Sockets and wrenches: drive size, points and material

Start with drive size

A 3/8-inch drive set covers most fasteners on a car: brackets, covers, hose fittings and interior bolts. 1/2-inch is for the ones that need leverage, such as wheel nuts, suspension arms and mounts, and 1/4-inch is for trim and small screws where a larger ratchet will not fit at all.

A set built around one drive size is more useful than a mixed box, because the ratchet, extensions and universal joints then fit each other.

• 3/8-inch: engine bay, body and general work.
• 1/2-inch: wheels, suspension and anything rusted.
• 1/4-inch: interior, trim and small fasteners.

Six-point or twelve-point

Twelve-point sockets are easier to line up on a fastener you cannot see, and they fit twelve-point heads. The trade is contact area: on a rusted or soft nut, a twelve-point socket is more likely to round the corners.

Six-point sockets put metal on the flats and hold on longer. On a car that sees road salt, six-point is the safer default, with a dedicated damaged-nut socket for the ones already rounded.

• Six-point: more contact area, fewer rounded nuts.
• Twelve-point: quicker to seat, better on twelve-point heads.
• For a damaged nut, use a flank-drive or bolt-grip socket rather than forcing the size.

Material decides what can drive it

Chrome sockets are hard and thin, which is what you want in the hand. Impact-rated sockets are softer and thicker so they absorb the shock of a power tool rather than cracking under it.

A chrome socket on an impact wrench is the classic way to break one, and the pieces travel. Keep the two sets in separate trays so the choice is deliberate.

Where a wrench beats a socket

A ratcheting combination wrench turns a fastener where there is no room for a socket and ratchet: a caliper bracket, a tensioner, a fitting behind the engine.

Use it for turning rather than for breaking a seized fastener free. That first movement is a breaker bar job, and the ratchet mechanism is the part that fails if it is used for it.