A power drill is one of the most common tools in the household. And it is very bad when it suddenly stops working. In such cases, I really want to repair the drill with my own hands.
Diagram of the device electric drill.
The design of the drill or punch is quite simple. Different models of tools mainly differ only in the difference in the layout of parts and the quality of their manufacture. The versatility of the principle of operation and structures used makes it possible to repair the drill in most cases of malfunctions.
Design features of the drill
Any electric drill consists of a housing in which an electrical and mechanical part is placed, and a cartridge in which the drill is mounted, on the main shaft of the drill. The electrical part usually contains:
- electric motor;
- contact brushes fixed in the brush holder;
- start button (switch);
- engine speed control;
- reverse device;
- starting capacitor;
- power cord (cable).
Diagram of the percussion mechanism of the drill.
In turn, the two-phase AC motor consists of a stator and a rotor (anchor) with a collector.
The mechanical part includes a gearbox and bearing system. The gearbox transmits the rotation of the electric motor to the drill shaft, reducing the speed of rotation. More complicated mechanical part in a hammer drill (perforator). The perforator gearbox provides shock, translational and rotational movement to the drill bit (borax). In addition to the gear, its design includes pistons (impact and flying), a ram and a head.Back to table of contents
Types of faults electrical and mechanical parts of the drill
Malfunction of the electrical part is manifested in the form of the absence of rotation of the engine, i.e. when there is no indication of engine starting (humming, vibration, etc.). If the hammer drill does not turn on, and the chuck is easily rotated by hand, then we can safely talk about the malfunction of the electrical part. The same can be argued if there is no speed adjustment or reverse rotation. About the expected malfunction in the electrical part says arcing during operation of the drill. Temporary interruptions in the work of the drill, extraneous noise can also indicate an electrical circuit.
The most common fault in the electrical part is due to the wear of the contact brushes. If they sharpened by 40%, then arcing and malfunctions can be observed. With more wear brushes the motor simply does not turn on. The procedure for determining the fault in the electrical part is recommended as follows (as far as availability). Initially, the tester determines the integrity of the cord (cable). Then the operation of the start button (switch) and the integrity of the starting capacitor are checked. Then the contact buttons are removed and checked. At the end, the integrity of the motor windings is determined.
Scheme drill chuck.
A clear sign of a fault in the mechanical part is jamming of the drill shaft. If the cartridge does not manage to scroll by hand, and at the same time you hear a hum of the electric motor when it is turned on, then the reason lies in the breakdown of the gearbox or bearing. The most common cause of failure in the mechanical part is the destruction of the support bearings. Breakage of the gearbox may also appear in the case when the cartridge is rotated by hand and the electric motor is running and rotation is not transmitted to the main shaft. A fault in the mechanical part can cause intermittent failures (temporary stop) of the drill, humming, gnashing and insufficient speed of rotation of the shaft. In perforators, a fault in the mechanical part can remove the shock movement of the drill.
Finally, a malfunction may occur in the drill chuck. Thus, it may be difficult to remove the drill when the cams do not break due to a breakage in the gearing inside the cartridge. Sometimes the malfunction is manifested in the form of scrolling the cartridge relative to the shaft of the drill. In this case, the fault occurred in the area of attachment of the cartridge to the shaft.Back to table of contents
Repair of the drill: replacement of contact brushes
One of the most common causes of a malfunction is the wear or burning of the contact brushes. The first signs of wear of the brushes manifest themselves in the form of sparking in the zone of contact between the brushes and the armature of the electric motor and minor disruptions in the work of the drill with increasing load.
The location of the contact brushes inside the drill.
In many drill models, access to the brushes is simplified, and changing them is not difficult, and some drills require disassembling the case and removing the brush holder. Brushes must be replaced with new ones, equal in size to the failed brushes.
They should be firmly fixed in the brush holder. The electrical contact of the lead wire must be well tightened. The contact of the brush with the collector armature must be reliable. It is necessary to check the action of the spring.Back to table of contents
The failure of the electric motor is the second largest cause of the drill malfunction. This is due to damage to the stator winding or anchor. Such damage occurs due to a factory defect in the windings or improper operation of the drill (long work without interruptions, the load is above the allowable when jamming the drill, etc.). As a rule, electrical breakdown of the winding is easily determined visually or by the characteristic smell of burning. If there are no visible manifestations, the motor windings should be checked with a tester, ohmmeter and megohmmeter according to the resistance value. There may be three types of damage to the wire - a short circuit between the coils, breakdown of the coil on the housing or wire breakage. Repair of the stator or anchor is not carried out independently
Connection diagram of the motor drill.
To replace the elements of the electric motor, the drill casing is disassembled, the contact brushes and lead wires are disconnected, and the electric motor is removed together with the supporting bearings.
If necessary, drive the gear. The faulty element of the electric motor is disconnected and replaced with a new one or installed after the repair (rewinding) by professionals.Back to table of contents
Inspection of electrical components
The switch (start button) and the speed controller in the drill are usually combined. Speed control is made by pressing the button with different effort. First, you should check the presence of voltage at the input and output terminals of the button. If there is no signal, you must carefully remove the button body and inspect all contacts. As a rule, burning or sticking of contacts is determined visually. All contacts must be thoroughly wiped with alcohol and sanded for sanding. After that, you should check again the presence of voltage. If there is no signal, the button should be replaced with a new one. The cause may be a breakdown of electrical contact with the wire. In this case, the wire should be soldered.
Connection diagram of the drill button with reverse.
The mechanism of reverse rotation is based on the system of closing and opening contacts. Its prevention is carried out similarly to the start button. In addition, you should check all the wires of the mechanism going to the brushes and the stator of the electric motor.
The reason for the inability to start the motor can be a failure of the starting capacitor. Usually the idle state of the capacitor is noticeable by the color change. But it is more reliable to measure its capacity and compare it with the nominal value.
Checking the electrical part begins with determining the integrity of the power cord (cable) using a tester or ohmmeter.
Measure the resistance between the contacts of the plug (the definition of the circuit wires) and the resistance of each core.Back to table of contents
Faulty gear or cartridge
Jamming of the cartridge or the presence of gnashing indicates the failure of the gearbox or bearings. First of all, you should disassemble the body of the drill and inspect the condition of the gears in the gearbox. Worn splines mounting or broken teeth gears indicate the failure of parts. This gear must be replaced. Gears inspect the entire circumference, smoothly turning the shafts by hand.
Bearings are checked by turning the shaft in them. When the shaft is tight, you should start by lubricating the bearings. If this does not help, then they are removed from the axis with a special puller. Hands scrolls bearing race. If movement is obstructed or other sounds are heard, the bearing should be replaced.
During long-term operation of the drill may be damaged chuck. Sometimes this is manifested in the impossibility of extracting the drill - the adjusting sleeve does not spin or, conversely, scrolls easily, and the sponges do not move apart. This indicates wear of the gear joint in the chuck under the influence of metal shavings and dust. In this case, the repair is reduced to the replacement of the cartridge. The fastening of the cartridge on the shaft is most often done by left-handed thread and fixed with a screw. You can remove the cartridge by unscrewing the screw, and turning the cartridge in the opposite direction with an effort. In some models of drills chuck installed with a tapered surface in the tension. In this case, it should be knocked out with gentle blows to the end from the side of the drill body.Back to table of contents
To repair the drill with your own hands you need the following tools and devices:
- set of wrenches and socket wrenches;
- bearing puller;
- emery sandpaper;
Often the drill breaks at the most inopportune moment. In order for this not to become a problem, you need to know how to repair the drill yourself. It is necessary to understand the design of the drill used and determine the cause of the malfunction.