Do-it-yourself circular saw repair

In detail: DIY repair of a circular saw from a real master for the site my.housecope.com.

A circular saw is an indispensable tool for building a house and maintaining a subsidiary farm. Even if all the rules and regulations of use are observed, the saw, like any mechanism, can fail. To fix a malfunction yourself, you need to know how the tool works and how to correctly diagnose a broken part.

A circular saw in terms of its design does not fundamentally differ from other electrical appliances (household or construction tools).

Its main parts are:

Frame
Electric motor
Power cord and plug.

The main difference between the saw and other tools lies in the presence of a saw blade, to which the torque is transmitted from the electric motor when the power button is pressed.

The armature is a copper winding that conducts current, and a magnetic circuit in which a rotary shaft is installed. On one side of the armature there is a gear, and on the other, a collector with lamellas. The magnetic circuit consists of lacquered plates and grooves isolated from each other.

The rotor is a steel shaft, on which a core with machined, equidistant grooves is located, in which the armature winding is laid.

The stator is made of electrical steel with a high magnetic permeability coefficient. This element is rigidly fixed in the saw body. It has the shape of a cylinder with grooves in which the stator windings fit.

In most cases, collector-type electric motors are installed on circular saws for wood. It includes the above elements: armature, rotor, stator.

Video (click to play).

The shaft is a metal rod that transmits torque from the motor to the saw blade flange using bearings.

Repairing a tool begins with determining the cause of the breakdown. If smoke escapes from the tool during operation, this indicates engine failure. If, however, a noise or whistling occurs during the operation of the saw, this indicates a mechanical malfunction.

There are times when the tool simply does not turn on without any signs of breakage. In this case, first of all, you need to check the integrity of the wire supplying electricity and contact brushes. Since the brushes energize the moving parts, they are susceptible to grinding and can wear out over time to such an extent that the saw will not work. It happens that the contact of the brushes with the stator terminals is broken or oxidized.

To repair the electric motor, it is necessary to disassemble the tool. This must be done sequentially, remembering the order of the removed parts. You can prepare an electric saw connection diagram. This is necessary for the subsequent correct assembly.
Typically, engine breakdowns are associated with manifold problems. Removing it is not so easy. This must be done safely for the armature bearing. You need to use a sharp instrument. Having inserted it into a special groove, you need to gently hammer it with a hammer until the shaft moves.

Then the anchor is removed from which carbon deposits are removed. If it is badly worn out, a complete replacement of the part is required. After that, the contacts of the collector windings are cleaned, if necessary, they are changed.

In order to avoid damage to your instrument, you should carefully handle, transport and store it. Most breakdowns occur as a result of working with a dull saw blade or in the absence of lubrication in the parts, and this leads to overloading of all elements of the saw and equipment failure.

Home »Circular Saw Repair Do It Yourself

In Russian saws, sintered tungsten-cobalt alloys of grades VK (VK6, VK15, etc.) are used as the material for cutting blades. The number means the percentage of cobalt. Do-it-yourself guide rail for a hand-held tire. Circular saws for. BK6 has a hardness of 88.5 HRA, BK15. 86 HRA. Foreign manufacturers use their own alloys. Carbide VK alloys consist mainly of cobalt cemented tungsten carbide. The properties of the alloy depend not only on its chemical composition, but also on the grain size of the carbide phase. The smaller the grain, the higher the hardness and strength of the alloy.

Strengthen the carbide plates to the disc by high-temperature brazing. As a material for soldering, in the best case, silver solders are used (PSr-40, PSr-45), in the worst case. copper-zinc solders (L-63, MNMTs-68-4-2).

The following types of teeth are distinguished by shape.

Straight tooth... Typically used in rip saws where quality is not critical.

Oblique (beveled) tooth with left and right angles of inclination of the rear plane. Teeth with different angles of inclination alternate with each other, which is why they are called alternately cut. This is the most common tooth shape. Depending on the size of the sharpening angles, saws with alternating cut teeth are used for sawing a wide variety of materials (wood, chipboard, plastics). both in the longitudinal and transverse directions. Sharpening circular saws with your own hands: principles and angles of sharpening. Saws with a large backplane tilt angle are used as scoring saws when cutting double-sided lamination boards. Their use allows you to avoid coating chips at the edges of the cut. Increasing the bevel angle reduces the cutting force and reduces the risk of chipping, but at the same time reduces the tool life and strength of the tooth.

The teeth can have an inclination not only of the rear, but also of the front plane.

Trapezoidal tooth... Sharpening circular saws with your own hands: angles, methods. A feature of these teeth is the relatively slow speed of blunting of the cutting edges in comparison with alternating beveled teeth. They are usually used in combination with a straight tooth.

Alternating with the latter and slightly rising above it, the trapezoidal tooth performs a rough cut, and the straight one following it. fine. Saws with alternating straight and trapezoidal teeth are used for cutting boards with double-sided lamination (chipboard, MDF, etc.), as well as for sawing plastics.

Tapered tooth... Tapered saws are auxiliary and are used to cut the lower layer of the laminate, preventing it from chipping when the main saw passes.

In the overwhelming majority of cases, the front edge of the teeth is flat, but there are saws with a concave front edge. They are used for fine cross cuts.

The sharpening angles are determined by the purpose of the saw. those. the kind of material for cutting and in which direction it is intended. Rip saws have a relatively large rake angle (15 ° -25 °). Sharpening circular saws at home. You can sharpen the saw with your own hands without using a special sharpening machine, which is of great cost and is used. For cross-cut saws, the angle γ usually ranges from 5-10 °. Versatile cross and rip saws have an average rake angle. usually 15 °.

The quantities sharpening angles are determined not only by the direction of the cut, but also by the hardness of the material being cut. The higher the hardness, the smaller the front and back angles should be (less sharpening of the tooth).

The rake angle can be not only positive, but also negative. Saws with this angle are used for cutting non-ferrous metals and plastics.

When sawing massive workpieces, the side edges are also subject to rapid wear.

The saw should not be excessively blunt.The radius of rounding of the cutting edge should not exceed 0.1-0.2 mm. In addition to the fact that when working with a very blunt saw, productivity drops sharply, sharpening it takes several times longer than sharpening a saw with a normal bluntness. The degree of bluntness can be determined both by the teeth themselves and by the type of cut they leave.

Correct sharpening of circular saws consists in ensuring the maximum number of sharpenings, which in the optimal case can reach 25-30 times, while ensuring the proper sharpness of the cutting edge. For this purpose, it is recommended to sharpen the carbide tooth along the front and rear planes. Spare parts for circular saws the thickness of the elements of the tire; floors for giving with your own hands; In fact, teeth can be sharpened one at a time. front plane, but at the same time the number of possible sharpening turns out to be almost two times less than when sharpening along two planes. General information on how to properly sharpen circular saws with your own hands. The figure below illustrates why this is happening.

Last sharpening pass saw blades it is recommended to do it along the posterior plane of the tooth. Standard metal removal rate. 0.05-0.15 mm.

Before sharpening, the saw must be free of dirt, such as resin, and the values of the sharpening angles must be checked. On some saws, they are written on the disc.

When using abrasive wheels (especially diamond), it is desirable to cool them with coolant.

As the temperature rises, the microhardness of abrasive materials decreases. An increase in temperature to 1000 ° C reduces the microhardness by almost 2-2.5 times compared to the microhardness at room temperature. An increase in temperature to 1300 ° C causes a decrease in the hardness of abrasive materials by almost 4-6 times.

Repair Chinese instrument is not always cheap sometimes it is easier to buy a new one than to repair an old one This

Circular saw device with separate motor.

For all models, it is located in the handle, which, when untwisted, diverges into two parts.

It cannot be halved to the end, it will hold on to other parts, but you can already get to the button, but it will be a little inconvenient. Despite this, it is necessary to check the functionality of the switch with the tester probes.

If it turns out to be faulty, the repair is complete. However, in order to replace the new one, the saw will have to be disassembled completely. But if the button is working, you will have to do this too.

Remove the disc. Now you can remove the protection, which is what you are doing. There are 4 long bolts under it, unscrew them. The sequence and number of parts may be slightly different, but in the end, the motor should remain in the hands with a gearbox, a handle and an electrical cord. Disconnect the gearbox, and then it's time to remember how the malfunction manifested itself.

Symptoms of such malfunctions can manifest themselves in different ways, but almost always the work is accompanied by extraneous noise. It can be whistles, rattles, or clicks. Now, while the motor and gearbox are still assembled, it is necessary to establish which of them is faulty. Try to twist the motor by the shaft. It should rotate quite hard, but evenly, i.e. should not wedge.

Circular saw layout.

If the motor shaft does not rotate or jerks, the motor is defective. Disassemble it and watch the bearings. The first one stands in the engine housing, the other on its rotor. We can confidently assume that one of them is to blame. It would be nice to have the first one, it is quite easy to change it.

If the bearing on the engine anchor is to blame, you can safely carry it for repair. It is almost impossible to remove it yourself without a special device. In addition, any attempt to do so may damage the armature. You will not have to carry the entire saw to the workshop, but only the rotor. It is easier and cheaper.

The main malfunction of the gearbox is the wear of the gear teeth. In this case, it must be replaced. You should also pay attention to the splines of the anchor. They shouldn't be damaged either.

These faults are the most common. During operation, a strong sparking occurs unexpectedly in the brush area. Smoke may emit and a burning smell may be felt. Such damage is sometimes very difficult to diagnose. Let's start with the simplest and most expensive case.

Circular saw performance check diagram.

After opening the engine, it turns out that there are traces of burning both on the rotor and on the stator. Everything is clear here. Both must be changed. The option is expensive, but the possibility of error is excluded. Worse when the stator is smoked and the armature is as good as new. At first glance, it seems simple - you need to change the stator. Not at all necessary. The rotor may also be faulty, but be “in the open”. Moreover, he could have caused a more serious breakdown. Determining its malfunction in this case is quite simple.

Disconnect the stator terminals from the brushes. In their place, fix the tester probes, it should show a small resistance.
Slowly rotate the motor shaft, if at some point the resistance increases, then the armature is faulty.

And the last, the most difficult case, when visually everything is in order. Even if you apply the method described above, this will not guarantee that the rotor is working properly. However, if the device shows an open circuit, then you can try to change it. Basically, in this case, it is better to contact the master. You can't do without special devices.

Very often, a circular saw is bought for a specific purpose. At the same time, the person does not even think about whether she is suitable for this. The fact is that there are professional circulars designed for long-term work, and there are those that can work only 3 hours a day, and even then with interruptions.Of course, if you work with such a saw without interruption all day, it will definitely burn out. After all, no manufacturer hides what operating mode is provided for a given saw. As a rule, nobody is interested in this. In addition, many, having bought a saw in a store and noticing that she has a disc with victorious solders, decides that it does not need to be sharpened. The result is smoke from the engine. Even such a disk becomes dull over time. The performance of the saw drops dramatically, and you demand the same return from it as before. So she can't stand it.