keyway

IPA/ˈkiː.weɪ/
IPA/ˈkiː.weɪ/

keyway — noun

  • keywaysingular
  • keywaysplural

1. a long, narrow slot cut into a shaft or wheel so that a small metal piece called

1.nounC2
Definition

a long, narrow slot cut into a shaft or wheel so that a small metal piece called a key can sit inside it and lock the two parts together when they turn.

Example

Shirin used a milling machine to cut a keyway along the steel shaft.

cut a keyway along + shaft (typical workshop action)

The mechanic checked that the keyway in the pulley lined up with the slot on the motor shaft.

keyway in [wheel/pulley] + lined up with + slot on shaft

Common collocations
  • cut a keyway
  • machine a keyway
  • keyway depth
  • keyway width
  • matching key and keyway
Synonyms
  • key seat

    near-equivalent technical term, more common in American engineering texts

  • key slot

    informal alternative used by mechanics; less standard in engineering drawings

Grammar Patterns

a keyway in [machine part]

cut a keyway

Usage Note

Subject is usually a machine part with a rotating shaft (pulley, gear, fan blade, pump rotor). The matching metal piece that fits inside is itself called a 'key', so the two words almost always appear together.

Common Mistakes

I lost the keyway to my house.
I lost the key to my house.
a 'keyway' is a slot inside a machine, not the metal object you carry around or put into a lock.

Word family

Synonym discussion

Sense: noun/1

All four words describe a cut feature in a rotating part that stops a wheel or gear from slipping on its shaft, but they are not interchangeable in formal engineering writing. 'Keyway' is the standard term in British and international machine-design drawings; it refers specifically to the long narrow groove that holds a single rectangular or square metal key. 'Key seat' is the preferred term in American mechanical engineering and often refers to the groove cut into the shaft itself, with 'keyway' reserved for the matching groove in the surrounding wheel — for example, 'the key seat in the motor shaft mates with the keyway in the pulley hub'. 'Key slot' is a more casual workshop word used by mechanics in conversation; it would not normally appear on a technical drawing. 'Spline' is different in kind: a spline is a series of many small ridges and grooves cut all around the shaft, not a single keyway, and it carries torque without any separate metal key.

keyway ↗key seatkey slotspline ↗

Common collocations

Nouns

  • keyway depth
  • keyway width
  • keyway cutter
  • shaft keyway
  • pulley keyway

Phrases

  • cut a keyway
  • machine a keyway
  • the key fits into the keyway

Prepositions

  • keyway in [the shaft / the pulley / the hub]
  • keyway along [the length of the shaft]

Etymology

Old EnglishEnglish

Formed in nineteenth-century English engineering by joining 'key', meaning a small wedge-shaped piece that locks two parts together, with 'way', here in the older mechanical sense of a guiding channel or groove (as in 'slideway' or 'gateway'). The compound appears in workshop manuals from the mid-1800s as steam-engine and railway-axle design created the need for a precise name for the slot that holds a shaft key.