What Is an Electric Torque Wrench?
An electric torque wrench (nutrunner) is a tool capable of semi-automatic fastening of bolts and nuts with specified torque.
It plays the role of an electric socket wrench and an electric torque wrench at the same time. It can tighten bolts and nuts at high speed with the specified torque, thus dramatically improving the efficiency of work.
There are four main types of electric torque wrench: those that can set the torque applicable to the target bolt or nut, those that manage the tightening torque by angle, those that manually stop operation when the specified torque is reached, and those that automatically tighten to the temporary tightening torque and then manually tighten to the specified torque.
Uses of Electric Torque Wrenches
Electric torque wrenches are used on sites where work speed is required, as well as for high-torque fastening applications that are difficult to tighten manually.
For example, the specified torque for ISO 10-hole wheel nuts for large vehicles is as high as 600 Nm. In the case of 3-axle vehicles, 60 nuts must be tightened for 6 wheels, which is a considerable burden on the operator.
In addition, when constructing transmission line towers or wind turbines for wind power generation, the work is performed at high places, and there is a risk of losing balance and falling down.
Electric torque wrenches are equipped with a support mechanism that catches the reaction force and prevents stress from being generated in the part operated by the operator, thus enabling safe and efficient tightening to the specified torque.
Principle of Electric Torque Wrenches
Electric torque wrenches are suitable for nighttime work or work in residential areas because they do not generate impact noise like impact wrenches.
In addition, the low vibration of the wrench reduces the physical burden on the operator, and reduces the risk of vibration-induced carpal tunnel syndrome and carpal-arm vibration syndrome. The risk of developing noise-induced hearing loss is also reduced, contributing to the prevention of occupational accidents.
Some products can be connected to a computer to manage the work itself. By recording and storing data on “which bolts and nuts were tightened and at what torque,” it is possible to prevent accidents caused by forgetting to tighten them and to check the work procedures.
Although this system has many advantages, it has a disadvantage of limiting the size of the work area and storage space, because it requires the use of a wrench hanger with a damper to support lifting when using a large electric torque wrenches.
Small Electric Torque Wrenches
Small electric torque wrenches are often used hand held and are often battery rechargeable. The rechargeable type has the advantage of having no power cord, so there are no restrictions on work operation or placement. Also, many models have a function that allows wireless communication with a host for torque management, which is required for electric torque wrenches, and even battery-powered wrenches can transmit measured data and receive control signals. This function can also be used with corded models, allowing for centralized data management in the factory. In addition, the risk of running out of charge is reduced by using the same type of battery throughout the factory.
However, compared to electric and rechargeable impact drivers, these wrenches are larger, heavier, and have a lower rotation speed, so they must be used in different ways, depending on the application.
Torque Management of Electric Torque Wrenches
Electric torque wrenches operate by monitoring the torque, angle, and speed changes during tightening.
The records can be stored in the electric torque wrenches itself or wirelessly transferred to a host for management as assembly result data. These functions can also be used to determine if a bolt is tightened properly. For example, this is because the torque data can detect such problems as diagonal tightening where bolts are inserted at an angle, omitted insertion of washers, and double insertion.
In addition, the advanced models can detect the posture and position of the electric torque wrenches, determine the position of the screw tightening hole, and determine whether the screw or bolt being tightened matches the specified one or not. The tightening torque can be automatically changed by determining the screw or bolt specification from the screw hole position.
Sockets for Electric Torque Wrenches
Sockets used with electric torque wrenches are sold exclusively by each electric torque wrench manufacturer. Basically, the same sockets for general-purpose socket wrenches or impact wrenches can be used. From the viewpoint of torque management, it is necessary to use sockets with high mounting accuracy.