DIY Hitachi circular saw repair

The advantages of any home instrument can be fully appreciated only after it fails. This axiom is known to every home craftsman. The presence in the arsenal of a large number of devices has led to the fact that most people simply cannot imagine how to do this or that operation without them.

The circular saw is used to cut evenly on a variety of materials.

This is especially true in the case of a circular saw. The fact is that it is indispensable for longitudinal sawing of wood; it has no worthy analogue among hand tools. This cannot be done with a conventional hand saw. Therefore, when the circular for some reason refuses to work, all work stops. Something needs to be done urgently. However, do not rush to carry it to the workshop, it is quite possible to repair the circular saw yourself.

The first step is trying to determine what is broken. This does not mean a specific node, but the nature of the damage. It can be mechanical or occur in the electrical part of the saw. In other words, if smoke came out of it, this is one thing, but when extraneous noise or whistling appears, this is completely different. It is these two criteria that are the main ones when localizing a malfunction. There is, however, a third, when the saw makes no sounds at all. Let's start with him.

Circular saw device.

Ironically, the fact that the saw is silent can be a good sign. Here it is not superfluous to mention those faults that are usually printed on the last page of the operation manual. At first glance, they seem ridiculous, but show them a little respect. Check to see if the outlet is energized and the power cord is working. If everything is fine, then there is only one chance to avoid a complete disassembly - to check the brushes.

Video (click to play).

On the vast majority of circulars, in order to get to the brushes, you need to unscrew two bolts. This assembly consists of two carbon elements that abut against the manifold. Since it constantly rotates, the brushes are subject to wear and tear and over time "freeze", i. E. do not reach him. This is the first thing to pay attention to. In addition, the carbon brushes are connected to the stator terminals. At this point, contact sometimes disappears. Check it. If everything is fine, disassembly cannot be avoided.

The operation itself is quite complicated, some workshops take money for it, regardless of the result of the repair. Each saw has its own design, and precise advice cannot be given. You can figure it out on your own. But what to disassemble in the first place, let's take a closer look.

A very common damage, regardless of brand, is a faulty switch button.

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 with a gearbox, a handle and an electrical cord should remain in your hands.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.

1. Disconnect the stator terminals from the brushes. In their place, fix the tester probes, it should show a small resistance.
2. 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.