Metric Hex Screwdriver

The straight-shaft hex in a screwdriver format. Same hex tip as the T-handle and Y-handle hex tools in the line, on a long-axis screwdriver handle that reaches into the deep-recess fasteners a cross-bar handle can't enter. Available individually across the metric hex sizes the 620 line covers.

The straight-shaft format is the right call for two situations: where the bolt sits below a recess that a T-handle's cross-bar would foul against, and where a long-axis grip lets you hold the tool perpendicular to the work surface for the final torque pass. Stem cap bolts under a recessed top cover, derailleur limit screws sunk behind a guard, brake-pad retention bolts inside a caliper. These are the fasteners that need a screwdriver shape rather than a T or Y.

The chrome-vanadium shank is hardened and tempered, with a black-oxide tip for corrosion resistance and a clean fit into the hex recess. The handle is a three-material composition: a hard core for torque transmission, a softer outer for comfort under repeated use, and a hex bolster at the base for wrench-assist torque on the high end of the working range. The shank length is sized for bike-fastener reach, long enough to access recessed bolts and short enough to fit on a tool rack without sag.

Compatibility

The 620 line covers the bike-relevant metric hex span, sized per individual order:

• 2.5 mm: disc-brake caliper banjo bolts on some hydraulic systems
• 3 mm: older shifter and brake-lever pinch bolts
• 4 mm: stem face-plate bolts; brake-lever clamps; bottle-cage bolts
• 5 mm: stem steerer-clamp bolts; seatpost binders
• 6 mm: disc-brake caliper-mount bolts; some chainring bolts
• 8 mm: pedal threads from inside; some crank-fixing bolts
• 10 mm: Campagnolo crank-spindle bolts

The straight-shaft format earns its place when access geometry rules out a T-handle. For the most-reached sizes (4, 5, 6 mm), most shops keep a straight-shaft screwdriver alongside a T-handle of the same size; the two formats cover different access conditions on the same fastener.

Specs

• Single-size straight-shaft hex screwdriver (size selected at order)
• Chrome-vanadium steel shank, hardened and tempered
• Black-oxide tip treatment for corrosion resistance and recess fit
• Three-material composition handle
• Hex bolster at the handle base for wrench-assist torque
• Trivalent chrome plating to ISO 1456:2009 on the non-tip shank surfaces
• Hex tip manufactured to the ISO 2936 dimensional standard for metric hex keys
• Manufactured in Slovenia

Built in Zreče, Slovenia

Unior has been forging hand tools in Zreče since 1919, and sponsors professional road and mountain-bike race teams. The straight-shaft hex screwdriver is the same hex-tip geometry as the T-handle and Y-handle hex tools in the line, on a different handle format; the construction and dimensional tolerances are shared across formats.

Pro tip from our mechanics

A screwdriver-format hex doesn't replace a T-handle or Y-handle; it adds a third format that covers the access conditions the other two can't. The fastener layouts most likely to need this tool: derailleur limit screws on rear mechs where a guard sits behind the bolt, brake-pad retention bolts that pass through the caliper body, stem cap bolts on bikes where the steerer cover sits proud of the surrounding bezel.

For when the straight-shaft hex format beats a T-handle or Y-handle, and the access-condition decision tree for the most-reached bike hex sizes: Hex and Torx wrenches: how to pick the right tool for the job →.