Williams 401SPW Single Setting Torque Screwdriver (4-40 in-lb)

Description

The Williams 401SPW is a single-setting torque screwdriver with a trilobular comfort grip and a universal 1/4″ hex bit holder with a rare-earth magnet to keep bits seated. An internal cam-over clutch slips at the set torque, so the screwdriver stops transmitting torque once the fastener is properly seated rather than relying on operator feel.

Range: 4-40 in-lb. This is the unset (“401SPW”) version, adjustable by the operator; Williams also offers this same screwdriver factory pre-set to a fixed torque with its own calibration certificate (model 401SP-SETW) for production lines that shouldn’t have the setting changed on the floor.

This capacity range is built for small-fastener work — electronics assembly, instrument panels, small machine screws — where a full-size torque wrench is impractical and a consistent, repeatable stop matters more than raw capacity.

**Frequently asked questions**

**How does the cam-over clutch work?** At the set torque, the internal clutch “cams over” and slips rather than transmitting further torque to the fastener — this protects small screws from over-tightening and gives a consistent stopping point regardless of how hard the operator keeps pushing.

**Does it need periodic recalibration?** Yes — annually is typical, or per your quality system’s interval, since the internal clutch spring can drift with heavy use.

**What bits does it accept?** A universal 1/4″ hex bit holder with a rare-earth magnet accepts any standard 1/4″ hex driver bit.