new cutting tool. In most cases, sharpening can be done at home, using any suitable machine.
How to determine the sharpening angle of a circular saw
Carbide tip geometry
It is best to have an initial template that can be used to modify cutting edge geometry. Often it is made of thin-walled stainless steel, less often. of thick cardboard.
Carbide inserts are made according to GOST 9769-79. But their geometry and geometrical dimensions are defined by the manufacturer according to the purpose of the saw. If you do not have a template, you must determine the necessary sharpening angles yourself. For this purpose it is recommended to use a pendulum-type angle gauge.
The technology for making a template with your own hands.
- Take a new soldered disc that is identical to the blunt disc.
- Draw an accurate outline on a hard piece of cardboard.
- Using a pendulum angle gauge, determine the initial geometry of the carbide tips.
- Record the data on a template.
Afterwards it can be used for self-sharpening on the machine or provide as a sample to companies providing similar services.
Additionally it is recommended to compare the obtained data with the reference ones. In saws for longitudinal shaping, the rake angle is usually between 15° and 25°. For transverse models, this varies from 5 ° to 10 °. On universal models, front angle of 15°.
It is important to remember that the rake angle can be negative. Similar models are used to cut plastic sheets and non-ferrous metals.
Sharpening is necessary
Sharpening circular saw blades when cutting becomes impossible. This can be understood from the three signals:
- Heating the blade guard. Smoke emerges from underneath, exits the cutting zone.
- Additional effort required to feed the workpiece at the time of cutting.
- When wood comes into contact with the cutting metal, there is a burning and smelly odor.
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Carbide tooth geometry
A carbide tooth has four working planes-the front (A), the back (B), and two auxiliary side planes (C). These planes intersect to form the main (1) and two auxiliary (2 and 3) cutting edges. The given definition of tooth edges and edges is given according to GOST 9769-79.
The following tooth types are distinguished by shape.
Straight tooth. Generally used in saws for fast, longitudinal cuts 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 “cross beveled. This is the most common tooth design. Depending on the size of the sharpening angles, saws with an alternate bevel tooth are used for cutting various materials (wood, chipboard, plastics). both longitudinally and transversely. 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 kerf edges. Increasing the bevel angle lowers the cutting force and reduces the danger of chipping, but also reduces the durability and strength of the tooth.
Oblique Tooth with Beveled Back Plane
The teeth can be inclined not only on the rear but also on the front plane.
Bevel tooth with beveled front surface
Trapezoid tooth. These teeth have relatively slow blunting rate of cutting edges in comparison with alternately beveled teeth. They are usually used in combination with a straight tooth.
Alternating with the last tooth and rising slightly above it, the trapezoid tooth performs roughing while 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, fiberboard, etc.).) as well as for sawing plastics.
Conical tooth. Bevel toothed saws are auxiliary saws and are used to notch the bottom layer of laminate, protecting it from splintering as 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 clean crosscutting.
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 front angle (γ), the rear angle (α) and the bevel angles of the front and rear planes (ε1 and ε2). The angle of sharpening (β) is of relative importance as it is defined by the rake angle (β=90°-γ-α).
Sharpening angles are determined by the purpose of the saw. i.e.е. which material it is designed to cut and in which direction it is to be cut. Saws for longitudinal sawing have a relatively large front angle (15°-25°). Cross-cutting saws usually have a cutting angle γ of between 5° and 10°. Universal saws designed for cross and rip sawing have a median rake angle of typically 15°.
Sharpening angles are determined not only by the direction of cutting, but also by the hardness of the material to be sawn. The higher the hardness, the smaller the front and back angles 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.
Tools
Doing saw sharpening with your own hands is allowed only with the use of special devices. There is a sharpening machine for this, which helps to carry out the process on an automatic rather than manual. Then the result becomes more accurate.
In addition, other handy devices are used for sharpening:
There is no substitute for the aids listed above. If at least one of them is not available, it will not be possible to sharpen the saw.
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Tools
To do the sharpening of the saw with their own hands is allowed only with the use of special devices. There is a sharpening machine for this, which helps to carry out the process automatically instead of manually. Then the result is more accurate.
In addition, other handy devices are used for sharpening:
There is no substitute for the listed fixtures. If at least one of these is not available, sharpening is not possible.
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Grinding of circular saws with Pobedite tips
Carbide-tipped circular saws have difficult sharpening angles to maintain because the tooth is tapered. This alloy is attached by soldering. Cutting geometry is complex and resharpening parameters need to be precisely calibrated.
Work is carried out by smoothing the cutting edge to a radius of 0.3 mm. Do not allow for larger values.
- Sharpening is performed on the front and the rear surface of the tooth. If the work is performed correctly, the total number of sharpenings to the complete wear of the blade will be 30 times.
- Work should begin with the front plane.
- The portion of the tooth that has a burr should fit snugly against the cutting wheel.
- Turning time of 3 to 5 seconds. No longer possible. This leads to overheating of the metal. It is overhardened and tempered with a decrease in hardness.
- Thickness of the material to be sharpened is in the region of 0.15 m.
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How to sharpen the circular saw with your own hands
To sharpen the saw at home you can absolutely independently. For this purpose, there is no need to visit a workshop to use a specialized sharpening machine or buy one. It is quite expensive and is rarely used for sharpening, unless of course you plan to use it for large production purposes.
But holding circular saw blades in your hands while you sharpen the teeth with a grinding wheel is not the best solution. Circular saw blade is not a drill, it is much more bulky. No hardness of hands and excellent eyesight will allow, to make sharpening so that cutting elements are sharp enough and suitable for effective use. To do this, you must provide the simplest fixing device.
To hold the toothed circular wheel in the desired position in relation to the plane of the sharpening tool, you can use the most ordinary flat stand.
Its surface position must correspond to the level of the axes on the rear disk. Tooth wheel is placed on the stand so that the sharpened tooth plane is perpendicular to the saw blade blades. To sharpen beveled teeth on front and back surfaces, it is necessary to provide movable joints in this fixture.
But in such cases it is quite difficult to maintain the same value of front and back angle. To avoid this problem it is necessary to fix the center of the saw rigidly to the sharpening wheel. This is done by means of slots for mandrel, which is mounted on the stand with placing of sharpening saws on it, or by means of installation on the stand of special support, which fixes the saw blade according to the required angle to the abrasive stone.
If you adhere to all the requirements for sharpening a carbide circular saw, then this tool will work as effectively as possible for a long period of time.
Methods of machining circular blades
To form the cutting edge, any sharpening machine is suitable, where the design of the equipment does not matter much. Of course, the sharpening angles of carbide-tipped circular blades are obtained more accurately on specialized equipment. However, its cost is very high, so an ordinary sharpening machine with a possibility to change the inclination of the corundum disc is used.
To sharpen a circular disk yourself, you must strictly follow a few basic conditions:
- It is usually the top edge that is deformed. Sometimes the rounding of edges is up to 0,3 mm. Therefore, sharpening begins at the top.
- Processing is carried out taking into account the front edge and its back part.
- The operation should be repeated at least 25 times. The thickness of the removed metal should not be more than 0,05-0,15 mm.
- Processing quality must be absolutely identical on the processed surface.
- After sharpening, it may be finished by hand, using fine grit emery paper.
Sharpening carbide-tipped tools
Sharpening circular saws with pobedite tips often causes problems. Processing with standard abrasives takes a very long time, and if the material is overheated, it is possible to “temper” it. Of course, machining with a diamond tool is much faster, but the cost is very high. It is much more economical to buy a whitewash blade.
Every craftsman approaches this problem strictly individually. To get the correct sharpening angles for carbide-tipped circular saws you will absolutely need a sharpening machine.
Cutting geometry
The saw blade, the tooth, has a defined geometry with more than one cutting edge. There is always one main groove and additional grooves formed by intersecting planes “A”, “B” and “C” in certain combinations. For various materials, it makes sense to choose discs with the most suitable tooth shape.
Straight tooth
The saw blade with this working area is designed for rough cuts in lumber. The cut is coarse and of poor quality, with relatively fast operations.
Tooth beveled
A cutting edge front plane with this shape produces cuts with a precise and straight line. Ideal for cutting composite materials: plywood, chipboard (single- and double-sided laminated). After cutting hardwood blanks, it is scalloped out, with almost no splintering observed.
There are discs with a beveled leading edge, there are discs with a beveled trailing edge, or a version with alternate teeth (alternately beveled blade). Cutting hardwood with a beveled back edge produces a clean cut but dulls the saw very quickly.
Trapezoidal tooth
The main advantage of this type of saw is the slow wear of the blade due to the lack of the need for frequent sharpening in a sharpening machine. Usually the entire blade trimmer blade consists of alternating cutting elements. straight and trapezoidal teeth working in tandem. The higher trapezoid tooth performs a rough cut, allowing the main straight edge to cut more easily. The tool can be used to cut plastics, hard laminates.
Tapered tooth
Auxiliary tool type designed to make cuts in laminated materials before the main cut. The operation is carried out to avoid the appearance of chips on the front part of the product. This circular saw blade cannot be used as a standalone unit.
Tooth is sickle-shaped
Blades with a concave tooth shape are convenient for cutting material in cross-cutting direction relative to the arrangement of fibers.
- The movement of the workpiece on the work table when cutting occurs with great physical force;
- Cracks and chips are observed along the cutting line;
- Engine overheating occurs during operation;
- There is a burning smell in the air;
- Material burns, resulting in dark spots along the kerf.
If you notice any of these signs, you must sharpen circular saws with your own hands immediately. You can also check the sharpness of the saw either by feeling or by sight with a magnifying glass. The allowable cutting-angle rounding radius must be set at 0.1-0.2 mm. When cutting large workpieces, all cutting edges wear out.
Sharpening with a machine tool
If there is an opportunity to purchase a special machine, then the process under consideration can be carried out with the maximum efficiency index. This machine is compact and can be used at home.
Particular attention is paid to the choice of abrasive wheel. In this case, note the nuances below:
- It is hard to sharpen a carbide disc.
- When choosing, one should pay attention to grinding wheels made of elbor, with diamond grit or with green silicon carbide.
Enkor Korvet 472
Electric lathe SZTP 600T
JMY8-70 electric machine
The sharpening process with professional equipment is very simple. The disk is fastened by means of a special locking device. It is designed with the design features of the wheel in mind. Let us pay special attention to the fact that with the use of special machines it is very easy to conduct sharpening of circular saws with the maintenance of the necessary indicators. Maximum inaccuracy is minimal. This is due to the fact that the design features a special angle gauge. In order not to make a mistake at the time of work which teeth have already been machined, mark the starting point with a marker.
Professional equipment from 150 000. up to 1.5 mln
Professional sharpening machines are intended for use in the repair department of large sawmills or by service companies specializing in this type of tool. All are equipped with industrial controllers with the ability to select the processing program for a specific saw blade model.
| № | Model | Max. diameter (mm) | Drive power (W) | Weight (kg) | Type of control | Price (.) |
| 1 | MF1263 | 630 | 300 | 260 | automat | 165 000 |
| 2 | Unimac 600A 288 000 | 630 | 300 | 250 | automatic | 288 000 |
| 3 | GRIGGIO GA U5 | 400 | 560 | 115 | n/a machine | 451 000 |
| 4 | OS-2M | 1500 | 1 100 | 270 | n/a machine | 525 000 |
| 5 | OTOMAT-96 | 750 | 1 000 | 850 | automatic machine | 1 500 000 |
Tools required
With their own hands circular saw blades can be sharpened only with special tools. There is also a machine that allows you to automate the process, making it more efficient.
The tools listed below can be used to do the job of sharpening the circular saw blade with your own hands:
You can also use a circular saw blade sharpening machine, which does not need the above tools.
When it is necessary to carry out work on the restoration of circular saws?
Quite an important issue can be called to determine when to sharpen circular saws. Severe wear and tear can make this work impossible. We can distinguish three clear signals that determine the need to sharpen the circular saw blade:
- Smoke formation, the protective cover gets hot. The fixture usually has a special protective cover, which can get hot if the disc is blunt. Also note that in special cases, smoke may be produced due to excessive heating of the cutting zone.
- Also with mechanical feeding, when the pressure is regulated by your own hands, you should give a lot of force to get the desired result.
- Wood or other material is smudged and smells in the cutting area.
Sharpening of circular saw blade is recommended in the above situations.