A nut driver is a hand tool used to tighten or loosen hex nuts and hex-head bolts. It looks like a screwdriver, but the tip is a hollow socket that fits around a nut instead of a blade that fits into a slot. Nut drivers matter in electronics, appliances, bicycles, lab equipment, and workshop assemblies because they give quick, centered control on small fasteners.
They are especially useful when a nut sits on a threaded stud and cannot be reached easily with a flat wrench.
Key Facts
- Torque is the turning effect of a force: τ = rF when the force is applied perpendicular to the handle radius.
- A larger handle radius lets the same hand force produce more torque on the nut.
- Nut driver size is measured across the flats of the hex opening, such as 1/4 in, 5/16 in, 8 mm, or 10 mm.
- A hollow shaft allows the threaded stud to extend into the tool while the socket grips the nut.
- For a snug fit, the socket size must match the nut's across-flats dimension, not the outside corner-to-corner distance.
- Overtightening can strip threads, round nut corners, or crack plastic and electronic parts.
Vocabulary
- Nut driver
- A hand tool with a screwdriver-style handle and a hollow socket tip used to turn hex nuts and hex-head bolts.
- Socket tip
- The hollow hex-shaped end of a nut driver that fits around the nut to apply turning force.
- Torque
- The twisting effect produced when a force acts at a distance from an axis of rotation.
- Hex nut
- A six-sided fastener with internal threads that screws onto a bolt or threaded stud.
- Hollow shaft
- An open center section in some nut drivers that lets a long bolt or stud pass inside the tool.
Common Mistakes to Avoid
- Using a socket that is slightly too large, because it can slip and round the corners of the nut instead of gripping the flat faces.
- Pushing the nut driver at an angle, because misalignment reduces contact area and can damage both the nut and the socket tip.
- Assuming more force is always better, because overtightening can strip threads or crush the material being fastened.
- Measuring the nut across its corners, because nut driver sizes match the distance across opposite flat faces.
Practice Questions
- 1 A student applies a 35 N force perpendicular to the edge of a nut driver handle with an effective radius of 0.018 m. What torque is applied to the nut?
- 2 A nut driver requires 1.2 N m of torque to loosen a nut. If the effective handle radius is 0.020 m, what perpendicular force must the user apply?
- 3 A 10 mm nut driver slips on a hex nut, but a 9 mm nut driver will not fit over it. Explain what this suggests about the nut size, tool choice, or possible damage to the nut.