Gedore Newsletter - Changing wheels - safe distribution of forces
The weather is telling us – soon it will be time to change from summer to winter tyres. For the controlled tightening of wheel nuts a torque wrench should be used, regardless of whether the change is carried out by a private person or a specialist in a workshop.
The torque wrench in general is a hand-operated tool for carrying out controlled screw connection work. A controlled screw connection is when the force used for screwing is exactly specified and adhered to. Torque wrenches have a scale for this and use a tactile, visual or acoustic signal to indicate when the desired torque has been reached. With the mechanical torque wrench GEDORE DREMASTER®, which is produced in Germany, the signal is triggered automatically and noticeably felt and heard by the user. This wrench also has a dual scale with main and alternative unit, so you can measure both in newton metres (N•m) and in foot pounds (ft•lb). Both the setting of an incorrect unit and reading errors can be avoided by simple selection using the change-over switch. "Loading beyond the signal can damage both the screw connection and the torque wrench,” says Heiko Blase, the responsible product manager at GEDORE. A torque wrench with a mushroom head and push-button release also prevents accidental pulling out of the whole square drive when changing the sockets.
Use the right nuts
When changing the wheels, make sure the correct wheel nuts are used for the rim in question. The demands on a wheel nut for steel rims are different to those on one for aluminium rims. Because steel rims are harder than aluminium rims, if the wrong nut is used no optimal grip can be achieved. Wheel nuts can loosen themselves or even break.
Tighten the wheel nuts properly
The tightening sequence of the wheel nuts also plays an important role in avoiding distortion of the rim. Therefore, the nuts are always tightened crosswise, so that over the entire contact surface a uniform preload is built up.
Use the specified tightening values
In general, any private person with an appropriate mechanical torque wrench can safely perform a wheel change. He reads the required torque values for his vehicle from the vehicle’s manual or from relevant tables, and sets them on the torque wrench. The set value is reached by slowly and evenly tightening until the wrench issues a tactile impulse and audible signal. To protect the mainspring of the mechanical torque wrench, after each use the torque wrench should be reset to the lowest value.
In areas where a quality management system requires that measurement results are recorded in writing, mechanical wrenches are no longer enough. For safe torque tightening with documentation an electronic torque wrench is appropriate, it shows the exact tightening value of the screw connection. There is also a documentation of actually tightened values, which allows checking that all nuts or bolts have been properly tightened.
Users can find relevant details of the correct tightening values in the vehicle manual.
Regular checking of torque wrenches
All torque wrenches meet the requirements of DIN EN ISO 6789 within a certain tolerance range, i.e. the set torque values may be exceeded or undershot by a specified percentage. Once calibrated a torque wrench must be checked regularly to ensure its accuracy. DIN EN ISO 6789:2003 recommends annual calibration or after 5000 load cycles. Where tools are used more intensively or screwed connections with safety relevance are involved, inspection intervals of 3 to 6 months are recommended. During calibration, target and actual values are compared. If significant deviations within the required tolerance are detected, the wrench must be readjusted. The adjustment is carried out with the help of an electronic torque tester, a special adjustment tool, and expertise.
Calibration should be performed by authorised specialist personnel, an accredited DAkkS calibration laboratory (formerly DKD calibration) or by the manufacturer themselves. Depending on requirements, such maintenance can involve DAkkS calibration or factory calibration traceable to national standards.
In order to gain absolute clarity on the tolerance of your own torque wrench if necessary, purchasing your own tester is recommended. For this there is simple test equipment designed for the range 0.2 to 3150 N•m, so-called "plug and work" devices with an integrated transducer that guarantee an accuracy of plus/minus one per cent when checking or setting clockwise torque wrenches.
AKOH Team
The torque wrench in general is a hand-operated tool for carrying out controlled screw connection work. A controlled screw connection is when the force used for screwing is exactly specified and adhered to. Torque wrenches have a scale for this and use a tactile, visual or acoustic signal to indicate when the desired torque has been reached. With the mechanical torque wrench GEDORE DREMASTER®, which is produced in Germany, the signal is triggered automatically and noticeably felt and heard by the user. This wrench also has a dual scale with main and alternative unit, so you can measure both in newton metres (N•m) and in foot pounds (ft•lb). Both the setting of an incorrect unit and reading errors can be avoided by simple selection using the change-over switch. "Loading beyond the signal can damage both the screw connection and the torque wrench,” says Heiko Blase, the responsible product manager at GEDORE. A torque wrench with a mushroom head and push-button release also prevents accidental pulling out of the whole square drive when changing the sockets.
Use the right nuts
When changing the wheels, make sure the correct wheel nuts are used for the rim in question. The demands on a wheel nut for steel rims are different to those on one for aluminium rims. Because steel rims are harder than aluminium rims, if the wrong nut is used no optimal grip can be achieved. Wheel nuts can loosen themselves or even break.
Tighten the wheel nuts properly
The tightening sequence of the wheel nuts also plays an important role in avoiding distortion of the rim. Therefore, the nuts are always tightened crosswise, so that over the entire contact surface a uniform preload is built up.
Use the specified tightening values
In general, any private person with an appropriate mechanical torque wrench can safely perform a wheel change. He reads the required torque values for his vehicle from the vehicle’s manual or from relevant tables, and sets them on the torque wrench. The set value is reached by slowly and evenly tightening until the wrench issues a tactile impulse and audible signal. To protect the mainspring of the mechanical torque wrench, after each use the torque wrench should be reset to the lowest value.
In areas where a quality management system requires that measurement results are recorded in writing, mechanical wrenches are no longer enough. For safe torque tightening with documentation an electronic torque wrench is appropriate, it shows the exact tightening value of the screw connection. There is also a documentation of actually tightened values, which allows checking that all nuts or bolts have been properly tightened.
Users can find relevant details of the correct tightening values in the vehicle manual.
Regular checking of torque wrenches
All torque wrenches meet the requirements of DIN EN ISO 6789 within a certain tolerance range, i.e. the set torque values may be exceeded or undershot by a specified percentage. Once calibrated a torque wrench must be checked regularly to ensure its accuracy. DIN EN ISO 6789:2003 recommends annual calibration or after 5000 load cycles. Where tools are used more intensively or screwed connections with safety relevance are involved, inspection intervals of 3 to 6 months are recommended. During calibration, target and actual values are compared. If significant deviations within the required tolerance are detected, the wrench must be readjusted. The adjustment is carried out with the help of an electronic torque tester, a special adjustment tool, and expertise.
Calibration should be performed by authorised specialist personnel, an accredited DAkkS calibration laboratory (formerly DKD calibration) or by the manufacturer themselves. Depending on requirements, such maintenance can involve DAkkS calibration or factory calibration traceable to national standards.
In order to gain absolute clarity on the tolerance of your own torque wrench if necessary, purchasing your own tester is recommended. For this there is simple test equipment designed for the range 0.2 to 3150 N•m, so-called "plug and work" devices with an integrated transducer that guarantee an accuracy of plus/minus one per cent when checking or setting clockwise torque wrenches.
AKOH Team
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