Why should Impact Drills not be used with ASSY Self-Tapping screws?

Impact Drills cause a torque differential to the ASSY self-tapping screws, which causes permanent damage to the screw during installation.
Drilling in self-tapping ASSY screws with an impact drill is not recommended. When using an impact drill with the screws, a torque differential between the screw head and the screw tip is exerted. Higher torque is usually exerted to the head of the screw and less torque transmitted to the screw tip. This differential is especially important when drilling in longer screws.
The torque differential causes the screw to be pre-stressed well before it is fully installed, reducing the capacity of the screw.  The higher torque on the screw head can cause the screw head to pop off and permanently damage the screw. Given all of the above, it is recommended to use a drill with a low rpm and high torque as presented here: Which Drill Should Be Used to Install Assy Fasteners?

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Relevant Technical Resources

Gallery canadian screw design guide cover Canadian Structural Screw Design Guide
Gallery dg   assy fastener catalog cover American Structural Screw Design Guide

Products Covered in this Article

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Gallery eco a2 ASSY Eco Stainless Steel
Gallery assy fwh explosion resized ASSY FWH Flat Washer Head
Gallery assy kombi explosion resized ASSY Kombi
Gallery kombi a2 ASSY Kombi Stainless Steel
Gallery sk a2 ASSY SK Stainless Steel
Gallery assy sk explosion resized ASSY SK Washer Head
Gallery assy vg csk explosion resized ASSY VG CSK Counter Sunk Head
Gallery assy vg cyl explosion resized ASSY VG CYL Cylinder Head
Gallery assy vg rh explosion ASSY VG RH Reverse Head

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