Rack
Rack turns up in 3 fields: gears, shop slang, mechanical. Here is what it means to the people in each one.
Rack in gears
A straight bar with gear teeth along it, which turns a pinion's rotation into straight-line travel.
A gear of infinite radius: teeth cut along a flat bar, with straight-sided flanks in the involute system. Meshed with a pinion, it converts rotary motion to linear or the reverse, as in steering gear, gantry drives and machine tool travel. The basic rack is also the reference profile that defines a whole gear tooth system, and generating cutters such as hobs are based on it.
"Gantry rack joints need to be set with a pitch gauge or the pinion will bump every time it crosses one."
Rack in shop slang
A heavy-duty framework of steel beams and uprights used to store materials and inventory.
A rack is an industrial storage structure designed to hold heavy loads, pallets, or long materials like pipes and lumber. Warehouses and workshops rely on these tiered systems to maximize vertical space and keep the floor clear of tripping hazards. Forklift drivers must navigate around them carefully, as a hard impact to a structural upright can bring the entire loaded framework down.
"Grab the forklift and pull that pallet of engine blocks down from the top rack."
Rack in mechanical
A straight bar with gear teeth cut into one face to translate rotational motion into linear motion.
A linear gear element that meshes with a rotating circular gear, known as a pinion. When the pinion turns, it drives the rack in a straight line, or conversely, pushing the rack turns the pinion. This mechanism is heavily used in steering systems, linear actuators, and machine tool slides to provide precise, high-force linear positioning.
"The carriage backlash is getting worse, so check if the teeth on the rack are worn down near the home position."