[W/K] :: Spiral gear

  Spiral \Spi"ral\, a. [Cf. F. spiral. See Spire a winding
     line.]
     1. Winding or circling round a center or pole and gradually
        receding from it; as, the spiral curve of a watch spring.
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     2. Winding round a cylinder or imaginary axis, and at the
        same time rising or advancing forward; winding like the
        thread of a screw; helical.
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     3. (Geom.) Of or pertaining to a spiral; like a spiral.
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     Spiral gear, or Spiral wheel (Mach.), a gear resembling
        in general a spur gear, but having its teeth cut at an
        angle with its axis, or so that they form small portions
        of screws or spirals.
  
     Spiral gearing, a kind of gearing sometimes used in light
        machinery, in which spiral gears, instead of bevel gears,
        are used to transmit motion between shafts that are not
        parallel.
  
     Spiral operculum, an operculum whih has spiral lines of
        growth.
  
     Spiral shell, any shell in which the whorls form a spiral
        or helix.
  
     Spiral spring. See the Note under Spring, n., 4.
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