BIFILAR a.
Two-threaded; involving the use of two threads; as, bifilar suspension; a bifilar balance. Bifilar micrometer (often called a bifilar), an instrument form measuring minute distances or angles by means of two very minute threads (usually spider lines), one of which, at least, is movable; -- more commonly called a filar…
MICROMETER n.
n which the two images are formed by the double refraction of rock crystal. -- Filar, or Bifilar, micrometer. See under Bifilar. -- Micrometer caliper or gauge (Mech.), a caliper or gauge with a micrometer screw, for measuring dimensions with great accuracy. -- Micrometer head, the head of a micrometer screw. -- Mi…