What is a torque multiplier? What is a torque multiplier for?

As the name suggests, an appliance doubles the torque. It is a torque tool that can be used for the disassembly and assembly of bolts and nuts and can control the torque. It is a labor-saving tool. It has a variety of names, such as torque multiplier, torque amplifier, force multiplier, manual torque multiplier, etc.

What principle does the torque multiplier rely on to amplify the torque? What are the types?

At present, the torque amplifier on the market basically adopts a gear transmission reduction structure, which is essentially a reduction gearbox. There are two types of plate type and column type, no matter which type, it needs to be used with the reaction arm. The reaction arm can be a body or an external one, so when using it, you need to find a reaction support point for the torque amplifier. Also, as the torque increases, the angle of rotation increases proportionally because energy is conserved. For example, in a torque amplifier with a gear ratio of 1:4, the input end rotates 4 turns, and the output end can only rotate 1 turn.

The principle and application of the plate torque multiplier: the plate torque multiplier is also called the torque transmission plate. Its appearance is somewhat similar to the hollow hydraulic torque wrench, and its transmission mode is fixed shaft gear transmission.

It is composed of 2 or more gears, eccentric design, and the input and output are not concentric. The torque transmission plate is mostly used in conjunction with electric and pneumatic torque wrenches to solve the working conditions with limited space.

It is basically a customized product designed according to specific working conditions, and it is used less and is not common.

Introduction to the principle and application of the cylindrical torque multiplier: The cylindrical torque multiplier is widely used, and adopts planetary transmission. Each planet includes sun gear, a planet carrier, multiple planetary gears, and an outer ring gear. Among them, the input end is integrated (or connected) with the first sun gear, and the input end generally adopts the ISO standard 1/2″ or 3/4″ inner square. The output end is integrated (or connected) with the last planet carrier, generally using the ISO standard 3/4″, 1″, 1-1/2″, or larger outer square, which is used in conjunction with the sleeve.

There are single-section, 2-section, 3-section, or even more. Under normal circumstances, the more planetary sections of this multiplier, the greater the multiplication ratio and output torque. Structurally, the single-section planetary manual torque increaser is generally not equipped with an anti-rotation ratchet mechanism, and the 2-section and multi-section planetary torque multipliers must be equipped with an anti-rotation ratchet mechanism.

Because the column torque amplifier is widely used and has strong versatility, the following discussion is based on this multiplier.

How to choose a torque multiplier? What are the important parameters? What are the specifications?

As a precision bolt disassembly and assembly tool, torque amplifiers should refer to two important parameters when selecting models: maximum output torque and torque multiplication ratio.

Considering the durability of the tool, it is recommended to leave a mechanical margin of about 20%. If the actual use reaches 2500Nm, it is more appropriate to choose a 3000Nm torque amplifier.

The torque multiplication ratio is the ratio of input and output torque. For example, a torque amplifier with a multiplication ratio of 1:10 means that the input terminal inputs a torque of 250Nm, and the output terminal outputs a torque of 2500Nm.

After these two parameters are determined, select the appropriate manual torque increaser model with reference to the use of space, multiplier accuracy, outer diameter, length, weight, and other parameters.

There are many torque specifications of torque multipliers, ranging from hundreds of Nm to tens of thousands or even hundreds of thousands of Nm, but torque multipliers with a torque range of 1200Nm-15000Nm are most commonly used.

Can a torque multiplier precisely control the output torque? How accurate can it be?

The torque multiplier is used in conjunction with a manual torque wrench to realize the constant torque disassembly and assembly of bolts and nuts. When used in conjunction with an ordinary ratchet wrench, it cannot achieve precise control of the output torque. Only quantitative output is possible because of quantitative input; torque multipliers on the market generally have a nominal accuracy of ±5%.

What determines the output accuracy of the torque multiplier?

This is relatively complicated. Of course, the most direct determinants must be the rationality of product design, the manufacturing accuracy and assembly accuracy of gears and other components, bearing accuracy, heat treatment quality, and materials.

As a manually operated torque tool, the actual torque output accuracy of the torque multiplier is not only closely related to the accuracy of the torque amplifier itself, but also to the accuracy of the manual torque wrench used.

The final torque output accuracy is also very dependent on the operator’s operation. In general, the comprehensive output accuracy of a high-quality torque amplifier can reach ±5%.

Is the torque multiplier gear ratio the same as the multiplier ratio?

On this point, there has always been a misunderstanding. Many people think that it is the same. In fact, it is not. The former is slightly larger than the latter. Why?

Because the torque amplifier is essentially a kind of gearbox, similar to the automobile gearbox, there will inevitably be losses during the transmission process. The single-section planetary efficiency of the high-quality manual torque amplifier can be about 95%.

What are the features of a torque multiplier? For which occasions is it suitable?

As a manually operated torque tool, the torque multiplier has advantages and disadvantages:

Torque Multiplier Advantages:
1. Manual operation, not affected by the power source.
2. Small size, lightweight, and easy to use.
3. The torque can be preset accurately to realize the precise assembly of bolts.
4. Effort-saving, easy to achieve large torque output.
5. Compared with the electric constant torque wrench, pneumatic constant torque wrench, and charging constant torque wrench, the price is low and economical.
6. Durable.

Torque Multiplier Disadvantages:
1. Manual operation, low efficiency, unable to achieve mass bolt assembly.
2. The output accuracy is greatly affected by the operation methods and habits of different operators.

Application of torque multiplier: High torque operation is required, but the on-site space is limited, or there is no electricity, no compressed air, etc., so the electric torque wrench and pneumatic torque wrench cannot be used. Or the number of bolts is small, considering the cost, the use of torque multipliers is a practical, economical and effective solution! Such as field equipment maintenance, after-sales of construction machinery manufacturers, flammable and explosive chemical industry, spot inspection and maintenance of wind power equipment, etc.

What are the prices and market conditions for torque multipliers? How to choose?

At present, there are many brands of torque multipliers, but the quality is uneven, and the price is also huge.

Therefore, it is quite difficult to choose a high-quality and affordable torque multiplier. When choosing, be sure to keep your eyes open, and try to choose a professional manufacturer, otherwise, it will be embarrassing when the product needs maintenance.

From the perspective of taking into account the operating space and efficiency, try to choose a torque multiplier that can achieve the maximum torque output when the input is about 300Nm.


Because the 300Nm manual torque wrench is of moderate length, the output torque of 300N is not particularly laborious, and it can also take into account the efficiency. The larger the torque ratio, the more turns are required at the input end.

Precautions when using the torque multiplier.

1. It is necessary to understand the maximum output torque and torque ratio of the torque amplifier, which are two very important performance parameters of the torque multiplier.

2. The torque multiplier is a torque tool with a reaction arm, and the huge torque generated is absorbed by the reaction arm. Therefore, it is necessary to find a support point of sufficient strength for the reaction arm during the operation, and any part of the body should be kept away from the working range of the reaction arm.

3. Be sure not to use power tools (especially impact type) to drive the torque amplifier, otherwise, the transmission system will inevitably be damaged. It is recommended to use it in conjunction with a manual torque wrench, and it is not allowed to input more than the specified upper limit torque.

4. The torque amplifier is a precision torque tool. Before each use, be sure to check whether the output square head, reaction arm, and other components are in good condition and the accuracy of the matching manual torque wrench.

5. After the locking nut is completed, the torque amplifier cannot be removed directly. Appropriate torque must be applied in the locking direction, combined with the reversing button and the reversing push rod, to complete the reversing of the anti-rebound device. At this time, be sure to hold the handle of the manual torque wrench tightly and slowly release the internal stress of the torque multiplier to avoid injury caused by the huge rebound force of the gear system.

Maintenance of the torque multiplier.

Torque multipliers are essentially planetary gearboxes, so maintenance is essential.

Every six months or 20,000 times of use, it is recommended to maintain the gear transmission system and replace it with new lubricating grease.

It is recommended to use grease with penetration and grade of 265-295 and a viscosity grade of 2. High-quality grease can not only maximize the performance of the machine but also prolong the service life of the product.