When installing electrical equipment you’ll be required to use a torque wrench. A torque wrench is a special tool used to tighten nuts and bolts to a certain specific torque so that they do not stretch, break or become loose.
Manufacturer’s of electrical equipment require all screws, nuts, bolts, and connections be torqued to their specifications. It is specially calibrated to measure the amount of force applied to the nut or bolt that is being fastened.
This is a an easy tool to master as an electrician apprentice. You should become familiar with how to operate each and every type of torque wrench.
The wrench has a calibrated scale on which the amount of torque applied is displayed.
There are three basic types of torque wrenches commonly used today. Depending on the purpose they are meant to serve, the wrenches have different calibrations and additional tools.
The three main types of wrenches are the beam style torque wrench, the dial gauge, and the click adjustable torque wrench.
Although their sole purpose is to measure Torque, each has to be used differently. For you to get an accurate torque reading, you have to correctly use each torque wrench correctly.
Here is a quick guide on how each torque wrench for the best possible results.
Click Adjustable Torque Wrench (Ratcheting Wrench)
This type of wrench is what you’re more than likely going to be using on the job.
It has an internal spring and an adjustable handle. The required torque to be applied to the fastener is pre-set by turning the adjustable micrometer at the top of the handle.
Once the required torque is achieved, the wrench starts to click and becomes harder to turn or tighten the fastener.
They are preferred because the user can know when he reaches the desired torque without necessarily looking at the scale but feeling the resistance of the handle.
Here Is How To Correctly Use The Ratcheting Wrench:
- Unlock the handle and adjust it by turning the micrometer to the desired torque.
- Once you have the desired torque on the scale, lock the handle down.
- Connect the wrench to the socket and attach the fastener. Always ensure you use the correct size of the socket that holds on to the fastener properly.
- Apply force evenly and smoothly until you achieve the desired torque.
- Once the set torque is achieved, the wrench will start making clicking sounds. The spring will automatically snap and release the handle.
- Once you have finished using the wrench, reset the torque back to zero in order to release the pressure in the spring. Too much pressure in the spring held for too long, will reduce the ability of the spring to stretch and snap back into position over time.
Beam Style Torque wrench
The beam type wrench is the cheapest and least sophisticated wrench of them all. The beam style wrench can either have a flexible or fixed beam.
A flexible beam wrench has a pivoted handle while its fixed counterpart has a rigid beam. When you apply force to the handle, the calibrated scale deflects to the right or left to indicate the exact amount of torque exerted to the fastener.
Here Is How To Correctly Use The Beam Style Torque Wrench:
- Make sure you have the correct size socket to connect to the torque wrench. Connect the socket to the distal end of the beam torque wrench and ensure it is not loose.
- Once the socket has held on to the fastener correctly, pull the wrench smoothly and steadily. Always ensure that the direction of pull is at right angles with the handle. If the handle is flexible (has a pivot), evenly apply force to keep the handle positioned correctly at the centre of the pivot center.
- Tighten the bolt or nut until the scale reads the required torque.
When taking a reading from the wrench, always take a look at the scale from directly above it. If you read the scale from an angle, your reading will be affected by parallax errors.
You should also apply the force slowly especially when the bolt is getting tight otherwise the beam will bend. If the beam bends even slightly, replace it.
Dial Type Torque Wrench
This torque wrench is also relatively easy to use and are regarded as the most accurate torque wrench.
It measures its torque by using a needle that moves inside a vacuum dial when force is applied to it. The needle inside the dial moves both to the left and right directions.
Here Is How To Correctly Use The Dial Type Wrench:
- Attach the correct size socket and connect it to the fastener you intend to tighten.
- Hold the wrench at right angles relative to the handle of the wrench.
- Apply the force gently while tightening the bolts or nuts until the dial scale indicates the required amount of torque.
The precision of the dial type wrenches is extremely high.
If you realize that the dial indicates a reading on the scale even when there is no force applied to it, the wrench should be re-calibrated before being put to use. It is also the most expensive of all wrenches owing to its high precision.
Calibration and Units of Measurements of Torque Wrenches
The calibration of torque wrenches is different for every wrench. The calibration is normally indicated on a sticker attached to the wrench. The calibration should be re-calibrated once the expiry date is reached.
The units of measurement are different as well. The scale can either be calibrated in Inch-pounds (in.lbs) or foot-pounds (ft.lbs). Foot-pound wrenches are normally preferred for large torques while their inch-pound counterparts are used for relatively smaller torques.
Answers To Questions You Need To Be Familiar With
Can a torque wrench be used to loosen bolts? A torque wrench should never be used to loosen anything.
Can I use a torque wrench as a breaker bar? See answer above.
Can I use impact socket on torque wrench? Yes, but you can’t use a regular socket on an impact wrench. Read more here.
Can I calibrate a torque wrench? In a pinch, yes you can. But it should be done professionally. For a DIY explanation of how to calibrate watch the video below.