Brief history
The birth of the world's electric tools began with electric drills - in 1895, Germany developed the world's first DC electric drill. This electric drill weighs 14 kg, and the shell is made of cast iron. It can only drill 4 mm holes on steel plates. . Then there was a three-phase power frequency (50Hz) electric drill, but the motor speed failed to break through 3000r/min.
In 1914, an electric drill driven by a single-phase series motor appeared, and the motor speed reached more than 10,000r/min.
In 1927, an intermediate frequency electric drill with a power supply frequency of 150-200 Hz appeared. It not only has the advantages of high speed of single-phase series motor, but also has the advantages of simple and reliable structure of three-phase power frequency motor. However, due to the need for intermediate frequency current power supply, Use is restricted.
In the 1960s, a battery-operated electric drill without a power cord that used nickel-cadmium batteries as a power source appeared. By the mid-to-late 1970s, due to the reduction in battery prices and shortened charging time, this type of electric drill was widely used in Europe, America, and Japan.
The electric drill used cast iron as the shell at first, and later changed to aluminum alloy as the shell. In the 1960s, thermoplastic engineering plastics were applied to electric drills and realized double insulation of electric drills.
In the 1960s, electronic speed control electric drills also appeared. This kind of electric drill uses components such as thyristors to form electronic circuits, and the speed is adjusted according to the depth of the switch button being pushed in, so that the electric drill can be used according to the different objects to be processed (such as different materials, drilling diameters, etc.). Choose a different speed.
Principle Edit
The working principle of the electric drill is that the motor rotor of the electromagnetic rotary or electromagnetic reciprocating small-capacity motor performs magnetic field cutting and works, drives the working device through the transmission mechanism, and drives the gear to increase the power of the drill bit, so that the drill bit scrapes the surface of the object and penetrates the object better. .
Classification
Electric drills can be divided into 3 categories: hand drills, impact drills, and hammer drills.
1. Electric hand drill: The power is the smallest, and the scope of use is limited to drilling wood and being used as an electric screwdriver. Some electric hand drills can be changed into special tools according to the purpose, and there are many uses and models.
2. Impact drill: The impact mechanism of the impact drill has two types: the dog tooth type and the ball type. The ball impact electric drill consists of a moving plate, a fixed plate, and steel balls. The moving plate is connected to the main shaft through threads and has 12 steel balls; the fixed plate is fixed on the casing by pins and has 4 steel balls. Under the action of thrust, the 12 steel balls roll along the 4 steel balls. Make the cemented carbide drill bit produce rotary impact motion, which can drill holes in brittle materials such as bricks, blocks, and concrete. Take off the pin, so that the fixed plate rotates with the movable plate without impact, and can be used as an ordinary electric drill.
3. Hammer drill (electric hammer): it can drill holes in a variety of hard materials, and has the widest range of applications.
The prices of these three types of electric drills are arranged from low to high, and the functions are also increased. The selection needs to be combined with their respective scope of application and requirements.
The difference between hand drills, impact drills, hammer drills and electric picks
The electric hand drill only relies on the motor to drive the transmission gear to increase the power of the drill bit to make the drill bit scrape through metal, wood and other materials.
When the impact drill is working, there is an adjustment knob at the drill chuck, and there are two modes of adjustable drill and impact drill. However, the impact drill uses the gears on the inner shaft to beat each other to achieve the impact effect, and the impact force is far less than that of the electric hammer. It can also drill reinforced concrete, but not as well.
The hammer drill (electric hammer) is different. It uses the bottom motor to drive two sets of gear structures. One set realizes drilling, while the other drives the piston, just like the hydraulic stroke of an engine, which produces a strong impact force, accompanied by the drill. Effect. Power can split a stone into gold.
The electric pick is to let the motor drive the swinging mound to run in the form of bouncing, so that the pick has the effect of chiseling the ground. The hydraulic pump pick uses the gas pressure transmitted by the air compressor to drive the pump hammer in the electric pick to bounce back and forth, thereby producing the effect of the pick hitting the ground, but the electric pick only chisels, and its pick does not rotate.
All in all, electric drills can only drill, and impact drills can drill and have a slight hammering effect. Hammer drills can drill and hit higher hammers, while electric picks only do hammering and can't drill.