caster vs gear wheel

caster

noun
  • A wheeled assembly attached to a larger object at its base to facilitate rolling. A caster usually consists of a wheel (which may be plastic, a hard elastomer, or metal), an axle, a mounting provision (usually a stem, flange, or plate), and sometimes a swivel (which allows the caster to rotate for steering). 

  • The angle of the axis around which a car's front wheels rotate when the steering wheel is turned, with a vertical axis being defined as zero caster. 

  • A shaker with a perforated top for sprinkling condiments such as sugar, salt, pepper, etc. 

  • A stand to hold a set of shakers or cruets. 

  • Someone or something that casts. 

verb
  • To act as a caster 

gear wheel

noun
  • A wheel with a toothed rim, intended to engage with others, or similar equipment, to form a gear. 

How often have the words caster and gear wheel occurred in a corpus of books? (source: Google Ngram Viewer )