A torque wrench is a universal and widely used tool when it comes to cars, machinery, equipment, and construction. For simple work, an ordinary wrench will do, but for more complicated and delicate tasks torque wrenches with the possibility to set and measure the torque are applicable.
Professionals can easily tell the difference between various types, use and read them, but for inexperienced users, the gear is a huge challenge. Which type to choose? How to adjust all the needed parameters and how to read the real torque applied to the piece of machinery? Let’s try to sort out all this.
Table of Contents
What is a torque wrench?
A torque wrench is intended to tighten up nuts and bolts with preset torque indications. If you overtighten the piece, you’ll damage the threads on the bolt. In the opposite case, if the torque power wasn’t enough, the piece will be unsafe and come off with use, and your equipment can break down, fall apart, or even cause accidents.
To prevent these both undesirable outcomes you must control and be confident in the applied torque level. Get acquainted with the scales, and units. The most spread types are micrometer, beam, dial wrenches, and a cutting-edge digital torque tool.
How does this tool work?
A torque wrench has a shaft with figures printed on it. The rotating handle moves forward and backward at the end of the shaft. Inside, there is a screw thread, along which this handle moves. The screw thread has a definite pitch, which corresponds to the torque level set outside.
When the handle of the torque wrench travels forward, it compresses the spring coils. The further the handle goes, the tighter is the compression on the coils. As you loosen, rotating the handle backward, the distance between the coils of the spring increases. That’s how the strength of the spring inside the shaft of the spanner is translated to the setting of torque outside. This makes reading and adjusting possible for you.
A micrometer torque wrench and how to read it
To understand the principle of work of a micrometer torque wrench follow a few uncomplicated steps.
Step 1 – Turn the knob
To start the work turn the knob anti-clockwise. The cap, located at the bottom of the handle, loosens the torque wrench and allows you to rotate the gear for the torque setting adjustments.
Step 2 – Look at the scale
Find vertical figures located above the handgrip of the torque wrench. The first set of numbers is in foot-pounds or abbreviated to ft.-lbs. and the other one is in Newton-meters or Nm. These two units are commonly and equally used to determine the torque level. The vertically printed numbers are referred to as the main scale with horizontal lines for more comfortable use. They show the torque settings of your wrench in the tens: 10, 20, 30, 40…
Step 3 – Find the micrometer around the handle
The digits running around the wrench’s handle are known as the micrometer. They define the second half in the torque measurement and help adjust a more precise torque regulation.
Step 4 – Rotate the handle on the tool
To place the torque just rotate the handgrip. If you want to raise the torque value, turn the handgrip clockwise, and the opposite action, anti-clockwise, will decrease it. When rotating the handle moves up and down simultaneously with the micrometer figures. Both the main and micrometer scales figures change with rotation.
Step 5 – Adjust the required settings
Make sure the vertical line on the wrench handle coincides with the vertical numbers on the micrometer to receive an accurate setting. A torque setting is read by adding together the two figures: of the main scale and micrometer. Let’s say, the main scale is a little above the 60-ft.-lbs. and the 5 on the micrometer coincides with the vertical line. In this case, your wrench setting is 65 foot-pounds.
Step 6 – Tighten the knob
The knob must be tightened to finish the torque setting of the instrument. Rotate the knob clockwise. This way you fix the position and the level of torque applied. If you have to change the adjustments, first weaken the knob and repeat all the steps from the start.
Step 7 – Be attentive to hear a warning click
When you use the wrench, wait for an audible click, which will signal about reaching the preset torque level. After that sound don’t tighten anymore! To prevent tension on the wrench mechanism use the lowest torque setting for storing it.
Practical tips and examples of reading the gear
Always check the needed level of torque with item descriptions or instructions manual.
Remember about two scales: the main one and the Micrometer. On the left-hand side you can see the printed odd multiples of ten – ten, thirty, fifty, seventy, and on the other side the even multiples of ten – twenty, forty, sixty, eighty foot-pounds. The torque is settled by using a couple of reference lines.
A setting is read with a rotating Micrometer scale, which has numbers going from 0 to 10. Although, we actually look at 0 2 4 6 8, and again 0 is instead of 10. So a torque setting is read by adding multiples of tens on the left side or the right side and the ones digit from the rotating handle.
The intersection of the handle lines up with the intersection of approximately the nearest tens amount, an obvious vertical stripe in the middle. For example, the torque is exactly ten foot-pounds. As you rotate the handle forward, you set to eleven foot-pounds – the tens amount again comes from the main scale and the ones digit comes from the Micrometer. At this moment the one is aligned.
The next reads as 20 foot-pounds because the nearest ten above the handle is 20, as the 10 is covered up halfway. The zero in the middle corresponds to and lines up with the vertical stripe on the main scale.
Let’s set the wrench to 26 pounds. How does it look like? 26 foot-pounds would be past the 20 and the 6 aligning with the mainline on the main scale. The vertical stripe on the main scale reads 26 pounds because 20 is a whole number that was passed and 30 foot-pounds haven’t been reached yet.
Now try to set it to 32 pounds just rotating forward up to 30 and rotate the handle a little more. Now it reads as 32 foot-pounds of torque because the 30 is exposed above the handle, and on the handle, a number 2 is lining up with the main vertical stripe on the main scale.
In terms of physics, there is a general confusion about mass and weight. Those are different things but, fortunately, regarding torque, foot-pounds are just as good. At the back of the wrench, we have Newton-meters.
Interpretation of the figures on a beam or dial torque wrenches
Find the meter
You can easily notice a scale in the lower part of the torch wrench with an arrow and figures. The figures correspond to the torque level in foot-pounds and Newton-meters. The arrow points the torque, which is applied to a bolt or nut. The static position should be read as zero.
Keep an eye on the arrow
When you work with such torque wrenches be careful with the effort taken to tighten a bolt or nut. During the work the arrow moves, showing the quantity of torque you’re using. Be slow and control the level of torque, if you don’t want to damage the bolt. Look down straight at the arrow to read the torque accurately.
For convenience, a few dial torque wrenches can boast of a memory arrow. It follows the main arrow and represents the maximum level of torque been applied to the nut. Even after disengaging the wrench you can see that indicator.
Stick a piece of tape
Apply tape on your required torque line for easy and comfy reading. Due to lots of stripes and figures on a beam or dial torque wrench, the reading can be uncomfortable without the mark. In case a memory arrow is absent, stick a piece of tape near the stripe of the needed or maximum torque value. Making a mark facilitates reading the wrench.
A modern digital torque wrench – setting and reading
Take the user’s manual
Use the instructions coming with the digital torque wrench to find out how the settings are adjusted on the wrench. Additionally, follow all the tips to adjust and understand the measurement units in foot-pounds or Newton-Meters.
Set the torque using the up and down arrow buttons
Push down the up and down arrows to customize the torque setting requirements on your wrench.
Adjust the tolerance parameters
For precise torque the % button sets the tolerance. Most models of digital torque wrenches include tolerance parameters for your convenience when you perform high-precision tasks. These indicators warn that your wrench reaches the preset level of torque.
If the tolerance parameters are 50% the wrench warns with light and vibration, that you’ve reached 50% of your needed torque. Hit the % button to start setting the tolerance parameters, and push up and down arrows to choose the desired percentage.
Modify the sounds and vibration effects, if needed
A few models of digital torque wrenches have additional settings of sound and vibrations, produced by the gear. Customize the effects for clear comfy usage and great results.
Prepare the pieces
Cleanse the threads of the bolt, you are going to torque but forget about lubricants or tapes. They aren’t recommended for this job.
Make the torque corrections for extensions
Calculate the torque carefully and make necessary changes if you work with any additional parts, such as extensions, or adapters. Keep in mind, that 1 ft-lb must be added per 1 inch of extension.
Stop working after a signal
When the wrench lights up, vibrates, or produces a warning sound it means you’ve reached your goal – the level of torque you want. Stop turning the nut after this notification.
Reading the torque wrench is simple when you have an idea about how it works. General understanding of working principles, the scale and units will help, but learn to adjust the settings, and you will never be mistaken.
Good luck and easy work with your torque wrench!