How to choose the right torque wrench?

How to choose the right torque wrench?

Purchasing a new tool for the workshop can sometimes seem like a simple and straightforward decision. However, comparing brands, product features and the application you require the tool to perform can sometimes add confusion into the decision making process. When it comes to making a purchasing decision, many factors are taken into account such as - Price - Quality - Product Features - Ease of Use - Durability All of these aspects basically lead the purchaser to choose the best "Value for Money" product. Every consumer, whether they are buying a car, a house or a tool, all expect value for money and rightly so. Therefore buying a tool that is not quite right for the job or that doesn't perform to the high standard that you expect, will ultimately prove to be an unhappy purchase. One of the most commonly used tools in the automotive service industry has been the torque wrench. Along with a spanner and socket set, there is not one workshop that does not have at least one or more torque wrenches being regularly used. In summary, a torque wrench is a tool that allows the user to control the force or torque that is applied while tightening or loosening a bolt.

A torque wrench will usually have a gauge indicating the amount of torque applied in the activity to ensure that the nut or bolt is not under or over torqued. Torque Wrenches are designed for a variety of applications for both Automotive and Industrial use. Sizes and capacity range from small, medium and large. The torque range for a small size models is generally anywhere from 30-200in. lbs. (4-22Nm) with either a ¼" or 3/8" square drive. This size wrench is suitable for everyday use with low torque applications and are a widely used for transmission servicing. For medium size models, torque low range will be anywhere from 20 or 30 ft lbs. (17 or 34Nm) with a torque high range of approximately 250ft lbs. (332Nm) and are usually supplied with ½" square drive adaptor. These are a good option for engine rebuilding and reconditioning applications. Even larger capacity wrenches which have a range of up to 1000 ft.lbs (1320Nm) are also available for heavy automotive and industrial use such as truck, machinery and heavy plant maintenance. When it comes to torque wrenches or any tool for that matter, certain factors can at times be overlooked which will determine whether a wise buying decision will be made. The longevity and durability of the tool is one of the ultimate tests in determining a "Value for money" product. For example, How long will the product last? Will it last 1 or 2 years or will it last 20 or 30 years and will it be something that can be passed on to the next generation? Will the torque wrench be as accurate after 500, 1000 or 5000 uses as it was on the first use? What will the total cost of ownership be for a torque wrench when regular calibrations and repairs are taken into account? In terms of quality, one important aspect is to verify the torque wrench performance against Australian or International standards for accuracy.
 
Most models have an accuracy tolerance for the displayed torque output. For example, some makes and models have a tolerance of +/- 4%, +/- 2% or even +/- 1%. The lower the tolerance the more accurate the reading will be as the true reading will be within the specified + or percentage of tolerance. In order to assist in the decision making process, we have put together a review of some of the various types of torque wrenches that are available in the market place in order to assist you in making the correct decision.  
 
Torque Wrench types Deflecting Beam Torque Wrench
With a tried and tested design from Australia that has been around for over 50 years, the deflecting beam torque wrench has proven to be a tool that is handed down from generation to generation. They work by applying torque to a deflecting beam rather than a coil spring which prolongs the life of the wrench and also ensures extreme accuracy. A dual signal feature (visual and audible) ensures that operator knows when the desired torque has been reached. A disadvantage is that it does not contain a ratchet head which some may prefer and the majority of models can only be used in one direction for tightening nuts or bolts. However, by attaching products such as ratchet adaptor or a torque-angle adaptor to the deflecting beam torque wrench, certain obstacles can be overcome and the wrench becomes much more versatile. The deflecting beam torque wrench has a simple design with proven results and reliability. It is a product that will maintain its accuracy over the long term due to it containing no wearing parts. Check to see if the product you are purchasing is an Australian made original or an overseas imitation.
 
Micrometer Torque Wrench
Perhaps the most commonly used and most versatile torque wrench, which you will find in any mechanical workshop is the Micrometer Torque Wrench. The torque setting is simply adjusted by twisting the handle until it reaches the correct torque setting on the barrel of the tool. Rotating the handle clockwise tightens a spring inside and when you apply torque to a nut or bolt, the tool clicks to let you know the correct torque has been reached. One of the major benefits of the Micrometer wrench is its ratchet function for either Left or Right hand operations. They feature a distinct breaking action when the set torque is reached. The automatic reset feature ensures that the wrench will automatically reset itself after use by removing load on the spring and ensuring that it is ready to operate again. It's sturdy and robust design make it an ideal tool for everyday use. One of the disadvantages is that due to force being applied to wearing parts such as an internal coil spring, they require regular re calibration. Depending on brand and place of manufacture, quality and price can vary from the cheap and nasty through to the professional high end. Caution must be taken with the Micrometer wrenches as you will generally get what you pay for. Cheaper models can easily go out of calibration very quickly.  
 
Dial Type Torque Wrenches
Dial-type torque wrenches are generally considered to be one of the most accurate types of torque wrench. The dial-type wrench is the only type of torque wrench where the final reading is not easily affected by the hand-hold position on the wrench. Dial Type torque wrenches are wider than some of the other types so may be difficult to use in tight situations, and the dial scale must always be in sight to determine the torque being applied. Dial type wrenches are generally more expensive than other types of wrenches however they are extremely accurate. In addition to automotive use they are also used in the aerospace and defense industries.
 
Electronic / Digital Readout Torque Wrenches
Electronic or Digital torque wrenches have a digital readout screen which allows the user to program the torque limit. A strain gauge which is attached to a torsion rod sends a signal to a transducer to determine the force of torque per unit, which is then displayed via the LED reading. The LED lights will notify the user when they are approaching a desired torque setting and when the torque setting has been reached along with an audible alert signal. Some models also have an internal computer chip which allows torque measurements to be saved and then downloaded to a database for record keeping. This is also beneficial for any auditing requirements. Electronic or Digital wrenches have come down in price over the last few years and are now much more affordable and accessible for most automotive mechanics. However, many users find that the new Torque and Angle wrenches do exactly the same function with the added benefit of angle readout for torque to yield applications.
 
Torque-Angle Torque Wrench
Torque-Angle Torque Wrenches are used for torque to yield applications which are specified predominantly for cylinder head bolts but also for main bearing caps and suspension components. Torque to yield bolts require correct sequence tightening which is essential to eliminate distortion. Torque is further applied in sequence through a series of motions, only this time instead of torque load being measured, angle of rotation is also measured. A Digital Torque Angle wrench works in a similar way to a standard Electronic Torque wrench with the additional feature of applying angle rotation to a nut or bolt. The wrench also contains a digital readout and a function screen which allows the user to easily program the required torque and angle setting. The user then applies the required torque value and any additional angle rotation. Some models allow this function be performed in one continuous motion, without having to stop and reprogram the wrench. LED lights and an audible warning sound notify the user when the correct settings have been reached. Torque-Angle Torque Wrenches are now widely available through most tool distributors and a good quality wrench will retail from $350 and upwards. Make sure the wrench you choose allows you to apply torque and angle in one continuous motion, which will make your job much easier.  
 
Detachable / Interchangeable Head Torque Wrenches
One of the new Torque wrench products on the market, the Detachable Head Torque Wrench is generally supplied in a kit with a standard ratchet head and a variety of open end adaptors. The heads are all detachable which allows the wrench to be used as a standard Screen Wrench or an open end torque wrench. Different size open end heads are usually supplied in the kit. The term Screen refers to Convex screen which magnifies the torque scale on the handle. The Detachable Head Torque Wrench is a very cost effective tool that gives you so much for your money. As well as being supplied with a detachable ratchet head, the addition of the open end detachable heads in various sizes to the kit means that this tool is suitable for many applications including accessing nuts and bolts in tight areas.  
 
Conclusion
There are many other types of torque wrenches which are used in the market however we have addressed the vast majority and most commonly used torque wrenches. Other types including Hydraulic Torque wrenches where heavy loads of torque need to be applied and as well as other variations to beam wrenches and Screen torque wrenches are also available in the market. However, when deciding on the perfect tool to use you first need to determine which tool will best suit the application that you require it to perform. In regards to torque wrenches on the market, there are so many different types that vary in function, accuracy and durability. Remember, a torque wrench is a precision instrument and it is worth investing in a quality product. Therefore, investing in a quality torque wrench will certainly prove to be the wisest choice, as you will get a tool that is accurate, durable and guaranteed to last many years.