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Jack Thompson
Jack Thompson

Calibrating Torque Wrenchs How To

But there is more to understanding whether your torque readings are accurate. The torque wrench only measures how much rotational force it takes to turn the fastener, not the clamping load itself. So the torque wrench will only achieve the clamping load you expect if you are turning a fastener under the conditions that the manufacturer assumed when setting the torque specification. In general, the amount of friction depends on multiple factors including surface coatings, temperature, materials, and fastener shape and size. If those factors vary unexpectedly, you may get unintended results that are outside the calibrated accuracy range of the torque wrench.

calibrating torque wrenchs how to

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1. Look carefully. You have to set the torque wrench with your own eyes. If you accidentally set the dial at 98 or 102 when you mean to set it at 100, you have introduced extra error. This can happen if you are looking at the scale at an angle.

2. Turn the torque wrench slowly and steadily, stopping when you hear or feel the click, which indicates that the desired torque setting has been reached. Turning the fastener past the click means you have applied extra, unintended clamping load. Swinging the torque wrench rapidly means you might swing right past the click.

4. Push only on the handle, without applying force anywhere else on the wrench body. The torque wrench measures force at the pivot point just below its head. It has been calibrated so that this force accurately corresponds to the amount of torque shown on its scale only when you apply force on the handle and nowhere else. Most Tekton torque wrenches have a line or groove in the handle to indicate where you should push on the tool. If a line or groove is not present, use the center of the handle.

Our team of calibration technicians are able to assess an array of torque instruments and make adjustments as necessary to ensure that tools remain compliant with their defined standards, ranges and accuracies.

These two calibration standards have been devised by the International Organisation for Standardisation (ISO) specifically for Type I (indicating) and Type II (setting) torque tools. Each standard details the requirements and procedures necessary to maintaining conformance with various Type I and Type II torque tool specifications. Please see below for an overview of each standard.

The ISO 6789-1:2017 standard can be used to determine a declaration of conformance. It details the conformance tests, marking requirements and minimum requirements needed for a Type I (indicating) or Type II (setting) hand torque tool to achieve a declaration of conformance.

This standard pertains specifically to hand torque tools classified as indicating (Type I) and setting (Type II) torque instruments such as those used for the controlled tightening of screws and nuts.

This standard can be used during static (step-by-step) and quasi-static (continuous) calibrations. In these instances, the torque of the instrument-under-calibration is defined by measuring the elastic form change of a deformable body, or is determined using a measured variable which is in proportion to the torque.

As a national company, PASS Ltd is able to calibrate torque equipment in our lab or at your premises. Please contact our calibration team to discuss which of the three options listed below would best suit your requirements:

Abutment screw loosening is still the most common complication reported with implant-supported crowns. One factor that contributes to screw loosening is not achieving the proper torque during the tightening process. Torque application and measurement is usually achieved by using one of the available types of mechanical torque wrench. Of these, the toggle wrench has been shown to produce erroneous readings, and regular testing is recommended. If it is inaccurate, it must be recalibrated or replaced. Calibration typically requires specialized instruments unavailable to most clinicians, so the device must be sent away. This article describes a straightforward, in-office, and inexpensive alternative for testing and recalibrating a toggle torque wrench.

Torquewrench calibration is an important topic to discuss because torque wrenches arean essential tool for anyone involved in mechanical work dealing with bolts andscrews. Whether you are a workshop owner or a DIYer, torque wrenches are usedfor a wide variety of applications from dismantling and assembling of enginesand suspension components to tightening lug nuts of your car.

Inthe industry, torque wrenches have applications much greater in scope andvariety than automotive works as disassembly and re-assembly of heavy-dutymachines requires tightening each fastener at the torque specified by themanufacturer. In order to ensure safety and integrity of mechanical equipmentyou are working with, it is necessary that you get your torque wrench calibratedperiodically.

Torquewrench calibration is required because torque wrenches have the tendency tolose their accuracy over time as the internal mechanism of a torque wrench ismechanical in nature that requires adjustment after certain period of use. Anuncalibrated torque wrench is not trustworthy because you never know the torqueat which it is tightening the fastener and that completely kills the intendedpurpose of using a torque wrench which is to make sure no overtightening orunder-tightening is taking place.

ISO6789-2 (Requirements for calibration and determination of measurementuncertainty in hand torque tools) defines the requirements for calibration oftorque wrenches as well as other torque measuring tools. As per the standard,torque wrenches must carry a "Traceable Calibration Certificate" thatrefers to a piece of document bearing information of torque wrench calibrationdetails including the facility from where it was calibrated, the date ofcalibration and range of error.

1.The required maximum permissible error based on the type of application youare using the torque wrench for. For example, an error of +/-4% is acceptablein majority of applications, however, for research projects in precisionengineering, you may need a torque wrench with +/-2% error otherwise it mayaffect the results of your research.

2.Frequency of useis another factor that determines how frequently you need to calibrate yourtorque wrench. For example, if your torque wrench is being used in a automobileworkshop tightening a hundred fasteners each day, it is likely that it willlose its accuracy earlier than a torque wrench used for occasional DIYapplications.

3.Typical load during torque wrench operation is another factor determining thefrequency of calibration. A general rule of thumb often followed by techniciansand workshops is not to use the torque wrench for more than 80% of its maximumtorque value i.e. if the maximum torque limit on your torque wrench is 100 N.m,it is advisable not to use it for torqueing bolts and screws requiring a torqueof more than 80 N.m. If you are using the torque wrench more often near itspeak value, it may require calibration earlier than if you were using it in say50% of its range.

4.Ambient conditionsduring operation can also have an effect on torque wrench calibrationfrequency. That is so because of the effect of temperature on metallurgy ofmaterials making up components of the torque wrench. Since metals expand inheat and contract at lower temperatures, it affects the accuracy of torquewrench in different seasons, however, for most practical applications, the lossof accurcy is likely to be negligible. Such a problem is more noticeable forprecision engineering applications.

5.Storage conditionscan also affect the accuracy of torque wrenches. For example, it is advisableto dial down your micrometer click type torque wrench to its minimum value instorage as it relieves spring tension and preserves accuracy.

ISO6789-2 refers to a "Control Procedure" that, in simple terms,refers to documenting record of your torque wrench to track its use. It can bein the form of a logbook that records the daily usage of torque wrenches aswell as recording any misuse, mishandling or accident with the torque wrench.Such a documented record will enable you or your workshop to remain confidentof the accuracy of the torque wrench and ascertain the frequency of calibrationbest suited to your applications.

However,in case such a "Control Procedure" is not in effect, that isgenerally the case with majority of the torque wrenches used in workshops andDIY, ISO 6789-2 recommends calibration every 12 months or 5,000 cycles,whichever occurs first. In the light of this point, you should get yourtorque wrench calibrated at least once a year.

Alternatively,you may record the number of times you use your torque wrench in a day or aweek (or any period of choice) and extrapolate it to estimate the number ofweeks or months in which your torque wrenches reaches 5,000 cycles. It willgive you a good idea of whether you need to get your torque wrench calibratemore than once a year or not.

Theabove factors determine periodic calibration frequency of torque wrenches,however, there can be certain occurrences that necessitate calibrationseparately from the periodic calibration. Such factors include,

1.Overload:If you have subjected your torque wrench to an overload, it will requirecalibration. For example, you have a torque wrench with maximum range of 100N.m. You mistakenly kept apllying pressure on the torque wrench even after itclicked at 100 N.m. Under such an occurrence, it is necessary that you get yourtorque wrench calibrated again. ISO 6789-2 specifies that calibration isrequired if an overload of 125% is applied i.e. while the maximum value oftorque wrench is 100 N.m, you used it for 125 N.m.

2.Repair:If you have got your torque wrench repaired, it will need calibrationimmediately. That is so because repair requires disassembly of torque wrench inmost of the cases that disturbs the internal adjustments made in lastcalibration resulting in loss of accuracy.


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