Ratchet

A ratchet is a mechanical device that allows continuous motion in one direction while preventing motion in the other. In hand tools, a ratchet lets you tighten or loosen a fastener without lifting the tool off between strokes — you swing the handle back and forth, and the mechanism does the rest.

How it works

Inside a ratchet, a toothed gear is paired with a spring-loaded pawl. The teeth are asymmetrical — one edge is gently sloped, the other steep. In the free direction, the pawl slides over the gentle slopes with an audible click. In the locked direction, the pawl jams against the steep face, and the gear, pawl, and housing become a solid unit that transfers the handle’s force to the fastener.

Key specifications

• Tooth count: More teeth mean a smaller swing arc needed to engage the next tooth. A 72-tooth ratchet needs only 5° of swing; a 36-tooth needs 10°.
• Drive size: 1/4-inch, 3/8-inch, 1/2-inch — determines which sockets fit.
• Head size: Affects access in tight spaces. Slim-head ratchets are designed for engine bays.

Types

• Fine-tooth ratchet: 72 or more teeth for minimal swing arc — essential in tight spaces.
• Standard ratchet: 36 to 48 teeth — adequate for general work, more durable under heavy loads.
• Flex-head ratchet: The head pivots, allowing the handle to be angled away from the fastener for better access.
• Gearless ratchet (roller clutch): Uses a roller mechanism instead of a pawl, providing smooth, silent operation with zero backlash.

The direction switch

Every ratchet carries a small flip lever — usually in the head — that reverses which way the pawl locks. Flip it one way and clockwise strokes tighten; flip it the other and the same tool loosens without leaving the fastener. A stuck or mushy switch is the most common ratchet repair: it usually means the detent ball and spring under the lever have grit or wear, not a broken pawl.

Ratchet vs. breaker bar

The ratchet’s pawl and gear are precision parts sized for turning, not for shock. To crack loose a corroded bolt, mechanics reach for a breaker bar — a plain, non-ratcheting handle with the same drive square. It has no mechanism to damage, and its extra length multiplies torque. Using the ratchet to break tight fasteners loose is the fastest way to round its gear teeth or snap the pawl spring; the click-click of a skipping pawl under heavy load is the sound of that damage happening.