Screwdrivers, Nut Drivers and Hex Keys

Tip type and size: the fit that protects the screw head

Most damaged screws come from the wrong tip. Phillips tips come in numbered sizes (PH1, PH2, PH3), and Pozidriv is a different, similar-looking profile that a Phillips driver grips poorly. A slotted driver should fill the slot's width and thickness. Torx uses a star with T-numbers, where T9 is much smaller than T40, and square and hex profiles have their own sizes. Match the tip to the head before thinking about handle or price.

Nut drivers, hex keys and bit systems: one handle or many

Nut drivers are hex sockets on a handle, used for hex-head screws and small nuts, and a hollow shank lets them run down over a long threaded stud. Hex keys are sold in inch fractions or in millimeters; a metric key in an inch socket, or the reverse, may turn but will round the corners. Ball-end keys reach at an angle but carry less torque than the straight end, and folding sets keep the sizes together.

Multi-bit and ratchet screwdrivers keep several tips in one handle, which saves space but adds a joint where play can creep in. Sets are described by piece count, and the count often includes bits and extensions as well as drivers, so read what is in the case. For electrical work, drivers sold as insulated carry a voltage rating on the handle, normally 1000 V, and a damaged coating removes that protection.

Questions about Screwdrivers, Nut Drivers and Hex Keys

What is the difference between Phillips and Pozidriv?

Pozidriv has extra small ribs between the arms of the cross and a blunter tip, so it grips more firmly and slips less. A Phillips driver in a Pozidriv screw, or the reverse, fits loosely and chews the head. Look for the PH or PZ prefix in the size.

How do I read a size like T9-T40 on a Torx set?

The T number is the size of the star-shaped tip, and a higher number means a larger tip, so a T9 to T40 set runs from small fasteners to large bolts. Tamper-resistant Torx screws have a pin in the recess and need a bit with a matching hole.

Are ball-end hex keys as strong as standard ones?

Not at the ball end. The rounded tip contacts the socket at fewer points, so use it to start or run a screw at an angle and switch to the straight end for final tightening or loosening a stubborn one. Excess torque on the ball end can deform it.