How to Set a Torque Wrench Accurately

Setting a click-type torque wrench comes down to three things: unlock the handle, spin the grip until the main scale and the micrometer collar together add up to your target figure, then lock it again before you touch a single fastener. Get the two scales mixed up and you can be 20 or 30 Nm out without realising, which is the difference between a wheel nut that holds and one that does not. Here is how to read the scales properly and set the tool with confidence.

Know which type you are holding

Most home and garage wrenches are click type, sometimes called micrometer adjustable. You dial in a figure and the wrench clicks audibly when the fastener reaches that load. Beam wrenches have no setting at all, you just watch a pointer as you pull, and digital wrenches let you key the figure into a display. This guide covers the click type, because that is where the setting mistakes happen.

Find out what torque you actually need first

Setting the wrench is easy. Knowing what to set it to is the part people skip. Never guess a figure from feel or from what a similar bolt took last time. Sources worth trusting, in order:

• The vehicle handbook or workshop manual for that exact model and year
• The manufacturer instructions supplied with the part you are fitting
• A published torque chart for the bolt grade and thread size, used only when nothing model specific exists

Write the number down before you pick the wrench up, and note the units. Nm and lb-ft are not interchangeable, and roughly 1.36 Nm equals 1 lb-ft. Alloy wheel nuts on a typical family car sit somewhere around 110 to 120 Nm, but that is an illustration, not a substitute for looking yours up.

Setting a click-type wrench step by step

1. Unlock the handle. Depending on the design, you either pull the knurled locking ring down at the base of the grip, or turn a small locking knob at the very end of the handle anticlockwise. Nothing should be forced. If the grip will not turn, the lock is still engaged.
2. Read the main scale. This is the long scale printed up the shaft, usually marked in steps of 10 Nm. The figure you want is the one at or just below your target.
3. Read the micrometer collar. This is the rotating band on the handle, marked 0 through to 9 or similar. It adds the remainder to the main scale figure.
4. Add the two together. For 115 Nm, wind the handle until the main scale line sits at 110 and the collar reads 5, with that collar mark lined up against the vertical reference line on the shaft. Some wrenches use a window rather than a line, so the correct number simply appears in the window.
5. Approach from below. Wind up to your figure rather than overshooting and backing down. Coming down onto the setting can leave slack in the mechanism.
6. Lock it. Push the ring back up or turn the end knob clockwise until firm. Give the grip a gentle nudge to check it will not creep while you work.

Using it once it is set

Run the fastener down by hand or with a plain ratchet first. A torque wrench is a measuring instrument, not a driver, and using it to spin nuts down from scratch wears the mechanism for no reason. Once the fastener is snug, fit the wrench and pull smoothly with one hand on the centre of the grip. Where you hold it matters more than people expect, because gripping right at the end of the handle changes the effective leverage on some designs.

Pull steadily over a couple of seconds rather than jerking. When the wrench clicks, stop immediately. There is no second click and no reward for pulling through it, and continuing past the click simply overtightens the fastener while telling you nothing. If you are unsure whether you felt it, back the fastener off slightly and repeat rather than pulling harder.

Sequence and multiple passes

Anything with several fasteners around a joint, wheels, cylinder heads, manifolds, wants a star or criss cross pattern rather than working around in a circle. On higher torque jobs it is common practice to make two or three passes, at half torque then three quarters then the final figure, so the joint pulls down evenly.

What to do when you have finished

Wind the setting back down to the low end of the scale before it goes back in the case. On most click wrenches that means the lowest marked figure, not zero, since running the spring completely slack can be as bad as leaving it loaded. Leaving a wrench stored at 200 Nm keeps the internal spring compressed for months and the calibration drifts. Store it in its case, keep it dry, and treat dropping it on a concrete floor as a reason to have it checked rather than shrugged off.

Calibration is not permanent either. Typical guidance is a check every 12 months or around 5,000 cycles. If the wrench has taken a knock or the click has started to feel vague, act on it before you trust it with brakes or suspension.

Common mistakes worth avoiding

• Adding the collar figure to the wrong main scale mark, so 110 plus 5 becomes 120 plus 5
• Setting in Nm when the spec was in lb-ft, or the reverse
• Using an extension bar on the handle, which throws the reading out entirely
• Using a click wrench to loosen fasteners, which can damage the mechanism
• Forgetting to lock the handle, so the setting creeps as you work
• Torquing over a dirty or damaged thread, which absorbs load and gives a false reading