Buying guide for best torque wrenches
Over-tightening nuts and bolts is a constant problem for DIYers and professional mechanics alike, on everything from the cylinder head of a semi, to the gear train of a racing cycle.
The solution is a torque wrench. A precision instrument designed for one job: making sure your nuts and bolts are done up with exactly the right amount of force.
The challenge is identifying the torque wrench that’ll best meet your needs.
If you're an engineer or mechanic you might have job-specific requirements. If you're not a pro, but like to work on your own vehicles, you'll probably want a good all-around wrench.
BestReviews is here to help you choose.
Types of torque wrench
Many people will be familiar with what we think of as a "standard" torque wrench – those that look much like a ratchet-drive socket wrench. There are a couple of others:
Preset torque wrenches: Also called torque drivers. Often small, gripped in the palm of the hand. They are set for a single torque amount. Popular with cyclists because of their light weight and portability.
Deflecting beam torque wrench: Available in a wide variety of ranges, from light engineering to heavy industrial. A long beam runs from the head where the socket is attached, down to a scale by the grip. The deflection of this beam, left or right, indicates the amount of torque. It's a common and popular tool in many industries, but the socket is fixed. There's no ratchet action, so it can be difficult to use without plenty of space.
The ones most of us recognize are known as micrometer torque wrenches, though there are some differences.
Along with the different types of torque wrench, there are also different drive sizes. A 1/2" drive is common among tools designed for automotive use. Also commonly available are 1/4", 3/8" and 3/4" drives.
Expert Tip
After use, always return your torque wrench to zero, or the lowest permitted level. Leaving it “dialed up” can put unnecessary tension on components.
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Click wrenches
The most common type available. An audible click, which can also be felt by the operator through the grip, warns when the required torque is reached.
Great combination of performance, durability, ease of use and value. Accurate when used properly.
If pressure is applied too rapidly, they can over-tighten. Steady pressure is recommended, stopping immediately the first click is heard. It's common for users to think they need to release and apply an extra click "just to make sure." This is incorrect.
Break-over wrenches
Very similar to click wrenches, but with a hinged section – usually near the socket head – that “breaks” when the required torque is reached.
Easy to use. Good durability and value. Accurate when used properly.
Continued pressure after break will over-tighten. Some people find the 'break' action unpleasant.
Cam-over wrenches
Similar in appearance to click wrenches. Have a built-in slip mechanism that releases pressure when the set torque is reached.
Easy to use. Will not over-tighten, even with renewed pressure. Guarantees repeatable accuracy that is unaffected by user skill-level.
Complex mechanism makes them very expensive.
Dial wrenches
At first glance, looks like a click wrench with an analog dial, but the dial is there as a guide only, and does not set torque limits.
Durable. Can be very accurate.
Bulky. Difficult to use. The problem with dial wrenches is that they rely on a high level of operator skill. Most have no audible warning, nor do they break or cam-over. You must watch the dial (not always easy), and react accordingly.
Digital wrenches
These are the most recent development, and are becoming quite common. An LCD readout displays torque readings. "Traffic light" LEDs and/or audible warnings change as the desired torque level is approached.
Can be accurate to four decimal places. They’ve become competitively priced. Some can store data for later comparison and record keeping.
No mechanical limit, so again, they rely on user skill. Some concerns over robustness of electronic components. Negligible advantages over mechanical alternatives.
Did you know?
When using a “click” type torque wrench, one click is all you need to tell you you've reached the desired limit. Once you've heard that click, move on to the next fixing. You'll save yourself time and effort.
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Torque measurements
Torque is usually measured in the imperial scale of foot pounds (ft. lbs.), or the metric scale of Newton meters (Nm). Though less common, it can also be measured in inch pounds (in. lbs.) or kilograms per centimeter (kg. cm.).
A mechanical torque wrench will have one or two of these scales (generally foot pounds and/or Newton meters).
Digital models can often be set for all of them, but not always. Don't assume so.
For your safety
Don't use an extension bar on a torque wrench – the majority are calibrated to work with the handle length as supplied.
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Torque wrench range and accuracy
The most popular torque wrench is the click-type, or its digital counterpart, so those are what we have focused on with our recommendations. However, the following rules and characteristics can be applied to any kind of torque wrench.
The accuracy of a torque wrench should be stated as either:
Full Scale (FS), or
Indicated Value (IV).
This can be a little confusing.
A torque wrench that quotes, for example, +/- 4% over the Full Scale, may be less accurate than that at certain points along the scale (commonly lower torque settings). Its overall average accuracy is +/- 4%.
A tool that quotes +/- 4% at any Indicated Value is never more than 4% imprecise, anywhere on its scale. It is more accurate than one that quotes Full Scale.
This distinction isn't always made clear by manufacturers. Whether this is important to you will depend on the precision your job requires. If it's a concern, check with the manufacturer before purchase.
The other important point is that with click-type torque wrenches, accuracy is not quoted over the whole range. 20% to 100% is common. This is because it's difficult for this kind of mechanism to maintain control, and therefore accuracy, at the lower end.
So if, for example, you have a wrench with a range from 25 to 250 foot pounds, it may not achieve its stated accuracy until it gets to 45 foot pounds (20% of range). If you need accuracy at a lower setting, it may be necessary to choose a smaller overall range. A wrench with a range from 10 to 150 foot pounds, should work accurately from 28 foot pounds on up.
Alternatively, dial-type torque wrenches can maintain accuracy from 0% to 100%. However, they are considerably more expensive.
Expert Tip
When setting a manual torque wrench, always start from zero – or the lowest setting – and work up. You'll get a more accurate setting than coming down the scale.
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Torque wrench features
The popular click-type mechanical torque wrench is easy to use, but settings can slip. A locking collar (sometimes called a slip lock) prevents this from happening.
If you're working with high torque settings, a longer handle will enable you to apply pressure more evenly, and so maintain better control. A ratchet head usually allows you to use a larger tool without working space becoming an issue.
Plastic and rubber grips increase comfort, so you're less likely to drop your torque wrench – particularly on cold days.
Some digital models automatically shut down if left unattended, saving battery life. Some have charge indicators. As with all electronic devices, it's an area that changes rapidly, and manufacturers like to add bells and whistles to attract you. Ask yourself whether these things are worth the extra cost, or just gimmicks.
"It is possible to use some torque wrenches for loosening, but we don’t recommend it. You can easily exceed the maximum torque, and do permanent damage."
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What does a good torque wrench cost?
The enormous range of types and sizes of torque wrench makes it difficult to apply general rules when it comes to pricing.
You can get a perfectly good torque wrench for a bicycle for $25. You can get an entry level model for home auto repair at around $40, but a professional mechanic or an engineer requiring more precision might easily spend five times that amount.
Our buying guide should help you narrow down your requirements. Armed with this information, you can compare individual elements until you arrive at the best torque wrench for your particular needs.
Caution
Never use a torque wrench as a breaker bar.
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Torque wrench tips
If you're working on a complicated job, and you're worried about losing track of where things go as you take them apart, use your cell phone to snap "before" and "during" pics. Then you've got handy reference – in the correct order – when it comes time to put everything back together.
Unless specifically instructed by a manufacturer, never grease or oil nuts and bolts before tightening. You may think lubrication will make them easier to undo next time, but it can stop them tightening properly. If the maker didn't do it, you shouldn't either.
Tighten in three stages. First, wind on the nuts or bolts by hand. They don't have to be tight, you're just getting them on there.
Second, set the torque wrench to half the recommended total. If you have more than one nut or bolt, there's probably a set sequence recommended by the manufacturer. It's important to follow it.
Third, set your wrench to the final torque amount, and follow the sequence again. This ensures even, accurate tightening – particularly important on something like a cylinder head.
FAQ
Q. Do torque wrenches need specific care or maintenance?
A. A high-quality torque wrench is a durable tool that should give many years of service, but they need some looking after. It varies depending on type, so always follow manufacturer's instructions carefully. Most is common sense. Take care not to drop it when in use. Keep it clean. Store in a separate case so other tools can't damage it. Torque wrenches should be recalibrated periodically – once a year is recommended for a regularly used tool. Again, follow maker's advice.
Q. Do I really need to use a torque wrench on lug nuts? In the auto shop, they just use an air gun?
A. When manually tightening lug nuts, it's surprisingly easy to over do it. It's possible to strip or break wheel studs, and even warp brake rotors. Both are expensive to fix, and the latter has the potential to be extremely dangerous. Use of a torque wrench helps avoid such problems.
While they certainly do use air tools in pro shops, and there's nothing like an impact wrench for breaking a stubborn nut free, the tool has a built-in clutch that's used when replacing your wheel, to avoid over-tightening.
Q. How do I convert foot pounds (ft. lbs.) to Newton meters (Nm) and vice versa?
A. 1 foot pound equals 1.3558 Newton meter, so if you want to turn that around, 1 Newton meter equals 0.7376 foot pounds.
You can do the math from there. Alternatively – and much more easily – you can either look up conversions on the internet (you can print out a chart and tape it to the garage wall), or get a conversion app for your smartphone!
