DIY punch repair

Recommendation points

• How the puncher works
• Identifying engine faults
• Replacing the button and brushes
• How to replace bearings yourself
• Chuck malfunctions
• Repair of gearbox and impact mechanism
• Barrel punchers
• Pistol perforators
• Raster coupling

If the warranty period for the hammer drill has expired, you will have to do it yourself. As a rule, actions are reduced to replacing faulty parts, and today we will talk about typical breakdowns, selection of components and do-it-yourself repairs.

How the puncher works

The perforator can be classified as a tool with a device of increased complexity. However, a consistent consideration of the details and principle of operation will help a thorough understanding of the nuances of the mechanism and troubleshooting..

The source of motion, as in many other construction tools, in the hammer drill is a single-phase motor with a phase rotor. We will consider it separately, and now we will take the gear set on the front armature shaft as the starting point. It is she who sets the rotation for all other elements of the system..

Barrel puncher device: 1 – power cord; 2 – carbon brushes; 3 – electric motor; 4 – switch; 5 – eccentric mechanism; 6 – impact mechanism; 7 – quick-change cartridge

In a drum rock drill, the motor and pinion are vertical. The key difference from the pistol-type tool here is the presence of an intermediate gear. There is nothing tricky in its device: a flat gear from the engine rotates two others with different gear ratios. One of them transmits rotation to the main shaft, the other turns the eccentric shaft with a connecting rod, which provides a reciprocating movement of the percussion mechanism.

In horizontal (pistol) type perforators, there is no transfer gearbox as such, the rotation is immediately transmitted to the intermediate shaft located below the axis of the main spindle. This shaft is seated on two bearings, between them there is a “drunk bearing”, which oscillates during rotation and drives the piston of the striker. On the protruding front end of the shaft there is a gear, due to which rotation is transmitted to the barrel.

Pistol-type perforator device: 1 – switch; 2 – electric motor; 3 – brushes; 4 – “drunk bearing”; 5 – “flying” piston; 6 – striker; 7 – SDS quick-release chuck

Any hammer drill has mode switches. In the barrel, they simply lift the gears of the transfer case, disengaging them. In a pistol gun, one of two control schemes can be used. In the simplest case, one switch shifts the intermediate shaft, which, being pushed as far forward as possible, meshes with the chuck gear, but at the same time the clutch for transferring rotation to the swing bearing is disengaged. In the middle position, both mechanisms are included in the transmission, and in the maximum recessed position only the drummer works. The obsolete kinematic diagram has two switches, one of which disengages the rocking bearing clutch, and the other shifts the intermediate shaft.

Identifying engine faults

If the rotary hammer motor has a factory defect, the latter manifests itself in the very first months of operation. Otherwise, the cause of the breakdown is often a violation of the operating technique or the extreme wear of the components..

The main element of the motor section, subject to intense wear, is the graphite brushes, which transmit current to the rotor windings. When the brushes are erased, their clamping weakens, due to which the gap between the graphite and the armature lamellae increases, and intense sparking occurs. By sound, this malfunction cannot be confused with anything: when turned on, a strained hum is heard, the collector sprays with a sheaf of sparks, the rear of the engine is intensely heated.

The motor windings are made with a wire in varnish insulation, which loses its dielectric properties from overheating, cracks and crumbles. Small short circuits between adjacent turns can be identified by the characteristic hum of the engine during operation. Unfortunately, it is almost impossible to rewind the stator and armature at home, but most of the engine parts are typical and it is easy for them to find a replacement..

Bearings are other vulnerable parts. There are two of them at the anchor: the rear one is fixed in the housing of the electrical part inside the vibration-damping cap, the front one is inserted into the seat of the gearbox housing or screwed to it with a cap. Bearing wear is easy to determine: when rotating by hand, their course is either too free with a characteristic rustling, or there are wedges, backlash and extraneous noise. The bearings have a closed cage and are not designed for maintenance. It is much easier to replace them with new ones, it is enough to rewrite the number on the separator cover or the end of the outer cage.

Replacing the button and brushes

During the operation of a high-quality punch, the button may have to be changed more than once. It is optimal if you purchase a button in advance for a specific model. If you need to remove the defective part for a sample, sketch on paper a wiring diagram showing the color coding of the wires. Some of the buttons have screw clamps and you need a narrow slotted screwdriver to unscrew them. Some buttons are equipped with spring-type clamps, in order to release them, you need to drive the awl into the hole next to the wire entry. It is quite rare to find disposable spring clips, the wires from which are not disconnected. The veins from the old button will have to be cut, cleaned and tinned, and then connected to the new button in accordance with the connection diagram.

It is quite easy to change the brushes in the hammer drill, the channels for them in some models are brought out and closed with plugs for access without disassembling the tool. Otherwise, you just have to remove the housing of the electric motor part of the tool and carefully inspect the manifold assembly. The seats of the brushes are located inside or near the plastic racks holding the rear bearing plug, two wires go to them. The mechanism for attaching and pressing the brushes varies from model to model.

In most cases, removing the brushes requires only pulling out two metal tabs with pliers, unscrewing a couple of screws or unfastening the springs of the clips. During periodic inspection of the brushes, it is recommended to remove and check for chips, clean the seating grooves from dust and dirt. Be careful not to confuse the left brush with the right one; observe their original position when installing. As a rule, brushes are lapped at an individual angle, a change in which either requires lapping again or leads to the destruction of the graphite element..

When replacing worn-out brushes, it is only important to select the correct size and cross-section, and then grind the brushes in after running the engine for 2-3 minutes without load in no impact mode. Now almost every hammer drill is equipped with a set of interchangeable brushes, but a replacement can also be found by the remains of those that have already worked.

How to replace bearings yourself

The hammer drill contains from five to ten radial rolling bearings of various sizes and the need to replace them is only a matter of time. It is very important to periodically disassemble and assess the degree of wear of these units, otherwise more serious malfunctions may develop in the future..

Almost every bearing in the hammer drill is easy to remove, the fitting dimensions for them are selected with high accuracy. In some cases, the retaining ring may interfere with removal. If it is not there, and the bearing refuses to be removed, a universal two-grip puller is used. If a puller is not available, then the part on which the bearing is seated must be clamped in the soft jaws of a vice, and then knock down the worn out element by striking through the adapter on the inner ring.

When seating a new bearing, do not subject it to direct hard impacts. You should use an elastic support, for example, a cut of a polypropylene pipe. It must first be cut obliquely so that the impact force falls exclusively on the inner clip. This prevents the rolling elements from leaving microscopic dents on the grooves..

Chuck malfunctions

The SDS chuck consists of a nipple with one or two holes in which balls are seated, usually with a diameter of 6.7 mm. The balls move freely in the holes while the plastic cartridge body is pulled back, in the normal position they are tightly pressed by a spring through a massive steel ring.

To disassemble the cartridge, you need to pry the front boot with a screwdriver and remove the retaining ring from the fitting. The rest of the parts are simply put on the fitting and can be removed without additional manipulations, it is only important to put them back in place in the correct order.

As a rule, the main cause of chuck malfunction is worn-out balls or a squeezed plate and pressure ring. Because of this, the rig either does not hold at all, or flies out during operation. You can get such balls in any quantity by breaking bearing number 106. The bore holes and splines inside the bushing have a much longer resource, but if the replacement did not give the expected result, you will have to change the fitting only assembled with the barrel.

Please note that the rapid wear of the chuck parts occurs due to the loose sealing of the anthers, both front and annular on the fitting. Drill shanks should always be kept lubricated and a special dust washer should be used when drilling the ceiling.

Repair of gearbox and impact mechanism

So we got to the most meaningful part of our instructions. Due to the differences in the structure of the transmission part and the shock pulse generator in different families of perforators, their maintenance and repair are carried out according to different schemes..

Barrel punchers

The drive gear of the transfer case is seated on the motor bearing, the other two have their own stops. They need to be periodically checked for jamming and backlash, changed if necessary..

The connecting rod mechanism has its own bearing, which is usually seated on the cam of the eccentric wheel, sometimes at the base of the connecting rod itself. Occasionally, a sleeve bearing is used in this place, which requires constant availability of grease with a normalized viscosity index. The wear of this assembly often requires replacing the eccentric barrel and connecting rod..

The transmission of rotation is carried out by a straight or bevel gear, in this place the constant presence of lubricant is also important. The need for replacement is determined by blackening, thinning and the presence of shiny inclusions.

Pistol perforators

In rock drills with a horizontal rotor, problems can arise from wear or seized bearings. This is the most dangerous malfunction for all hammer drill units: fragments of a broken bearing can get into the parts of the impact mechanism and disable them..

The countershaft and drunken bearing are often seated individually. For complete disassembly, unscrew the clamping bracket of the front end of the shaft, disconnect the switch lever.

A typical breakdown of a horizontal gearbox is wear of the gear wheels. In the absence of a press, removing them will not be an easy task, it is much easier to break them by making a couple of cuts up to 2/3 of the thickness. The new gear is pressed in after preheating to 150-200? C, this can be done with a building hair dryer or in the oven.

All gearbox types should be thoroughly cleaned and relubricated periodically. After disassembly, all parts are thoroughly washed in kerosene, getting rid of fragments of broken elements and metal shavings. After that, a special type of grease is applied to all moving parts..

Raster coupling

The barrel of hammer drills of almost all types has the same structure. The outer sleeve of the clutch is supported by a needle bearing at the front of the gear housing. On the outer side of the glass, the main gear wheel for transferring rotation is fixed together with a safety clutch. To remove them, you need to remove the retaining ring, compressing the spring beforehand with adjustable pliers.

It is also easy to disassemble the insides of the grid sleeve. They are fixed with a retaining ring, which is removed through a pair of side holes with a conventional screwdriver. When the ring is removed, the parts inside can be extruded by inserting a screwdriver from the front of the barrel.

Inside there is a “flying” impact bolt and industrial mass – a shock force receiver. Most bolts are assembled and often wear out rubber gaskets and packing rings. It is recommended to change these elements at every service. The bolt itself and the industrial mass can be cracked due to fatigue during prolonged use. These elements cost mere pennies and at the slightest traces of flaring, it is also better to replace them immediately..

It is difficult to give more specific recommendations for the repair of the raster coupling and the reduction gear part: each manufacturer’s kinematic diagrams may have slight differences. Nevertheless, most of the faults are clearly visible during inspection and revision. In this regard, it is recommended to save the assembly diagram from the instructions for the tool, it should also be used when searching for components, which are determined by the serial number of the list of used parts.