If you know how to use a manual torque wrench, you will get the full use out of it. Here, we will share important tips about the analog torque wrenches and how to use them effectively.
Torque wrenches are the most common tools in vehicle and bike garages today. You can buy one and keep it at home, to do DIY car maintenance tasks that require precision, and save money.
a) How to set & read a manual torque wrench
While an analog wrench is very simplistic by design, it can be hard to read and set for a first-time user. Here is how to set and read it:
How to read a torque wrench
This is the first thing to know. There are numbers and you need to know what they mean, before you can even know how to set the right torque value.
Check the wrench at a place close to the handle. There, you will see two sets of numbers. The first set has big numbers and it is on the body of the wrench. The second set has smaller numbers and it is on the handle of the wrench.
Torque is measured in different units, which helps different users to measure correctly. In this case, the larger numbers are for the metric units (meter-kilograms) while the smaller numbers are for the imperial units (foot-pounds).
The larger numbers on the body of the wrench are for the larger units (m-kg) while the smaller numbers on the handle are for the smaller units (ft-lbs).
Both the handle and the body of the wrench have hash marks. Pay attention to them because they will guide you when setting the torque.
How to set a manual torque wrench
There are two very important things to know here. First, the edge of the handle moves on the hash marks on the body of the wrench, while the handle dial twists, to set torque value.
To show you by example, if the edge of the handle rests on the hash mark for 140 on the body of the wrench and the small number on the wrench handle is on 10, the torque setting for you is 150 ft-lbs/ 20.75m-kg/203Nm.
To start setting the torque, you need to know what torque value the manufacturer recommends for the fasteners that you are tightening.
You can check the wheel lug of your car and if it does not have that indication, you can check the user manual of your car or bike.
To start setting the torque, first, support the wrench body with your left hand and with the right hand, turn the handle of the wrench clockwise or anticlockwise to raise or lower the torque, respectively.
To set the torque value at a specific number, set the handle to the hash mark that’s in the 5 ft-lb range.
For instance, to set 160 ft-lb, set the handle edge on the hash mark located between 155 and 165 ft-lb (if there is one, this is just an example).
You will do the same for wrenches that come with handles that slide up and down rather than twist.
Also note that to get the final torque value; you have to add the smaller number on the handle and the bigger number on the body.
If the handle edge is on 140 hash mark (on the body) and the handle is set on 5, the final torque is 140 + 5 = 145 ft-lb.
b) Manual torque wrench sizes
Analog torque wrenches come in different sizes. Size is important because it determines the amount of torque the tool can deliver.
Shorter handled wrenches deliver minimal torque while longer handled ones deliver higher torque.
On the other hand, manual torque wrench size can refer to the drive ratchet or socket drive size, depending on the design of the wrench.
Generally, the manual wrenches come in the same sizes as the ratchet wrenches. They start at ¼, 3/8, ½ and ¾ inches.
For higher torque, bigger socket drives and longer handles do the trick and vice versa.
It is best to buy a set with different sizes if you intend to do a variety of tightening jobs with it. Many people ask: Do I need a 1/2-inch or 3/8-inch torque wrench?
It depends on what you are doing with it. For instance, most engine tasks require the 3.8 drive. You can use it for oil pan fasteners, water pumps, cylinder head jobs and so on.
The ½ inch drive wrench is also very popular because it is used for tightening most wheel lugs (cars), engine mountings, suspension and steering parts.
As you can see, you will find some work for every torque wrench that you have in your set.
c) Manual torque wrench range
When using any type of torque wrench, it is very important that you do not exceed the recommended torque range.
To reiterate things we have already mentioned, when you are setting the torque, there are small numbers on the handle and big ones on the body. These can tell you the maximum torque range of the wrench.
If the torque range is between 5 ft-lb to 150 ft-lb, you should never exceed that. If you try to tighten a fastener with a final torque rating of 165 ft-lb, you will damage the manual wrench. It will also not get the fastener to the right torque, which means your wheel lugs can get loose.
The given accuracy of your torque wrench is only reliable if you use the tool within the recommended range.
Even then, you should not use the torque wrench’s entire given range. The recommended working range for mechanical or analog wrenches is 20 to 100 percent of the given range.
Electronic torque wrenches have a bigger allowance to use the given range, at 10 to 100 percent of the given maximum range.
Try hard to never exceed the given torque range.
Another thing that affects the torque range is the proper usage of the tool. You should never use it to loosen fasteners because that can damage it. Also, never force a drive onto fasteners that are larger than its size.
How torque range affects the accuracy
When people talk about torque wrench range, sometimes, they mean the accuracy range. Manual wrenches are pretty accurate, with many falling in the range of 3 to 5 percent.
Every time you calibrate the torque wrench, you will find that it goes a little off. There is a reason for that. It is because calibrating can raise the accuracy rate to about 2 percent.
d) How to calibrate a manual torque wrench
To enhance the accuracy of your mechanical torque wrench, you have to calibrate at the recommended times, or earlier if you can.
Most manufacturers recommend calibrating torque wrenches at least once every year or every 5000 cycles. However, if you are a frequent user, you should make it two times a year.
You can calibrate the manual wrench on your own and still get a good accuracy rating. However, if you are not sure of your ability to follow precise instructions, take it to a professional.
Here are a few steps to follow to calibrate a mechanical or click type torque wrenches:
What you will need:
- The torque wrench
- Weight – 20 to 35 lb
- Bench vice
- Tape measure
- Paint pen or marker
- Weight rated string or rope
- Paper and pen
Step 1: Measure the torque wrench
Take a place on the handle of the wrench and mark it. Measure the length of the wrench from the middle of the drive where the socket attaches to the place where you made your mark on the handle. Record the measurement (in inches) on a piece of paper.
Step 2: Secure the torque wrench on your bench vise
Secure the wrench on the vise by the drive side (with socket included), and if you don’t have one, use a socket to secure the wrench on a lug nut on the wheel of your vehicle or on any other equipment.
This leaves the handle free. It is important to ensure only the socket with lug nut is secured on the wrench.
Step 3: Calculating
Take the weight that you intend to use and divide it by the length of the wrench (from the socket to the mark you made on the handle).
If you are using the 30 pounds of weight and the length of the wrench to the mark was 15 inches, to get the total inch-pounds torque, multiply 30 by 15. The answer is 450 inch-pounds.
You can divide this by 12 to get the torque in ft-pounds, since 12 inches make up one foot. This is going to be 450÷12 = 37.5 ft-pounds.
4. Check the calibration with your weight
Tie your weight securely with the string, make sure it is rated for more than the weight at hand. Make a noose that can slip easily on the handle of the torque wrench. The weight should not touch the ground.
Set the torque wrench to the value that you arrived at when you did your math. Slip the loop you made to the place where you had made your mark on the handle. The weight stays suspended.
Listen to the torque wrench. If it does not click, it is accurate, so no further action is needed from you.If it clicks, you will need to adjust it as below.
5. Adjust the torque
This will depend on a few things. Mostly, you can increase or reduce the torque by making tension spring tighter.
If the torque accuracy was too far off, you might need to redo your calculations especially if the mark comes on the set screw. If this is where the mark falls, adjust the torque with the weight on the handle.
After recalculating, hang the weight on the mark and test whether the adjustment has worked. If you hear a click, you need to do more adjustment by repeating the process until you hear no click.
e) Manual torque wrench chart
f) Best manual torque wrench
Manual torque wrenches are very common. You can try any of the following:
- EPAuto 1/2-inch Drive Click Torque
Made of chrome vanadium material for durability
Sold calibrated to +/-4% accuracy rate
Sold with 5-inch extension bar, ½ to 3/8-inch drive reducer
Knurled handle makes it anti-slip
Torque range is 10 to 150 ft-lb
- TEKTON 3/8 Inch Drive Click Torque Wrench
The torque range is 10 to 80 ft-lb
Fixed square head
It is a 3/8-inch drive with torque conversion chart
It has a reversible ratchet head to measure torque in clockwise and anticlockwise direction
High quality steel build
+/-4% accuracy rate
- LEXIVON 1/2-Inch Drive Click Torque Wrench
Torque range is 25-250 ft-lb
Calibrated to +/-4% accuracy rate
Chrome vanadium steel construction with electro-black finish
Ratchet head is reversible so it can tighten fasteners in anticlockwise direction too
½-inch drive
- GEARWRENCH Micrometer Torque Wrench 30-250 ft/lbs
½ -inch drive, but even a 3/8-inch drive is available
The torque range is 30 to 250 ft-lb, but there are more varieties
Made of polished alloy steel
Has a higher torque accuracy of +/-4%
Has a knurled anodized aluminum handle for comfortable and anti-slip grip
- CRAFTSMAN Torque Wrench
Available in 3/8-inch drive
Has a locking function to prevent slipping
The torque range is 20 to 100 ft-lb
Scale comes in metric and imperial units
It exceeds ASME (American Society of Mechanical Engineers) specifications for torque wrenches