Impact drivers and wrenches

An impact wrench is a socket wrench power tool that delivers high rotational torque and high torque output with minimal effort. It is great for tightening and loosening bolts, lug nuts and rusted fasteners. 

Impact wrenches and impact drivers may look similar to each other, but they are better suited for different applications. Impact wrenches typically use a square drive – available in several sizes – and are designed to deliver higher impact force. That extra power often makes impact wrenches heavier, but it also makes them better suited for tougher jobs where more power, or torque, is required. This includes fastening larger anchors, hex-head bolts, nuts, lag screws, or tackling extremely tight, or rusted fasteners.

Impact drivers, on the other hand, come with a 1/4" hex collet that accepts 1/4" hex‑shank bits. They tend to be more about speed than power and are more suited to smaller projects.

For light fastening especially in tight spaces, choose the SIW 2-A12 or SIW 4R-22. 


For light to medium anchoring, including common bolt and anchor work, use SIW 4AT-22 or SIW 6AT-22.

For heavy‑duty bolting and structural anchoring, the SIW 8-22 and SIW 10-22 models provide the power you need.

If your anchors require pre-tension according to approvals, select SIW models that support the SI‑AT module.

The SI‑AT module helps ensure approved Hilti anchors and installation elements are set correctly and consistently. It automatically applies the right pre‑tension based on the approved ETA or ICC settings, so your installation meets the required standards every time.

It also records each fastening, making it easy to provide documentation for inspections or quality checks.

Please note: the SI‑AT module does not measure or apply an exact torque value. Instead, it helps ensure installation is carried out according to the approved setting parameters.

The power of an impact wrench is measured in torque. For light anchoring or smaller bolting tasks, a more compact wrench – such as the SIW 4AT-22 or SIW 6AT-22 – provides enough torque. Heavy bolting and structural work require higher‑torque models like the SIW 8-22 or SIW 10-22. Always match the torque output of the tool to the application requirements.

Hilti impact wrenches are available with either friction‑ring or detent‑pin anvils.

Friction‑ring anvils allow quick, easy socket changes and are used on the SIW 4R‑22, SIW 6AT‑22, SIW 8‑22 and the SIW 10‑22. Some are designed for simple on‑site replacement to help you reduce downtime.

Detent‑pin anvils offer maximum socket retention for overhead or vibration‑intensive applications, and are used on the SIW 4AT‑22.

Using non‑impact-rated sockets: Chrome sockets can crack or shatter under impact load.

Over‑tightening: An impact wrench will continue to tighten as long as the trigger is pulled.

Using an impact wrench for exact torque: When exact torque is required, use a torque wrench to verify. When approval‑compliant installation is required, use the SI‑AT module.

Using the wrong torque class: Too little power can leave bolts under-tightened, while too much can cause damage.