You can tighten nuts and bolts with many tools, but to get it exactly right, you need a torque wrench. Here’s our comprehensive guide to bring you up to speed.
A torque wrench is, in essence, the ultimate version of the common ratcheting socket wrench. These things function in exactly the same way as a normal ratcheting socket wrench, are available in the usual common ¼” 3/8” and ½” socket fitments, but have the added benefit of being able to tell you exactly how tight you have fastened a nut or bolt. As they cost more, are bulkier, and are generally more fragile than a conventional ratcheting socket wrench, people only tend to use them when the user truly requires them. But when that time comes, they are a vital tool.
Why do I need one?
While almost every fastener on a car has an official factory torque setting, i.e. how tight they should be, it’s fair to say the vast majority of them you can do by a mix of feel and experience without issue, allowing you to use a conventional ratcheting socket wrench to do the work. Unfortunately this brings up issues in various circumstances, and then you need a torque wrench.
Firstly, the aforementioned experience. It’s not uncommon for less experienced people to fasten nuts and bolts too little or too much, and for obvious reasons either of these can potentially lead to disaster. I’m sure all of us has snapped a bolt at least once in our lives!
Secondly, if you truly want to do everything exactly by the book, maybe it’s a very high value car or you’re just a perfectionist, you can use one to do every single fastener to the factory listed torque specs if you wish.
Lastly, most commonly, and most importantly, certain fasteners on a car, especially ones relating to internal engine parts, really do need the correct torque setting to maintain exact clearances and strengths. Trying to do certain parts by feel alone would be hugely risky at best, but more than likely absolutely disastrous.
Mechanical Torque Wrenches
Mechanical torque wrenches are the most common type on the market and the ones people are most familiar with. However, it might surprise you to know that there’s a few variations of the mechanical torque wrench on the market.
Clicking Torque Wrench
Firstly, and by far the most common one you will see for general automotive use, is the clicking torque wrench. You set your desired torque via the adjuster at the end, and then tighten the nut or bolt until you hear and feel a click. That click indicates you’re at your set torque – job done! There’s nothing to stop you tightening it even further, and people who don’t understand what the click means often keep going until something snaps, but as long as you know, it’s an accurate and easy item to use.
Want one of your own? Consider this EPAuto option ($38.87 / £48.01) and check out price comparisons below.
Slipper Torque Wrench
While in theory the best and most fool proof design, a slipper torque wrench takes any potential mistakes out the equation because, as the name suggests, once you hit the specified torque the wrench slips, making it impossible to over-tighten the fastener. Unfortunately that’s where the good news ends, as slipping torque wrenches are either set to a specified torque from the factory, or are only adjustable if you’ve got access to specialist equipment. Due to this, you only really find slipping torque wrenches on factory production lines where workers need the same torque figure over and over.
Beam Torque Wrench
Lastly, the beam torque wrench. These work by having a pointer which indicates the correct torque number as the main beam is slightly bent as you tighten the faster. These are often popular as there’s no need to adjust the wrench for each torque setting, and generally are a little more accurate than a clicking one too. Unfortunately they tend to be longer and bulkier than clicking wrenches, don’t have a ratcheting mechanism, and with no audible indication that you’re at the correct torque figure they’re easier for a less observant person to over-tighten a fastener.
Electrical Torque Wrench
Probably the best overall design, an electronic torque wrench is a manually operated ratcheting wrench, like a conventional clicking torque wrench, just with some added modern technology. Internally they work like a strain gauge, connected to a small electronic display which allows you to set the torque at the push of a button. That display also allows you to do things like read the current torque figure, and sound an alarm when you’ve reached your specified number. Most pros would agree that these are the most accurate and easy to use wrenches, and the alarm makes them more fool proof than the clicking ones.
Some electronic wrenches also have an angle meter too, which can tell you how many degrees you have turned the wrench. This is handy as some fasteners, especially things like head bolts, have both a torque and angle setting. For example, you might need to torque them up to 100lb/ft, then turn it another 90 degrees. On a conventional clicking wrench you need to do that part manually, but some electronic products take any potential inaccuracy out of the equation.
You can check out some cordless options here.
Left and Right Handed Torque Wrenches
While the vast majority of fasteners are right hand thread, there are a few specialist threads. For example, many turbocharger compressor wheel nuts feature a left hand thread design. While all torque wrenches are reversible like any other ratcheting socket wrench, make sure the one you are using actually measures torque when going the opposite way, as most do not!
Assuming yours does and only realizing when you’ve completely snapped the shaft of a turbocharger or similar is an all too common issue on things with a left hand thread, so be aware.
Yes, you can actually get torque screwdrivers too. Of course these are only for light torque applications on small fasteners, but they do exist and are vital for some very intricate jobs. We’re sure you’ve all experienced screws and other small fasteners which simply refuse to undo, or have torn threads making them impossible to tighten. That’s usually because they’ve been over-torqued…
There are many cheap options on the market, but if you want a top-end tool, it might be worth paying a bit extra for something like this precision set from Capri Tools ($134.99 / £167.85). Check price comparisons below: