spindles

Spindles are the plural form of spindle, a term used in several fields to describe slender, rod-like objects or devices that serve distinct functions. Common meanings appear in biology, textile crafts, and mechanical engineering.

In biology, the spindle apparatus is a microtubule-based structure that forms during cell division to separate chromosomes. It comprises microtubules, motor proteins, and two poles, with kinetochores attaching chromosomes to spindle fibers. In animal cells, spindle poles typically derive from centrosomes; many plants and fungi assemble spindles without centrioles. During metaphase, chromosomes align at the cell's equator; in anaphase, sister chromatids are pulled apart as microtubules shorten and motor proteins drive poleward movement. Checkpoints monitor proper attachment before progression.

In textile arts, a spindle is a rod used to twist and wind fibers into yarn. Drop spindles are handheld and come in different weights; traditional spindles and spinning wheels both enable fiber turning into thread. Yarn properties depend on fiber type, twist, and spinning technique.

In machinery, a spindle is the rotating shaft that holds cutting tools or workpieces. Spindles can be belt-, gear-, or direct-driven and usually incorporate bearings, cooling, and a tool-mounting taper. Spindle speed, rigidity, and balance affect machining accuracy in lathes, milling machines, and similar equipment.