An Impact Driver has evolved into a compact cordless battery powered portable hand tool that has made its way unto numerous metal building erection jobsites with negative consequences. An Impact Driver is now a powerful battery powered hand tool that delivers a strong, sudden rotational and downward force which previously has been a mechanics tool of choice to loosen larger screws and nuts that are corrosively “frozen” or locked bolts due over torque pressure originally applied during their original install. Other trades have now experienced the advantages of the use of both the rotation and concussive blows of these beasts to power drive screws thorough the thickest densest woods, concrete and steel when called upon. The result of the combination of the rotation and concussive blows of the Impact Driver is raw unadulterated power that delivers two to three times more turning force (torque) than average cordless battery powered Drill/Driver screw guns.
The use of Impact Driver equipment resulted in the Metal Construction Association (MCA) addressing the situation in their Technical Bulletin dated 8/28/2013 Version 1 “Proper Tools for Fastening Metal Panels”. The Impact Driver is specifically addressed “Tools Not Recommended: Impact Drivers are not recommended for fastening metal panels, or composite panels used for roof and/or wall system installation. These tools can cause damage to the drill points, break screws, chip painted surfaces, and strip threads on Type 300 stainless steel screws. Overdriven screws also damage the EDPM sealing washer and could potentially cause leaks.” The exact same statement was echoed by the National Frame Building Association (NAFB) Technical Bulletin “Proper Tools for Fastening Metal Panels” Version 1 in 2014. The conclusion of the MCA technical bulletin states that “Use of the wrong tool or a driver with excessive RPM can lead to fastener damage and problems. Among these are damage to fastener heads, over-driving, scratched and damage to paint finishes leading to premature corrosion.” In a Canadian Sheet Steel Building Institute (CSSBI) article release CSSBI Sheet Steel Facts 42 March 2015 “Fastening Prepainted Sheet Steel Roofing and Siding” states “No matter the evaluation criteria, the impact driver was significantly the worst performer. The impact forces acting on the head will damage the screw surface and lead to early corrosion. While the test were done on painted screw heads. The same conditions would apply to unpainted and nylon head screws as well.” Numerous screw manufacturers including Seal Tite Fastening Systemshave weighed in on the non recommended usage of impact drivers with warning posters such as the one attached boldly noting “ IF YOU CARE ABOUT THE QUALITY OF YOUR BUILDING YOU WILL NOT ALLOW THE USE OF IMPACT DRIVERS FOR FASTENER INSTALLATION!”.
Main Ingredients for a Proper Install
All entities previously noted agreed there are three main ingredients pivotal for installing metal panels for an aesthetically, leak free and proper performing roof or wall systems. The first ingredient is the proper fastener driver for an installation to result in a water tight sealing of the structure and integrity of the structure. According to the MCA Technical Bulletin dated 8/28/2013 Version 1 “Proper Tools for Fastening Metal Panels” states “In any type of metal panel fastening application, screw guns with an adjustable clutch or a depth sensing nosepiece variable speed RPM of 0-2500, and a minimum of 6amps of power are recommended tools of choice to maintain integrity of the panel and building.” The correctly sized recessed magnetic driver socket to hold the screw in place during the installation process plays a part as well. Currently, a typical magnetic socket driver is good for up to driving 5,000 screws then should be replaced to maintain a snug screw head fit (be sure to clean out any accumulated metal filings in the driver socket during install prior to retirement). Secondly, the screw guns speed whether the screws are self driving or self tapping is very important for the best fastener installation outcome. As stated in the CSSBI Sheet Steel Facts 42 March 2015 “Fastening Prepainted Sheet Steel Roofing and Siding” “Whether using a self –drilling or tapping screw, the screw gun speed (RPM) is important. Slower screw gun speeds will improve the drilling performance by reducing the heat that is generated during the drilling process. For fastening sheet steel cladding in metal –to-metal or metal- to-wood conditions with carbon steel screws the maximum RPM recommended is 2500. Slower speeds may be advisable for drilling into thicker steel members or stainless steel screws. The screw manufacturer should be consulted.” Finally, the third ingredient is the tightening of the fastener which as further noted in the CSSBI Sheet Steel Facts 42 March 2015 “Fastening Prepainted Sheet Steel Roofing and Siding “article “It is important that the fastener be tightened correctly to obtain the optimum seal. Make sure the washer is compressed, but not so much that it is squeezed out the sides of the screw head. The screw manufacturer should be consulted.”
Both the Metal Construction Association (MCA) and the National Frame Building Association (NFBA) have concluded the use of these noted recommended variable screw gun speeds are optimal for fasteners to perform at their best.
Metal to Metal
(Carbon Steel or 410 Stainless Steel)
Steel Thickness Screw gun RPM
Less than ¼” 2,500 RPM maximum
¼” to ½” 2,000 RPM maximum
Metal to Wood
(304 Stainless Steel)
Steel Thickness Screw gun RPM
All thicknesses 2,500 RPM maximum
All thicknesses 1,000 RPM for self tapping