01 April 2018
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: credit: © Gary Stretton
Tightening fittings to correct values could be the difference between failure and prolonged success, says Gary Stretton
Correctly tightened fittings are critical for reliability and safety, making these the main reasons for using a torque wrench. Ensuring components are correctly fitted needs to be more specific than tightening as far as you can and then a bit more. Equally, components that are under-tightened, such as cylinder heads, will prematurely fail – and without a torque wrench this is easily done. For example, a fitted engine offering resistance to your ratchet turns makes it easier to tighten 90 lb ft cylinder head nuts than a loose engine on a trolley or the floor.
Torque wrenches are available in an array of drive socket sizes, measuring scales and physical size, so matching one or more to your needs depends on intended use. A one-off engine rebuild is a different discipline to regular suspension work for off-road use, for example, or for fitting a variety of wheel types in a professional environment.
All the wrenches tested are ISO 6789 compliant, meaning they are calibrated for accuracy before sale. A certificate issued with the wrench will give the calibration results you can expect at different settings across the torque ranges. This is important because it allows you to fine-tune the wrench to critical settings if necessary. If your wrench use is confined to an annual service or one-off restoration, buy a wrench with the broadest range possible to match the torque values provided in a workshop manual.
What to look for
What to look for
• Measuring scales used vary greatly, but conversion charts are easy to find online if you need to convert available data.
• Overall size. Limited access such as on suspension components can hinder the use of larger wrenches.
• Head size. Larger head sizes can struggle on fittings in tight
spaces.
• ISO 6789 certification. Issued with the tool stating its accuracy and allowing adjustment of values accordingly.
TEST RESULTS
Digital technology meets engineering in this package
CLARKE DIGITAL TORQUE WRENCH
Price: £92
Clarke’s vibrant digital wrench is packed with user-friendly features and wide operating ranges. A few minutes spent reading the instructions is essential to master the features and achieve the correct torque settings. Once set, there is no slipping handle grip or alterations to your preset to worry about. The LCD display can be backlit and audible warnings can be set in increments if desired. The comfortable handle provides plenty of grip and leverage.
KEY FEATURES:
• Four torque ranges: 20-200 Nm, 14.75-147 lb/ft, 177-1770 lb/in, 2.04-20.39 Kgm
• Target torque value preset with audible alarm
• Low battery indicator
• Chrome plated
• Soft grip handle
• Push button socket release
• Calibrated to BS EN ISO 6789
• Accurate to +/- 2%
• Auto power off
• Length 618 mm
• Storage case
Search for: Item PRO237; machinemart.co.uk
Slimline design with push-through head
DRAPER TORQUE WRENCH
Price: £148
Draper’s simple-looking wrench hides its solid abilities. The slimline proportions aided by the ratchet head design allow the head to function in close proximity to other components in situ. In use, the simple but satisfying click function is also visible, making accurate torquing easier to judge. To set and lock the torque setting, simply fold out the rotation bar, rotate the handle to set the torque and fold it back in again. The setting remains locked for peace of mind. Each wrench comes with its own calibration certificate.
Key features:
• Double-sided push-through head
• Soft grip handle
• Micrometer type mechanism adjustment
• Three torque ranges: 40-160 lb/ft, 50-225 Nm and 5-23 Kgm
• Tested and calibrated to DIN-ISO 6789 with individual calibration certificate
• +/- 4% at three points: 20%, 60% and 100% of range (45 Nm, 135 Nm and 225 Nm)
• Storage case
• Length 625 mm
Search for: Item: 83317; drapertools.com
Excellent user-friendly features with this long wrench
PROXXON MICROCLICK TORQUE WRENCH
Price: £165
Proxxon’s MicroClick made rapid, light work of our test from removing it from the box to achieving the torqued value set on our cylinder head. The single range Nm scale is divided into two see-through windows. The main scale sets the closest value in fifths and the second in smaller micro increments. Pull back the end of the ergonomic grip end ring to unlock, set the value and push back the grip end ring to lock securely. The push button release and microclick ratchet work smoothly. Issued with a calibration certificate.
Key features:
• Ratchet mechanism with reversing lever
• Push button socket release
• Ergonomic handle grip
• Single torque range: 50-320 Nm
• Length 610 mm
• Storage case
Search for: Item: MC320; axminster.co.uk
Traditional-style ratchet with extension bar and ˚” adaptor
SILVERLINE TORQUE WRENCH
Price: £32
Silverline’s bargain has its merits for occasional use on items with a degree of tolerance, though it proved awkward to use at the highest torque. The locking mechanism must be very tightly fastened to prevent the grip slipping, altering the torque setting. The ratchet action is a little coarse but the inclusion of the adaptor socket is welcomed. Crucially, no lb ft range and no ISO certificate, so accurate settings can’t be made against individual wrench tolerances.
Key features:
• Chrome vanadium steel
• Reversible ratchet head
• Knurled adjustment handle and locking ring
• EN ISO 6789 and DIN 3121
• Accuracy +/- 4%
• Two scale ranges: 28 to 210 Nm and resolution 1 Nm. Also 2.8 to 21.7 Kgm
• 125 mm extension bar, 1/2” to 3/8” drive adaptor (202 Nm max)
• Overall length 480 mm
• Plastic storage case
Search for: Item: 633567; silverlinetools.co.uk
Traditional micrometer design
SEALEY TORQUE WRENCH
Price: £45
Sealey’s traditional-style wrench offers a decent range of torque settings in the two most popular ranges. The incremental markings have random numbering so calculating the correct setting requires basic arithmetic. The locking screw must be tight to prevent the handle slipping, altering the torque. Ratchet quality is good.
Key features:
• Chrome vanadium steel
• Heat-treated reversible ratchet head
• Knurled adjustment handle and locking ring
• BS EN ISO 6789:2003 certificate, individually tested at three points: 20%, 60% and 100% of range
• Two scale ranges: 27.1 to 203.5 Nm. Also 20 to 150 lb/ft
• Overall length 465 mm
• Plastic storage case
Search for: Item AK624; sealey.co.uk
6 top tips for looking after your wrench
1. Never undo fittings using a calibrated torque wrench.
2. Reset any torque wrench to its rest torque position when not in use.
3. Ideally, recalibrate a wrench annually if it’s in regular use.
4. Never use a wrench beyond its stated torque range.
5. Never lend a torque wrench to a friend who doesn’t know how to use it.
6. Never forget No.5.
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