What Is a Nut Runner?
A nut runner is a power tool that can automatically tighten nuts.
Some models can be used for screws and bolts by changing sockets as well as nuts. Most nut runner is hand-held, but there are also fully automated models. Nut runners can set the tightening strength, thus ensuring homogeneous and highly precise tightening.
Nut runner is widely used in fastening areas where reliability is required because they enable highly accurate and reliable fastening as well as simplify the work.
Uses of the Nut Runners
Because of the homogeneity and high precision of tightening with nut runners, they are widely used in automobile parts, motorcycles, shipbuilding, and other areas where safety assurance is required. They are also often used for equipment inspections requiring more precise tightening, such as at gas stations and chemical plants, and at construction sites where steel frames of buildings and other structures are assembled.
Nut runners may also be incorporated into fully automated automatic assembly equipment. When selecting nut runners, the torque range of the nuts and bolts to be used should be checked.
Principle of Nut Runners
Nut runners can be broadly classified into two types: those driven by an electric motor and those driven by air pressure. The motor is used to rotate the torque, and the nut runners are set to automatically stop when tightening is completed.
1. Drive by Electric Motors
Since the torque and angle are electrically controlled by an electric motor, it is more accurate than a pneumatic drive, and work history and data can be kept. Cordless types are also available and have become popular in recent years.
It is important to choose an insulated or pneumatically operated nut runner if there is a risk of electric shock due to its tendency to generate heat. Also, since retightening is not possible, it is necessary to loosen the nut once when retightening it again.
2. Pneumatic Drive
An air compressor is required, and compressed air is used to turn an air motor to control torque. The advantage is that there is no risk of electric shock, but the disadvantage is the high cost of electricity due to the use of an air compressor. This type has been used for a long time because it generates less heat than an electric motor drive and is suitable for use over a long period.
Nut Runners Structure
The electric type uses an AC servo, DC brushless, or other motor that can control the number of rotations, while the air-driven type uses an air motor driven by pneumatic pressure. The control unit is either built-in or installed separately. Their rotation is transmitted to the drive shaft via a planetary gear reducer.
Some high-performance types have a torque detection function and can control rotation by torque, while others can be equipped with an arm that detects position and posture.
Other Information on Nut Runners
1. Nut Runners and Electric Drivers
Nut runners are nut-tightening tools, hence the name, but they can also be used for screws and bolts that are fastened by rotation. The difference between electric screwdrivers and impact wrenches is that the tightening torque can be accurately controlled.
While electric screwdrivers and impact wrenches have a structure in which the shaft idles when the specified torque is reached, electric nut runners have a function in which the rotation of the motor decelerates as it approaches the specified torque value, thereby stopping the motor at the exact torque value. In recent years, electric nut runners have become the mainstream for more accurate tightening.
The nut runners perform tightening while controlling the rotation speed and torque according to the torque value at the time of tightening. Although their rotational speed is inferior to that of electric screwdrivers and impact wrenches, they feature less error in torque value after tightening and less noise during operation.
2. Torque Control of Nut Runners
Recent nut runners monitor changes in torque and angle during tightening to determine whether tightening is good or bad, and can detect such problems as bolts being inserted at an angle, washers being forgotten, or two washers being inserted at the same time. Such data can be stored in the nut runners themselves or wirelessly transferred to a PC or other device and recorded as data during assembly.
In addition, advanced models can also detect the posture and position of the nut runners. It can determine the position of the hole to be tightened to determine if the screw or bolt being tightened matches the specified one, or it can determine the difference between screws and bolts from the screw hole position and change the tightening torque by itself.