General tips for choosing
This indicator, as it is defined in physics, expresses the intensity of rotation to which a certain body is subjected. The "body" here means the working part of the screwdriver. And already the speed of its twisting is directly related:
- with the strength of the material into which you can drive fasteners;
- the diameter of this fastener;
- its length.
But we must not forget that everything is good in moderation. For domestic purposes, the optimum torque is 10-30 Newton meters. Almost every task is successfully solved with the help of such equipment within an acceptable time frame. And if he does not dare, then he will need to call a professional. For the professionals themselves, there are screwdrivers with a torque of at least 100 Newton meters.
Such devices will easily insert a screw or self-tapping screw even into a very hard surface. But since both experienced builders and hobbyists alike are forced to work with a wide variety of materials, torque adjustment is a useful feature. Moreover, for different screws or self-tapping screws, it should not be the same.
The next important parameter is the speed at which the working nozzle rotates. At home, 500 rpm is enough. But if you need to use a machine for drilling, you need a pace of 1000 rpm. Since the screwdriver is often used in places where there is no electricity or it is unstable, many craftsmen prefer rechargeable models. Moreover, these devices allow you to "untie" from the sockets without using extension cords, which is very useful even in apartment buildings in a big city.
Batteries can be made on nickel-cadmium, lithium-ion and nickel-metal hydride element base. The vast majority of household screwdrivers are equipped with nickel-cadmium batteries. Due to the small number of duty cycles and the memory effect, they will have to be discharged and charged to 100%. Li-ion batteries do not have this disadvantage, but they are noticeably more expensive. The parameters of the current produced by the battery deserve a separate discussion.
No. 3. Drill types by purpose
Depending on what set of functions the drill has, the following main types of tools are distinguished:
- an ordinary drill, it is sometimes called a hammerless drill;
- hammer drill;
- drill screwdriver;
- drill mixer;
- angle drill.
Conventional drill
This is a drill without any bells and whistles. It does not have an impact function, so only wood, drywall, metal and other not very hard surfaces can be drilled with it. This tool is suitable for minor repairs in the country, in a barn, a wooden house. Conventional drills without impact function can be cordless or powered.
Impact drill
An impact drill is needed for those who are going drill holes in concrete, brick, stone and other hard materials. Such a tool costs less than the simplest puncher, but it has some limitations. Such a drill will not withstand constant work with dense materials - it will quickly break. In addition, frequent drilling in concrete and stone can negatively affect the accuracy of conventional drilling. If you have to work regularly with dense materials, then it is better to take a puncher.
The impact drill gets its ability to punch through hard materials thanks to its special design. During operation, not only rotational action is transmitted to the drill, but also impact.If in a hammer drill the blow is provided due to a complex electromechanical or electro-pneumatic unit, then in a drill the blow is achieved due to the presence of two ratchets. One is located inside the drill, the other is attached to the chuck. When the two elements are connected, the chuck and drill begin to move in the axial and translational direction, thus providing the function of chiselling, or impact. If necessary, the impact function can be turned off, the ratchets open and the drill works as usual. However, in some models the shutdown option is not provided - be careful when choosing.
A drill with an impact function is more expensive than a conventional drill, but cheaper than a hammer drill. Plus, it is also lighter than a hammer drill, so it can be called a versatile household tool.
When choosing a hammer drill, pay attention to the power of the tool. For the shock function to be normal, this figure must be at least 800 W
Also pay attention to the reverse rotation function and the presence of a safety clutch.
Drill driver
It makes sense to choose a drill-screwdriver when you also need a tool for tightening / unscrewing screws, self-tapping screws and screws. In the screwdriver mode, such a drill has a low rotational speed and high torque, in the drill mode, on the contrary. It is impossible to call the device completely universal, since such a drill is not suitable for drilling concrete and brick.
Drill mixer
A drill mixer differs from a conventional universal drill by the presence of special attachments in the kit, which allow you to conveniently mix liquid and semi-liquid compositions. The design of the tool, as a rule, provides for special handles for a comfortable grip during mixing. The drill mixer is suitable for mixing putties, adhesives, paints and other mortars up to 10 liters in volume and allows a more thorough mixing than with a manual process.
Angle drill
As the name suggests, such a tool is designed for drilling holes in the most inaccessible and narrow places, where you cannot get to with a conventional drill. The design of the device is characterized by the presence of a bevel gear and the location of the rotating shaft perpendicular to the body. Such drills, as a rule, have low power and there is no need to talk about any blow function.
An angle drill is a very specific tool, so it is better to take a regular model and, if necessary, use a special attachment - it is cheaper and in most cases wiser.
How to choose
Certain characteristics affect the duration and comfort of the work, as well as the effort that allows the tool to cope with the work of a given complexity.
Any screwdriver has a standard design with minor variations. Units and parts may differ in their quality and configuration.
Battery
The power source for the entire driving mechanism of the screwdriver. Gone are the days when cordless tools were exotic. Today, technologies make it possible to manufacture capacious batteries and chargers that fill the indicator from 20 minutes to an hour and a half. By changing the batteries, you can maintain the convenience of working without a power cord almost all the time.
There are several types of batteries for screwdrivers:
- Nickel-cadmium. Time-tested solution often found in low-cost options. They are still relevant where a great effort needs to be developed in a short time. In addition, this type will be the only way to work outdoors in winter, since it is better to protect all other types of batteries from the cold.
- Nickel metal hydride. Although they are more environmentally friendly than the previous ones, and the capacity is larger with the same dimensions, they have not become a full-fledged replacement for Ni-Cd, unlike finger batteries in the household sector.
- Li-ion.Reducing the cost of production and improving technology makes this type of battery the most demanded and widespread. Their properties allow them to be recharged at any time, and self-discharge has minimal values. In addition, in a small volume, it is possible to set a solid capacity. Therefore, if you see a 3 amp-hour battery, it will most likely be lithium-ion. True, this type of battery cannot be kept discharged for a long time, and they do not like the cold either.
Engine
Most screwdrivers are based on a DC reference motor, similar to the one you studied in school as an example. Its weak point is the brush assembly. The graphite brushes have to be changed periodically and create additional friction.
Today some expensive devices use brushless motors. They have a higher efficiency, and the current is supplied to the stator windings. Unfortunately, their price is still too high for mass distribution.
Impact mechanism
What a percussion mechanism installed on your cordless screwdriver?
Tangential Axial
Most users of electric screwdrivers do not think about how the impact mechanism works on their device.
- Axial impact in drills. It is the same as in conventional impact drills. The translational movement of the spindle with the chuck is carried out by two flat ratchets engaging with each other. In working mode, they rotate, and the teeth slip with a characteristic click, giving the spindle a forward-backward movement. Suitable for drilling holes in materials such as brick or lightweight concrete.
- Tangential impact. To present it more clearly, it is advised to remember the open-end wrench, which you put on the nut and knock on the free shoulder of the lever. This type of percussion instrument is also called impulse. At the base is a special part with two protrusions, which makes a full revolution around the spindle axis and, having accelerated, strikes with the protrusions on a special cross member. The mechanism is activated when the resistance to rotation reaches a certain value. At the same time, the twisting speed drops sharply, and the force increases many times.
Expert opinion
Torsunov Pavel Maksimovich
Axial impact is much more common as it is universal. The screwdriver with tangential impact does not have a chuck and is used in a rather narrow sphere - screwing in heavy fasteners, for example, wood grouse screws without preliminary drilling into the material.
What to look for when buying a cordless screwdriver
First of all, on the technical characteristics:
Battery capacity. The ability to work without recharging. Household appliances have a capacity of approximately 1.3 A / h (amperes per hour), professional 2 A / h and higher.
Voltage. Determines the size of the rotating element, in other words, the higher the voltage, the easier it is for the screwdriver to drill. For home use, a voltage of 8-14 volts is suitable. A professional screwdriver needs a higher indicator.
Charging speed. For domestic use, the charging speed may be slow. For a professional tool, this is an important indicator. Household appliances have a speed from 2 hours to 12 hours. For professionals from half an hour. Modern lithium batteries are charged in 30-40 minutes.
Engine torque indicates the force of rotation on a solid surface, measured in Newtons per meter.
Screwdriver motor rotation speed. For tightening / screwing in fasteners, an indicator of 500 rpm is enough
For drilling, at least 1000 revolutions are important.
It is also worth paying attention to the presence of a reverse (the ability to change the direction of rotation, how to screw it in with one click and unscrew the fasteners), the presence of a backlight, and additional functions of the punch.The weight of the tool is also important, especially for long-term work, the tolerance of high and low temperatures, the convenience of the case for storing the tool and the charger.
Criteria for choosing screwdrivers
- The purpose of the screwdriver and the frequency of use
First of all, you need to determine what this tool is needed for. If frequent use is not planned, then you should not choose a model with high technical characteristics and advanced functionality. You need to limit yourself to a common tool for household use. An important factor is access to the mains power source - this will save time for additional recharging of the batteries.
- Battery type and capacity (for cordless screwdrivers)
There are several types of rechargeable batteries used to power screwdrivers:
- nickel metal hydride (Ni-Mh);
- nickel-cadmium (Ni-Cd);
- lithium-ion (Li-Ion).
The most popular models in the opinion of buyers are screwdrivers with lithium-ion rechargeable batteries. They are small, have no memory effect and charge quickly. Nickel-cadmium batteries have a higher weight and a long recharge time, while they are completely insensitive to environmental conditions and work perfectly at subzero temperatures. Nickel-metal hydride batteries are very bulky and heavy, but have low self-discharge and no memory effect.
- Battery capacity and charging time
How long does the battery hold? Another important factor when buying a new screwdriver. In the case of long-term continuous use, it is necessary to choose batteries with a capacity of 2 Ah or more. It is worth noting that the best manufacturers provide an additional battery in the package, which can be used while recharging another. Also, batteries with a larger capacity than those provided for in the kit may be suitable for the tool (be sure to read the instructions). In terms of charging time, the type of charger plays an important role. Pulse chargers have the highest rate of accumulation of battery charge.
- Maximum torque and speed
These parameters characterize the functionality of the screwdriver. Torque is the ability to tighten the fastener (a tool with a higher torque handles larger fasteners and stronger material), and rotational speed is capable of drilling holes (determines the maximum diameter and material availability).
- Comfort and convenience
It is worth paying attention to the weight of the tool, the convenience of the handle (most often they are made in a rubberized version), switches and buttons. The screwdriver should comfortably "lie" in the hand, all operations to change modes, change equipment, it is advisable to perform without changing position and with one hand
- Chuck type
There are the following types of screwdriver chucks:
- key;
- quick-clamping;
- hex.
Key cartridges have the most reliable fastening of the tooling, although its change takes quite a long time and the presence of a special device. Keyless chucks are characterized by quick replacement of drills or bits, while they are not always durable and have slight backlash over time. In hex chucks, the attachment is fastened to the seat directly in the screwdriver spindle.
- Special functionality
Among the most common additional functions of screwdrivers offered by manufacturing companies, the following should be highlighted:
- electronic speed control;
- the possibility of reversing to remove the drill or loosen / unscrew the fasteners;
- pulse mode (periodically increased torque) for working with firmly stuck screws and self-tapping screws;
- the presence of spot illumination of the place of work;
- fixation of the spindle for easy change of attachments and drills in the chuck, etc.
- Screwdriver complete set
A very good gift for buying a new tool will be the presence in the set of a special case for storage, additional batteries, a set of bits and other useful little things.