DIY punch repair and maintenance

Recommendation points

• Electrical faults
• Engine problems
• Gearbox and barrel breakage
• Cartridge replacement and repair
• Fixing problems with switches
• Tool maintenance

For many repairmen, a hammer drill is the main working tool and its failure becomes a real tragedy. So that the work does not stand, you should learn how to properly maintain the hammer drill and be able to do minor repairs with your own hands right at the workplace.

Electrical faults

The mechanics of the hammer drill has a rather complex device, which cannot be said about the electrical circuit. Nevertheless, breakdowns in the power supply circuit can be attributed to the most common. Their diagnosis is carried out according to a number of signs:

1. Lack of rotation or interruptions in operation are most often the result of a broken power cord. Move the wire in different directions while keeping the power button pressed, especially in the area of ​​the plug and the entrance to the housing.
2. The punch turns on / off at random at different degrees of pressing the button. The latter, with such signs, is recognized as faulty and must be replaced..
3. When turned on, humming noise and arcing are observed in the engine manifold. The reason for this is wear or premature destruction of the brushes or wear of the contact blades..
4. Increased arcing without hum can cause a capacitor malfunction, which can also be accompanied by overheating of the manifold assembly..

On close acquaintance, the power circuit of the hammer drill turns out to be typical for most types of power tools. To access it, you only need to disassemble the plastic handle into two halves, but be careful and immediately mark the seats of the parts and the layout of the veins. All parts of the electrical circuit – buttons, capacitor, terminals – can be replaced and therefore they are usually not repaired.

Engine problems

The hammer drill motor also has a typical device and is not much different from most single-phase collector electric motors for power tools. The engine stator does not deserve special attention and fails quite rarely. The only thing worth mentioning is that in some models the stator is rigidly fixed in the housing glass, and to inspect the engine, you will have to disassemble both the tail section with brush pockets and the front connection unit with the gearbox.

On one side of the rotor shaft, the drive gear of the reducer is fixed, followed by a bearing and a cooling impeller, a magnetic circuit with windings, a collector current collector and one more bearing. The most vulnerable parts of this unit are bearings, which are mostly maintenance-free and have a short life due to high speed operation. Their wear is accompanied by the appearance of extraneous noise during operation, vibration and heating of seats. To replace the bearings, you need to pull off the ends of the shaft using a puller or a slingshot mandrel, and then install new ones, preheating them with a hairdryer. Remember to replace the spacers and o-rings in the correct position.

Another element of the armature that often fails is the impeller. The ingress of large stones through the air intake causes the blades to break off, and sometimes to their complete destruction. In this case, debris and debris fall into the motor, scratch the varnish on the wires of the windings, and the lack of normal blowing leads to permanent overheating of both parts of the engine. For some motors it is possible to remove and press on a new impeller, but most armatures have to be replaced as an assembly. This is partly reasonable, because without normal cooling, the anchor remains viable for a few minutes..

Damage to the insulation of the windings can cause a short circuit between the turns, which leads to a change in resistance and uneven operation of the motor. You can measure the stator resistance using two output conductors, it should be equal to the passport value. Measurements of the armature windings are carried out between two lamellas, while the values ​​may deviate slightly from the passport data, but all windings must have equivalent conductivity.

The short-circuits of the windings can be easily identified by the characteristic blackening of the varnish in places of overheating and burning. Black varnish no longer serves as an insulator; such an engine must be replaced immediately. Basically, the maintenance of the electric motor comes down to blowing it out of dust, as thoroughly as possible, and cleaning the collector from graphite dust and carbon deposits.

Gearbox and barrel breakage

Problems associated with the rotation of the chuck and interruptions in the operation of the percussion mechanism are usually located in the gear section of the rock drill. Depending on the location of the engine, the design and principle of operation of this unit may vary. Common to both types of structures is the presence of a raster sleeve (barrel), in which a pneumatic percussion mechanism is located. To access service, it is necessary to remove the upper rotation mode switch and unscrew the front gear part of the tool from the motor part, usually the fastening is made on four powerful screws. Sometimes it is necessary to remove the plastic covers first. After that, the raster sleeve is knocked out of the metal housing of the gearbox with a rubber hammer..

In rotary hammers with a horizontal rotor position, rotation is transmitted due to a toothed gear fixed around the circumference of the barrel and receiving force through a ratchet mechanism compressed by a spring (safety clutch). Here, the difference in the device for different types of perforators lies in the shape of the drive gear: for horizontal ones it is longitudinally helical and fixed on the armature shaft, for vertical ones it is conical, serving as the output of the transfer-reduction gear mounted above the engine. The driven gear differs only in the direction of the teeth.

The most obvious differences are the striking mechanism. The transmission of rotary motion to translational motion in barrel rock drills is due to a crank mechanism driven by an intermediate gear. In the case of horizontal rods, everything is somewhat simpler, a swinging (drunk) bearing with an additional shaft mounted on two rolling bearings works here. The piston part has a not too complicated device: a piston-striker moves inside the outer sleeve of the sleeve, in the front part there is a so-called industrial mass – a striker catcher. Sometimes the last two elements are telescopic with a ball-groove fit, which works in a similar way to the SDS chuck. Almost always, to disassemble the barrel, you need to remove the retaining ring, which is tightly set inside the outer barrel glass, prying it through the side hole.

Maintenance of the gear-piston part includes complete disassembly, flushing from dirt and metal shavings in kerosene, and changing the lubricant. Drum rock drills have a crank cover for additional lubrication. Both types of mechanisms are very susceptible to clogging and wear on the rolling elements. The situation can be aggravated by aging of the piston mechanism O-rings, which causes dust particles from the cartridge to penetrate into the sleeve. Please note that the gear part contains many small parts and the revision must be carried out, adhering to the assembly diagram, which is indicated in the passport documentation of the tool.

Cartridge replacement and repair

Failure of the SDS chuck is usually expressed either in the inability to insert the drill shank, or in its protrusion during operation. The fixing mechanism is ridiculously simple and you can literally fix most of the breakdowns on your knee.

To disassemble the cartridge, you need to tuck and remove the rubber boot in the front of it. Pulling the glass towards you, as when inserting the drill, remove the retaining ring from the barrel fitting and remove the crimp sleeve together with the spring. Do not forget to carefully remove two small balls from the grooves..

The tapered inside of the nozzle presses the balls into the grooves when the drill is to be fixed and allows them to move freely when the nozzle is pulled back. As a rule, the cause of the spontaneous departure of the drill is the grinding of the balls or the inner surface of the sleeve. Replacement parts can be taken assembled with a new chuck, balls for SDS-Plus are 6.9 mm in diameter and can be removed from a normal bearing.

Jamming and the inability to insert the drill can also be the result of grinding off parts, but often this leads to coking of the cartridge with dried grease or the ingress of foreign objects. In any case, further operation of the tool in this state leads to the breaking of the seating grooves already on the shanks of the drills, and the above-described problems may continue to occur even with a fully functional chuck. The cause of most breakdowns is immediately visible during disassembly and cleaning..

Fixing problems with switches

Drum rock drills have two switches for striking and rotating modes. In “verticals” there can also be two of them, or both are combined on the left side of the body with a three-position handle.

The process of removing plastic handwheels from the switches can be very simple and consist in unscrewing one or two fixing screws, or the procedure is more complicated and is described in the instructions for use and repair.

The reason for unauthorized switching is usually a lack of fixation due to a broken spring or an insufficiently tight fit of the handle. If the mode switch wedges, this may be due to grinding of parts of eccentric or rotary mechanisms. Remove the handle and try to move the roller or gear by hand with a screwdriver. If it does not work, then the switching mechanism is working, and the cause of the malfunction is a foreign object in the gearbox.

Tool maintenance

Let’s summarize and outline the main steps for caring for a hammer drill and keeping it in good condition..

First of all, lubrication. In some models, you can replenish its stocks without disassembling the case through the holes of the mode switches. For barrel rock drills, there is a special cover in the front for this, but through it you can only lubricate the crank mechanism and the intermediate gear.

Bore and hammer lubrication almost always requires detailed disassembly and flushing. The presence of solid particles in this mechanism leads to rapid wear, seizure of the piston, and biting of the stuffing box seals. It is also necessary to lubricate the drill shanks with thick grease and keep them always clean and lubricated, this will significantly extend the life of the chuck..

Like any other tool, the hammer drill does not like dust. Therefore, when working on the air intake slots, it is better to pull on a nylon stocking or other improvised filter. But even with such precautions, you should periodically disassemble the motor part and thoroughly blow it through, because even the slightest layer of dust on the windings greatly impairs heat dissipation..