How To Assemble A Screwdriver Gearbox

Breakdown reasons

Like any mechanical unit, during the operation of the gearbox, the friction force affects the parts, from which they gradually wear out or wear out and lose their “coupling”. In order to avoid this, all parts of the unit must be properly lubricated.

Therefore, the first reason for the breakdown of the gear unit. Lack of lubrication (but there may be too much).

The gearbox is also affected by such a “scourge” of mechanics as dust. It settles on the parts and heats up with them during operation. This is especially dangerous for plastic gears, since they are deformed under the influence of heat from dust. Which leads to breakdown.

Finally, one more nuisance for the reducer. The ingress of foreign particles into it. Blocking between the teeth, they jam them. Because of this, when the motor shaft rotates, an excessive load is created on other structural elements, which leads to their destruction.

Home workshop: how to repair a screwdriver gearbox?

Any tool, regardless of model and brand, sooner or later breaks down. Screwdriver. Not an exception: individual parts and assemblies wear out over time, and without proper care or under force majeure, they may refuse.

The main functional load during tool operation is distributed through the gearbox between the motor and the chuck, so if something happens to the gearbox. The work will become. In order not to spend money on repair services, it is enough to use the advice of the masters to restore the operation of the unit yourself.

  • Device and principle of operation
  • Kinds
  • Breakdown reasons
  • DIY repair
  • How and how to lubricate?

DIY repair

In a home workshop, it is not so difficult to repair a gearbox. Repair is reduced to disassembling the unit into separate parts, checking the integrity of their structure, purging and lubricating, followed by reassembly. The process is subdivided into the following stages:

  • Separating the gearbox from the engine and removing (usually with a chuck) from the screwdriver casing.
  • Unscrewing the housing and removing the locking washer.
  • Sequential removal of satellites and transfer plates (2 or 3, depending on the design).
  • Removing the ring gear and checking the ball bearings (they can roll around the seal, but should not roll outside of it).

After removing all parts, they must be cleaned of “old grease”, wiped dry and make sure that they are NOT damaged.

Then the craftsmen recommend to fold them in the reverse order “dry” and make sure that the chuck spindle also rotates when the satellites rotate. If the rotation is carried out without scrolling, then it can be assembled back.

First, bearings are placed in the recesses in the housing, on which the annular gear is installed. Then, one at a time, put the Transfer Plates, with the satellites installed on them and put on top of the fixing washer.

Device and principle of operation

The gearbox is a complex mechanical transmission unit, through which the motor-power unit transmits torque to the chuck.

Two or three gear stages are installed in the gearbox.

The construction of the unit of the “household” two-mode screwdriver includes:

  • Plastic case. A small drum, which is attached to the cartridge. The body itself is fixed motionless, and the chuck shaft is inserted into a clamp on one of the transfer plates
  • 2 or 3 Transfer Plates (Carrier). A round metal plate, on one side of each there are 3 protrusions for small gears. On the other hand, one of them is a clamp for the chuck shaft, and on the other (or 2 others) there is another so-called N. “Planetary” gear, which rotates three small gear wheels;
  • 6 or 9 small cogwheels (three each: they can be of the same or different thickness). These are the so-called “satellite” gears, which are installed and rotate freely on the projection of the transfer plates. With their teeth, they interact with the sun gear located between them and with the ring gear, which is located on the inner surface of the housing;
  • Ring gear. A metal ring with teeth on the inside and small ones protruding on one of the rings on the outside. On these protrusions and ball bearings, it fits on the inner surface of the housing.

The parts are lubricated, assembled in series and installed inside the ring gear, which lies inside the housing drum (it has a seal with a groove for ball bearings and gear projections). After that, the surface of the open satellites is closed with a metal washer, in the center of which there is a hole into which the engine shaft enters with another gear fixed to it.

During the operation of the screwdriver, the gear wheel on the engine shaft rotates the upper satellites, and they, rotating around their axis and, along the ring gear, respectively, transmit the movement to the next carrier. Depends on the number of plates and small gears. The rotation speed will decrease proportionally.

As can be seen from the device of the gear unit. They are subdivided, depending on the number of transfer plates, into:

  • Two-stage.
  • Three-stage. In this case, another plate with a “Planetary” gear and 3 satellites is added to the design.

Another indicator by which gearboxes are divided. This is the material from which its parts are made.

In the production of satellite gears the following are used:

  • Plastic. Such structures are lighter, but their reliability is lower than in the metal counterpart;
  • Metal. They are durable and with proper care and lubrication will work like a clock.

How and how to lubricate?

During assembly, each part is lubricated with a synthetic (semi-synthetic) or mineral lubricating paste (grease). These substances differ in viscosity and durability. The smaller it is, the more often the details have to be recoated. After the gear unit is disassembled, it is recommended to coat each element with grease separately, gradually putting the unit together. Apply the lubricant with a brush and spread over the entire surface of each part.

Another way. Use specialized gear oil. Oils have a liquid consistency. They are used in the same way as grease, or sometimes they are poured into the gearbox, and not disassemble it, if a special hole is provided for this in the screwdriver design.

Thus, having understood the device of the gear unit of the electric screwdriver, removing it from the tool, checking all the parts and, if necessary, changing the lubricant on them will NOT be difficult even for a novice master. If he performs this operation regularly 1-2 times a year. The risk of screwdriver breakage will be minimal.

How does a two-stage screwdriver gearbox work

The principle of the whole system is that:

  • The sun gear of the motor allows the satellite to rotate. The rotation itself is performed along a trajectory in the form of a circle of an annular gear. Therefore, it is clear that the carrier spins at a slower pace than the motor itself.
  • Then the first carrier transmits the torque to the second three satellites. The transmission process takes place through the sun gear. At the same time, the second trinity also rotates along a trajectory in the form of a circle, and in total the second carrier takes on much less revolutions. It integrates with the base shaft of the chuck.
Read more:  What is the difference between a screwdriver and an electric screwdriver

The entire system is equipped with a critical load mechanism, which also has a finite number of holes. They are made in order to subsequently insert spring-loaded fingers with ends hardened by means of high frequency current. Such a system has a case hardened edge related to the gearbox.

The sleeve is also equipped with a notch, which was created by the tip of the fingers of the first disc. The finger circuit can be adjusted by simply twisting or unscrewing the nut threads, due to the fact that this mechanism has constantly reinforced or compressed springs. Excessive pressure is due to pulling through the ratchet fingers, due to which the work of rotating the chuck in the gearbox ends.

This is the structure of a two-stage gearbox.

All gearboxes of various screwdrivers are arranged according to the same principle, but they differ only in the number of satellites, for example, a three-stage gearbox simply acquired an additional mechanism.

It is also worth noting that the screwdriver gearbox device includes unusual cylindrical, bevel and worm gears. In order for them NOT to fall out, when assembling the tool, they are inserted at a certain angle, and such measures do not allow them to fall out when the entire device is tilted.

The gear ratio of the gearbox never changes. Adjustment of the number of rotations of the cartridge and the frequency of blows is carried out using a special electronic regulator. In addition, there are models of tools with gearboxes with two speed modes. The gearbox can be removed from the ratchet with housing. The fixation of the cartridge is created by means of a screw, which in turn is unscrewed thanks to the provided cartridge right thread.

During the rotation of the chuck under load, there is always a need for more force, for example, when the final stage of tightening the screw comes. Then the load level regulator starts to work. The force of the regulator springs is insufficient to hold the ring gear and it flies off the balls. It turns out that clicks begin to be heard when the chuck stops rotating.

The whole process of working with the device should NOT last more than 15 minutes, since every quarter of an hour should be accompanied by the cooling of the device, because the continuous operation of the device reduces the operating period of the device.

Gearbox operating principle

Figure 1. Typical device of the screwdriver gearbox.

The perforator is a convenient and easy-to-use device, the beginning of its use is associated with space flights, where it was used by astronauts. New models of screwdrivers are being produced, so the demand for them does not fall. This device is suitable for various household items, as well as repair.

The action of a screwdriver gearbox resembles the operation of a drill gearbox, the distinguishing characteristic is the complete set of the part and the gear ratio. The gearbox of any of these tools requires regular inspection. The uninterrupted operation of these devices is associated with periodic checking of the working condition of the gears and the lubrication of the gearboxes, which sometimes requires replacement.

The gearbox mechanism includes spur, bevel and worm gears. The gear ratio of the gearbox is constant. The number of revolutions of the cartridge and the frequency of blows are regulated by means of an electronic regulator. There are models of devices with two-speed gearboxes. During operation, the device must not be overloaded, that is, it must not be operated for more than 15 minutes. The perforator must cool down every quarter of an hour, since the device cannot work continuously.

Diagram of the internal structure of the screwdriver.

There are two-stage and three-stage gearboxes for screwdrivers, which is determined by the number of elements in the mechanism. The carrier and the satellites are interconnected with the gearbox shaft, on which the cartridge of the device is attached. These parts are included in the ring gear, which must be firmly fixed in the gearbox housing.

To fix this gear, projections are used, abutting against special protruding balls, to which the ring is attached. Due to the ring, the balls are springy, which is also influenced by the presence of a spring related to the load limiting system. The position of the mechanism regulator depends on the degree of spring tension.

Depending on the material used to make the satellites, gearboxes are divided into metal and plastic. It all depends on which tool is used: professional or amateur. If the modification of the hammer drill is a household one, then the provision of a torque reaching up to 10-15 Newton meters (Nm) is due to plastic gears.

Cordless screwdriver device.

In addition to the ring gear, the gearbox includes a sun gear and a central gear, which is pressed onto the armature shaft; a ring gear cylinder having an inner circumference along which the satellites can move through the teeth on the circumference. The satellites also have teeth. Rotating around their own axes and the axis of the central wheel, they can constantly engage while working with the tool. Satellites are planted on each of the pins related to the carrier.

The optimum speed due to the metal satellites is ensured when the gearbox is operating at maximum torque, which fluctuates in the range from 25 to 150 Nm. Depending on the torque, screws of one length or another are used, suitable for different materials, i.e. wood, steel or concrete. The presence of a regulator in the device allows you to select the most suitable torque for the purpose of performing work with a hammer drill.

Features of household screwdrivers.

Often, the gearbox is a fairly powerful steel element, but plastic models are cheaper. The motor shaft of the device is upset by a gear, and the reducer has gears in the amount of three pieces. This drive is called planetary. The gearbox itself is quite simple to remove from the case, you can assemble it without much difficulty.

To prevent gears from falling out of the gearbox, insert them at an angle. This prevents the gears from lunging when tilted. The gearbox is removed from the ratchet with the housing. The chuck is fixed by the screw, and the chuck thread is provided for unscrewing it, which is right.

The impact mechanism of the hammer drill is based on the transmission of the rotary motion emanating from the engine to the chuck. A professional worker will be able to carry out high-quality repairs, who will NOT harm the device and his own health, which will be safe thanks to his work experience.

Screwdriver specification table.

To properly disassemble a screwdriver of any model, you will need detailed knowledge of their design. The main parts of a planetary gear unit are:

  • Gears.
  • Drove.
  • Satellites.

These parts and assemblies can be made of plastic or metal. In the process of disassembling the gearbox, the cartridge is snapped off from it due to the spring, which controls the compression ratio. A cone is installed along the chuck, which is rotary. The spring coming from the chuck produces pressure on the balls in the body. Here the pressure of the balls goes to the reducer. When disassembling, they spill out, so disassembly should be carried out on a cleaned surface so that not a single part is lost.

The ring gear has rotating satellites internally that drive the sun gear of the engine. The rock drill carrier has a lower speed than its motor. The first carrier transmits the torque to the second by rotating the sun gear. This makes it possible to reduce the speed of the second carrier connected to the chuck shaft. The operation of the three-stage gearbox is similar, but with the addition of an additional planetary gear set.

Read more:  How to Assemble a Trimmer Starter Spring

Electrical components of the screwdriver.

In any case, the sequence for disassembling the screwdriver gearbox includes the following steps:

  • Removing the cartridge.
  • Unscrewing the case.
  • Disconnecting the gearbox from the engine.
  • Removing the plate.
  • Removing all parts from the body.
  • Unscrewing all the bolts that connect both halves of the gearbox.
  • Correction of the spring diameter with the introduction of pliers to the smaller side in order to improve the gear engagement.
  • Dismantling the coupling by removing the retaining ring, washers, bulk bearing.
  • Removing the shaft.

The gear unit consists of three gears that receive rotation from the central gear of the motor shaft, as shown in Fig. 1. The outer sleeve is set in rotation due to the existing rifled teeth meshed with a gear, which belong to the first and second stages of reduction.

The perforator device is equipped with a critical load mechanism, which has a disc with a number of holes. They are drilled so that spring-loaded fingers can be inserted with high-frequency current hardened ends. This design has a hardened liner edge that belongs to the gearbox.

The sleeve has recesses made specifically for the fingers of the first disc. The finger mechanism is adjusted by the usual tightening and unscrewing of the nut thread, which is associated with the strengthening or compression of the springs of this mechanism. Excessive force is associated with pulling through the ratchet fingers, so the process of rotation of the chuck in the gear mechanism stops.

When buying a screwdriver, keep in mind that manufacturers of this type of tool DO NOT manufacture repair kits for the device.

Almost all repair of the gearbox after disassembling the tool will be reduced to its cleaning and lubrication.

A common cause of screwdriver breakage. Debris falling into the plain bearing.

If parts are found that are worn out, then the entire assembly should be replaced. The high-quality work of screwdrivers is not associated with the presence of excessive grease in the gearbox.

A screwdriver after long-term use can have not only electrical faults, but also mechanical ones. These types of breakdowns can be associated with the appearance of abnormal sounds, indicating that the bushing or bearing is worn out. Therefore, after the inspection, damaged parts are identified, which are then changed to new elements.

If, during the operation of the screwdriver, sticking occurs, which will be accompanied by a grinding sound, then this malfunction can be attributed to the poor-quality operation of the gearbox.

The main causes of mechanical damage:

  • Damage to the bearing or reducer sleeve.
  • Worn gear teeth or clutches.
  • Deformation of the gearbox shaft.
  • Damage to the pin with which the satellite was fixed.
  • Chuck beating.

If chuck beating is detected, a bent gear shaft may be detected. At the same time, this may be due to the high wear of the bearings. Various models of screwdrivers include not only bearings, but also copper bushings as part of their device.

The operation of the gearbox clutches is associated with constant wear of the clutches with teeth. The operation of the tool as a whole, associated with certain modes, may be accompanied by a weakening of the actions associated with the high-quality operation of the couplings, their slippage. These elements, similar to washers, will be worn out.

Recovering these items is NOT possible, since they cannot be recovered once their condition has been determined. Therefore, you should purchase new parts for the gearbox and replace the old ones.

The principle of operation of a two-stage screwdriver gearbox

  • The sun gear of the motor rotates the satellites. Rotation occurs along a circular path of the ring gear. From here it becomes clear that the carrier rotates slower than the motor itself.
  • Further, the first carrier gives the torque to the second trinity of satellites. The transmission takes place via a sun gear. The second trinity also rotates in a circular path as a result. The second carrier gets even less revs. It connects to the main shaft of the chuck.

This is a two-stage gearbox diagram. The device of the screwdriver gearbox is the same, only the number of satellites differs. For example, for a 3-stage gearbox, another mechanism is added.

Features of the device and repair of the screwdriver gearbox

  • 20-12-2014
  • 28
  • 446
  • Gearbox operating principle
  • What is a reducer?
  • Types of gearboxes for screwdrivers
  • Features of the assembly of gearboxes
  • How to properly disassemble the gearbox?
  • Causes of screwdriver breakdowns
  • The device of screwdrivers is familiar to many professional builders, who can disassemble it and correctly repair it. In any case, this can be done only by understanding all the details of the screwdriver mechanism, including the gearbox. This element should be responsible for the process of transferring rotation from the engine to the chuck device, which activates the impact mechanism of the tool.

    How To Assemble A Screwdriver Gearbox

    Network screwdriver device.

    The design of the rotary hammer on the gearbox has its own characteristics. The location of the gearbox can be horizontal or vertical. The heavy weight and large dimensions of rock drills with a vertical gearbox position make them more powerful and reliable, with a high impact force. These types of tools are used mainly by professional builders, and not by craftsmen working at home. In general, the gearbox determines in which mode the tool operates. The work of the punch is reduced to two or three functions.

    How to disassemble a screwdriver gearbox

    The process of disassembling the gearbox includes the following procedure:

    • First you need to remove the cartridge. For this, it is better to use a 10 mm hex wrench.
    • Then you should clamp the small end of the key in the chuck and make a short start of the tool. This will allow the key to hit the table at the highest speed of the electric motor.
    • If the gearbox does not turn on at all, you need to clamp the spindle in a vice. This position will make it possible to calmly disassemble the gearbox into parts.

    After carrying out these manipulations, you can begin to perform the necessary operations, that is, lubricate the parts or replace them. The main thing is that there are new parts.

    By the way, it is better not to use gears or couplings designed for the second models of the screwdriver, although they may look completely identical. Also, do not often turn on the tool at the highest power, as this usually leads to breakdown of the entire mechanism or its SEPARATE parts.

    Finding a malfunction and repairing a screwdriver gearbox

    People could successfully carry out the procedure for fastening various elements with nails in the distant past, but they began to use nails with a spiral groove quite recently. The spiral of the self-tapping screw helps it to better cut into the material, and the notches on the head make it possible to connect the tool and the self-tapping screw to each other to create more pressure when screwing.

    Self-tapping screws differ due to the different types of head profiles, but the most popular are the ones with special cutouts for the cross and slot.

    It is clear that without the help of a screwdriver, it is almost impossible to screw such self-tapping screws. With it, the process will be easier, if you do not take into account the fact that there can be more than a hundred self-tapping screws.

    In order to simplify the entire tightening procedure, a drill with a gearbox for manual use was invented. A part of the screwdriver was fixed into the cartridge, and it remained only to tighten the handle so that the cartridge made rotational movements. The disadvantage of this method was the periodic tearing off of the self-tapping notch, and the speed was extremely difficult to control, which led to a constant breakdown of the self-tapping edges. In Soviet times, due to such situations, all self-tapping screws were added to the material using hammers.

    Read more:  Alteration Of A 12v Screwdriver For Lithium Batteries 18650

    A few decades later, they finally came up with a screwdriver, and everything went much easier, because the edges did not break off, and mounting became possible even without the presence of sockets, since the screwdriver device implied the presence of a battery. The screwdriver itself was created for twisting and unscrewing screws, nuts and screws, but some models can drill and chisel. This thing is very convenient in everyday life, but at times it breaks down, and then urgent high-quality repairs are required.

    Some screwdriver models are equipped with an automatic self-tapping screw feeder


    In most cases, charger problems arise for the following common reasons:

    • If the fuse is blown;
    • The primary winding of the transformer has broken;

    It does not matter under what brand the screwdriver that you own is released. If, when you turn it on, it simply does not start, then the first thing you need to do is make sure that its battery is charged. To find out, you need to put the battery on charge for a couple of hours. After the specified time, remove the battery and reinsert it into the device. Make sure the battery is working properly. If the screwdriver does not work, then you will need to carry out a number of manipulations using a device such as a multimeter (you can use a special tester instead). Using this tool, you can diagnose the existing parts of the screwdriver.

    With the help of these devices, it will be necessary to determine what exactly is the problem of equipment refusal to launch. In this case, either the battery or the charger is to blame. To find out what the cause of the malfunction is, you will need to carry out the following procedures:

    • First, fix the multimeter in the DC voltage measurement mode (set the rating to 20 V);
    • If the battery in the screwdriver has a rating of 24 V, then the device will need to be set to 200 V;
    • Plug the charger into a power outlet;
    • And now the output voltage at the terminals of the charging unit has died.

    The readings of this device should be approximately 2 V more than the rating of the battery being diagnosed. If this indicator is much lower, or there are values ​​at all, then this means that the problem lies in the malfunction of the charger itself, and not the battery in the device. It will be possible to repair this part only if you can boast of certain knowledge and skills in electronics. If there are any, and you cannot fix the charging unit, then you will need to purchase a new part of the same brand.

    Features of screwdriver repair

    • Device and principle of operation
    • Frequent malfunctions
    • How to disassemble?
    • How to repair it yourself?
    • Charger
    • Battery
    • Button problems
    • Reducer
    • Replacing brushes
    • Engine
    • Ratchet
    • Recommendations
    • Screwdriver. It is a popular and irreplaceable tool. It is used both in domestic conditions and at various construction sites. In the process of many works, you simply cannot do without it. But as befits a complex and functional technique, the screwdriver is prone to breakage. Even the most expensive and high-quality instrument is not insured for this. Today we will take a closer look at how you can fix such a useful device, and also find out what problems happen with screwdrivers most often.


      In modern screwdrivers, there is a DC motor in a cylindrical housing with magnetic elements. To check the condition of the engine, it is necessary to disconnect the gearbox, as well as the wires going to the start button. Measure the resistance of the armature winding (part inside) using a multimeter. If you did NOT see any shown on the device, then this will indicate that there is a break. Too small values ​​will confirm that a short circuit has occurred in the device.

      The collector resistance parameter must be measured on the shaft and on each of the plates. It should be zero. Breakdowns in the anchors can cause the device to turn off during its operation. Power will be lost, sparks and smoke may appear. When the engine breaks down, the gears often remain NOT damaged. Because in the fate of the Lion engines it is pressed on the shaft, it can be difficult to remove it. Having acquired a specialized removable element or resorted to using improvised means. DO NOT do this with a nailer or pliers. Spoil the gears. You should act differently.

      • Stock up on a piece of profile or channel. Make neat longitudinally spaced notches using an angle grinder.
      • Install the shaft in the groove in a direction perpendicular to the profile. Pry the gears.
      • Lay the prepared profile on 2 rigid bases so that the engine hangs between them.
      • Take the nail and hammer. Tap the edges of the shaft gently. After that, the gear will slide smoothly.
      • Now you can put the gears on the new engine using a hammer and a base with a hard surface.

      How to disassemble?

      Often it will be possible to identify this or that malfunction of the screwdriver, as well as to repair it only after correct disassembly. Since almost all such tools are similar to each other and have the shape of a kind of angle pistol, useful recommendations should be followed when disassembling them.

      • The first step is to disconnect the battery pack from the device battery. To this end, it will be necessary to gently press the latch and at least carefully unfasten the module.
      • Along the perimeter of the tool, you will need to Unscrew the screws using a small Phillips screwdriver.
      • By unscrewing all the fasteners, the two parts of the body base can be easily disconnected from each other. But at the same time it is extremely important to hold the rest of the elements of the existing structure, which are fixed in the grooves.
      • Very carefully it is necessary to remove the part responsible for gear shifting. Together with it, carefully remove the start button and the reverse mechanism.
      • After that, you can further carefully disassemble the technique. From the removed half of the housing Remove the gearbox. To remove it from its place, you will need to return the gearbox at the landing site.


      If a ratchet breaks in such a tool, then it will need to be detached from the gearbox in order to detect the causes of the breakdown. Often, special rods are fixed in the coupling, set aside for adjusting the forces. There are also devices where instead of rods, a pair of balls are installed in each hole. They are pressed with a spring.

      Replacing brushes

      Graphite brushes are located at the end of the engine at the junction with the button. They can be located in the inside of the case, or outside. If at least one brush is worn out, then both will have to be changed. To do this, you will need to disassemble the engine, carefully bend the flare with pliers. Then the part is removed from the brush. Old elements are extracted from it and new ones are installed. After that, you need to assemble the base back.