Assembly Planbook - April 2008 - (Page 50) Fastening Matching Tool Types With Fastening Tolerances ESTIMATED TORQUE TOLERANCE Tool Type Torque wrench Adjustable shut-off nutrunner Cordless impact tool with control Transducerized pulse tool Shut-off pulse tool Stall pulse tool Single, Medium Joint Class 1, ±10% Class 1A, ±15% Class 1, ±10% Class 1, ±10% Class 2, ±20% Class 3, ±30% Combined Joints Class 1, ±10% Class 2, ±20% Class 3, ±30% Class 3, ±30% Class 3, ±30% Class 3, ±30% The torque capability displayed by most of the tools in this study is sufficiently accurate to meet the torque tolerances of all three tolerance classes. This is particularly true if the tool is used on just one joint. However, if the tools are used without adjustment on different joints, the picture changes substantially. and Class 3. These classes cover all but the most highly stressed bolts, such as connecting rods. The torque capability of most of the tools in our study is sufficiently accurate to meet the tolerances of all three classes. This is particularly true if the tool is used on just one joint. In many production applications, this is not a problem. Tools are set for a particular assembly and torque value, and are then used only for that application. Under these circumstances, pulse tools perform with comparable accuracy to the shut-off nutrunner and other geared clutch tools. However, if the tools are used without adjustment on different joints, the picture changes substantially. The combined joint variability of the pulse and impact tools increases to the point that they will meet the requirements only for a lower class of fastening. It is clear that the superior performance of the manual wrench and the adjustable clutch nutrunner arises from their ability to work accurately on different joints. However, it is also clear that the pulse and controlled impact tools can produce acceptable torque accuracy, even on different joints, provided the tightening tolerances are less stringent. Engineers can often account for that when designing the joint and specifying the fastener. For more information on tool testing, joint design and other fastening issues, call Impact Fastening at 215-345-4470. A 50 ASSEMBLY / April 2008 www.assemblymag.com ASB04084global.indd 1 3/10/08 2:32:14 PM http://www.globalautomation.com http://www.globalautomation.com http://www.assemblymag.com
For optimal viewing of this digital publication, please enable JavaScript and then refresh the page. If you would like to try to load the digital publication without using Flash Player detection, please click here.