Power drill is the most widely used and common electric tool in life.
The principle of electric drill is well understood. A motor outputs rotating torque and drives the drill to rotate through the gearbox or other speed change mechanisms.
The impact driver is generally used with a drill bit with hexagonal tail. In woodworking, it is mainly used to screw screws into wood, and it can also be used to tighten or loosen metal bolts and nuts.
On the basis of the electric drill, the impact driver adds an impact rotating mechanism. After changing the speed, the torque output by the motor does not directly drive the drill bit, but drives a large iron bucket with a notch to rotate. The big iron barrel is sleeved outside the shaft behind the drill bit. The shaft behind the drill bit also has a projecting part, which is a bit like a mortise tenon structure and fits with the notch of the iron barrel. Behind the big iron bucket is a spring. With the rotation of the iron barrel, the spring gradually pushes the iron barrel downward, and then the protrusion at the lower end of the iron barrel will hit the protrusion of the rotary shaft of the rotary head. This sudden impact will instantly transmit torque to the rotary shaft of the drill bit, thus driving the drill bit to rotate once and again. Because of this mechanism, the drill bit will not move until the iron bucket and the shaft bump contact, and only the iron bucket is rotating. Therefore, the drill bit of impact driver rotates not continuously, but one by one.
Because of this principle, the machine shell of the impact driver will not move, and the impact rotating mechanism will all occur inside the machine. The drill itself has no axial back and forth movement, but has intermittent sudden rotation on the rotation movement around the axis. This is also the source of the “dahdahdahdahdah” sound when using the impact driver.
The principle of percussion drill is that there is a pair of metal discs engaged with each other on the rotary shaft behind the drill bit. In fact, it is cam, which can turn the rotation of the rotating shaft into axial linear reciprocating motion.
In this pair of metal discs, the upper metal disc is integrated with the shaft. With the shaft rotating, the lower metal disc is separated from the shaft and is permanently fixed. Because there is an angle between the occluding contact surface of the pair of metal discs, there is a gap between them. The upper metal disc will move upward along the contact surface. Once it moves out of the serrated contact surface, the spring will immediately press it back. Then continue to move upward, and move out of the contact surface of the next saw tooth, which is pressed back by the spring. If the saw tooth contact surface of this pair of metal discs has twenty saw teeth, then every revolution of the shaft will produce twenty reciprocating actions in the axis direction.
Because of this working principle, only the part of the drill bit below the metal disk is tightly pressed against the working face. The part of the whole machine above the metal plate actually moves up and down. The reciprocating distance is the height of the saw tooth. Each reciprocating is hitting the drill bit with the weight of the whole machine. Therefore, when using the impact drill, you will feel strong reciprocating impact and vibration.
The principle of the electric hammer is that the drill bit part and the driving part are separated, and there is a gap between them. There is a cylinder piston on both sides of the gap. Through the cam crankshaft and other mechanisms, the rotating torque of the motor is transformed into the reciprocating motion of the right piston, and the right piston continuously impacts the left piston in the linear reciprocating motion, thus playing the role of hitting the drill bit. Through other additional mechanisms, the drill can rotate, so that the drill can rotate while striking. To put it simply, every time the right piston reciprocates, it will hit the left piston once, thus hitting the drill once. So the name of the machine is “electric hammer”. Because the piston driven by the motor directly hits the drill bit, the vibration will be much smaller than that of the percussion drill.
Post time: Oct-05-2022