A wrench is a wrench is a wrench, right? Looking through the tool department at the hardware store can make for a very confusing time. So many choices, sizes, shapes and mass confusion for any shopper that doesn’t know what they are looking for. There are umpteen tools and double umpteen wrenches out there. So what in the world is a torque wrench?
What is a torque wrench? A Torque wrench is a tool used to apply a specific torque, or rotational force, to a fastener such as a nut or bolt. Torque is the measure of how much force on an object causes it to rotate, with the pivot point being the axis the object rotates on. Torque is measured in either lb*ft (pound/foot), lb*in (pound/inch), or N*m (Newton meter). It is usually in a socket wrench form with special internal mechanisms.
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When Do You Need A Torque Wrench?
A torque wrench would be used when the tightness of the screws or bolts is crucial. It lets the operator set the torque applied to the fastener so it can be matched to specifications for a particular application. This allows for proper tension and loading of all parts. A torque wrench uses torque as a proxy for bolt tension.
A torque wrench is calibrated to apply a specific amount of torque to a fastener. The amount applied depends on the amount of force on the tool’s handle and the length of the wrench. To work out the required torque there is a formula. Force x length = torque.
If the nuts and bolts that secure a replacement part or mechanical system require a specific torque pressure, a torque wrench is required. If you attempt to use a manual or impact wrench, a couple of things could happen.
- The fasteners would be too loose. If this happens, there will be a gap between the nut and bolt and the part you are trying to secure. When this happens, too much heat builds up and it loosens the fastener and causes the bolt to snap or the part falls off. With wheels, steering or braking this could be a serious problem, causing accidents or worse.
- The fasteners could be too tight. Most people don’t realize how strong they really are, which is why tightening too much is actually more common than leaving it too loose. When they are too tight, there is too much force, which can warp, bend or damage the bolts or the parts themselves.
Both of these circumstances are dangerous, which makes it even more important to identify when a torque wrench is the tool for the job.
Type Of Torque Wrenches
Based on the project at hand you may need a specific type of torque wrench. Let’s dig into the details on what the different types of torque wrenches are and when you would need to apply the specific type.
Different types of torque wrenches include:
- No-Hub Wrench
The beam torque wrench is generally inexpensive and easy to use. It is the most basic form of torque wrench and has two beams. The first is the handle and is used to apply the torque to the fastener being tightened. The second beam is only attached at one end to the wrench head and is free on the other. Both these beams run parallel to each other when the tool is at rest, with the indicator beam on top. The indicator beam’s free end is free to travel over a calibrated scale attached to the lever or handle, marked in units of torque. When the wrench applies torque, the lever bends and the indicator beam stays straight. The end of the indicating beam points to the magnitude of the torque being applied. These tools can be used for tightening or loosening. A beam torque wrench is used mostly for automotive maintenance and repairs.
A slipper type torque wrench has a roller and cam mechanism. The cam is attached to the driving head, the roller pushes against the cam locking it into place with a specific force provided by a spring, which can be adjustable. A slipper torque wrench will not over tighten a fastener by going beyond a predetermined limit.
A click torque wrench gives an audible sound when the appropriate torque setting is reached. This wrench has a spring loaded lever that is adjusted by twisting the handle to the correct setting. Once the setting is reached, it simply clicks and releases. Most of these are of the ratchet style and can be used for tightening or loosening. A click torque wrench is used for both industrial and automotive projects.
A no-hub torque wrench is a specialized torque wrench used by plumbers to tighten the clamping bands on hubless soil pipe couplings. These are usually T-handled with a one-way combination ratchet and clutch. These tools are preset to a specific torque so they secure the coupling, but don’t damage it. No-hub torque wrenches are used frequently in the plumbing industry on pipe couplings.
A dial torque wrench is considered one of the most accurate of torque wrenches. They are also wider than most of the others, so they are more difficult to use in small spaces. The dial torque wrench is used quite often in the automotive, aerospace, and defense industries.
A micrometer torque wrench is most often used in the manufacturing and transportation of cargo. When transporting freight or cargo by plane, train, or ship, knowing the weight of the cargo is vital because the weight may change the distribution of the cargo. This tool will help monitor it properly to keep the crew and cargo safe.
Hydraulic wrenches are used most often in the industrial arena and are used for tightening large torques with high accuracy. They are designed to reach the required torque with the use of hydraulics. Usually they consist of at least one hydraulic cylinder operating a drive head ratchet.
Electronic torque wrenches are sometimes called digital as well. They don’t have any moving parts and work from an electric sensor. They can sense how much twisting force is being applied and lets the user know on a digital display. These tools have small chips in them which contain a memory stick that saves readings and can be accessed on a computer. These torque wrenches are often more accurate, but they are also more delicate due to their construction.
Storing A Torque Wrench
The torque wrench isn’t your everyday type of tool and shouldn’t be treated as such. If you are using your torque wrench regularly, there is no need to for it to be wound back. If you are storing your torque wrench for longer periods of time, you should always wind it down to the minimum scale setting, but never to zero.
If you store your torque wrench fully loaded for a long period of time, it can cause a set in the spring and it will weaken over time. In the other direction, if you set it to zero, other components within the wrench could move even just a little. If this happens, when you apply spring compression the orientation of the components can change and affect the accuracy. For this reason, it is best to leave at least some compression in the spring while storing your torque wrench.
Calibrating A Torque Wrench
In order to keep your torque wrench reliable and giving accurate, precise measurements, it is important to calibrate it regularly. Calibrating is a procedure that checks the accuracy of an instrument. It is recommended to calibrate the tool every 5000 uses or once a year and to have it done by a professional.
Not calibrating your torque wrench can be dangerous. It can lead to pipe or equipment failure. If your wrench isn’t calibrated, then it isn’t working properly and the nuts and bolts you are tightening may not be tightened properly.
What is the difference between a torque wrench and a ratchet? A socket set is needed to use a torque wrench. Torque wrenches can be used on any bolt that needs to be tightened to a specific setting, but they do not have a ratcheting mechanism. Therefore, a ratchet is used to tighten the bolt and the torque wrench is used to apply the final torque.
Do you really need a torque wrench? If you plan on doing any major work on your engine or some major powertrain components, you absolutely do need a torque wrench. Over tightening cylinder-head bolts, for example, can cause severe damage and coolant loss, and be extremely costly.
Is it ok to use a torque wrench to loosen? As long as you are careful and do not use the maximum torque, most torque wrenches can be used to loosen. If the bolt cannot be loosened within the maximum torque, another tool should be used instead. If in doubt, use another tool.