Wednesday, 30 December 2015

The Pneumatic Torque Wrench: Advantages And Applications

A pneumatic torque wrench is a very useful tool. Its essential purpose is to allow the application of a very specific amount of twisting force to a particular object, usually a fastener like a nut. This can be useful for a variety of reasons. Torque wrenches are handy for when you want to avoid tightening something too tightly if there is a risk of breakage or in case it will become too difficult to remove afterwards. They are also useful in ensuring that something is tightened enough to be safe and reliable. In this article, we will discuss wrenches that are controlled by air pressure in more detail and consider their uses and their applications.

Compared To Other Torque Wrenches

The pneumatic torque wrench uses compressed air for its drive. There is a high-ratio gearbox inside that converts the fast, high-pressure flow of air into a strong, slow movement. This allows very high accuracy and can ensure that a nut is tightened to within a few percent of the target. Alternatives to the pneumatic system are hydraulic, electric and manual wrenches. Each of these will work, but none is as convenient or as versatile as the pneumatic torque wrench. Pneumatic wrenches are usually smaller, lighter and easier to use than the alternatives, and are very common in factory applications where high-pressure air is readily available.


High-performance machinery often requires very tight tolerances, not only in how carefully the parts are machined but also in how tightly they are fitted together.

 Any elaborate system of moving parts must be tightened enough that the movement is controlled and predictable but not so much that its freedom is impeded. Over-tightening can be just as damaging as under-tightening. Examples include motors and gear assemblies. A high quality wrench with a controllable slipping point allows very quick and reliable tightening to an exact torque, which ensures that the manufacturing tolerances are preserved and this eliminates guesswork on the part of the tightener.


A pneumatic torque wrench is one of the most important tools in factory settings. It allows a user to tighten fasteners by an exact predetermined amount and avoids the dangers of breaking and over-tightening. Compared to the hydraulic, electric and manual alternatives, a pneumatic system is clean, simple, lightweight, reliable and easy to use, making the air-controlled wrench the best option when you need fast, accurate and efficient tightening for any application, whether for DIY or in large-scale industrial settings.

Tuesday, 22 December 2015

Difference Between Torque Wrench and Tensioners

Torque wrenches and bolt tensioners are two of the most common means of tightening large bolts, where high bolt loads are required. Proper bolt tightening is critical to the operation and safety of most mechanical devices. Generally speaking, the heavier or more powerful the piece of equipment, the greater stress the bolts are put under and the more important that the bolts provide sufficient clamping force. In the case of large bolts, hydraulic wrenches, or tensioners are needed to tighten bolts sufficiently to create adequate clamping force.

Bolt Theory

In order to understand the difference between torque wrenches and tensioners, we must start with an understanding of the theory behind bolt operation. These simple mechanical devices operate by providing clamping force to hold two objects together. While in many cases the bolt also provides support to the objects being clamped, its primary purpose is to provide clamping force.
This clamping force is maintained by the spring tension that is inherent in the tightened bolt. In the process of tightening the bolt, it is stretched microscopically. The elasticity of the material used in the bolt’s manufacture causes it to want to return to its original unstretched shape. This spring tension causes the clamping force and together with the friction in the bolt’s threads, works to prevent loosening.
So, ensuring proper clamping force and the maintenance of that clamping force is a function of ensuring that enough spring tension is created in the bolt while tightening it. Both torque wrenches and bolt tensioners work to create this spring tension by stretching the bolt. However, they use different means to accomplish it.

Torque Wrenches

Torque wrenches provide this tension by the amount of rotational force they apply to the bolt. As the force is applied, it the threading draws the nut face and bolt head closer together, stretching the bolt and creating the clamping force. This is the most common form of providing load to a bolt. For high clamping force a large amount of torque is needed; hydraulic wrenches can provide this force.
With hydraulic wrenches, torque is controlled by the hydraulic fluid pressure. The higher the pressure, the more torque is applied to the bolt. As hydraulic fluid doesn’t compress, this provides very accurate and consistent torque values.

Torque has been used as a means for controlling bolt loading and clamping force for many years. Therefore, there are standard torque tables available, which provide guidance for determining the correct amount of torque to be used for a particular size and grade of bolt. For the greatest possible accuracy when specifying torque for a particular application, it is important to take into consideration a number of other factors, all of which can affect the amount of clamping force that a particular amount of torque applies. 
  • The finish used on the bolts
  • Whether or not flat washers are used
  • The number of times that the bolt has been used
  • Cleanliness of the bolt
  • Whether or not a lubricant has been applied to the threads and nut face

Bolt Tensioners

Bolt tensioners work by preloading the bolt, stretching it before the nut is installed. The tensioner is clamped to the bolt’s threads and pushes against the flange in the surface being bolted. This provides a very consistent amount of stretch to the bolt, ensuring consistent bolt stretch and clamping force.

The drawback to bolt tensioners is that they must be selected specific to each application. Much more data must be compiled and considered in the selection of a tensioner; this includes:
  • Bolt diameter
  • Free stud protrusion length
  • Nut size
  • Washer thickness and diameter
  • Bolt grade
  • Bolt load requirement
The amount of bolt stretch is controlled by the hydraulic pressure applied to the tensioner. Since the bolt will be pre-stretched by the tensioner, minimal torque is needed to tighten the nut onto the stud. The necessary clamping pressure or bolt load is accomplished by release of the tensioner, allowing the natural elasticity of the bolt to provide the clamping pressure.


Spirited discussion still rages over whether torque wrenches or bolt tensioners are the better means for tightening heavy bolts to produce high bolt loads. Both tools have their advantages and their disadvantages. It is important to use the method recommended by the manufacturer of a particular piece of equipment, whether torque controlled hydraulic wrenches or tensioners, in order to ensure that the bolts are properly tightened for that application.