Impact Wrench (Structural Bolting)
CSI Division 05, Metals
A high-torque power tool that delivers rapid rotational impacts rather than continuous force, used during structural steel erection to drive and fully tension the final structural bolts once a connection has been aligned and temporarily held in place.
Why it matters
Structural bolts have to be tensioned to a specific, code-required level to perform correctly, and simply spinning a bolt tight by hand can't reliably reach that tension. An impact wrench provides the torque needed to properly tension a high-strength structural bolt, a step that's actually inspected and signed off on, not just a convenience over hand tools.
On a real project
Once an ironworker crew has aligned a connection with a spud wrench and set a few bolts by hand to hold it temporarily, they switch to an impact wrench to bring every bolt in that connection up to its required final tension.
Who this matters most to
An Ironworker finishes every permanent structural connection with an impact wrench, since the earlier hand-tool alignment steps are only meant to hold a connection temporarily, not to its final required strength.
Where this goes wrong
A crew leaves a connection's bolts snug but not fully tensioned with an impact wrench, planning to come back and finish it later, then loses track of which connections still need final tensioning. A special inspection finds bolts that were never actually brought up to their required tension.