Measures parallelism (non contact) between the anvil
and spindle faces. Replaces the use of Optical Parallel. Can be used from 25
mm to 300 mm range Micrometers. It employs the use of an Autocollimator that
could also be used for surface table calibration.
special Micrometer Anvil Checker designed and developed by Prisms India
replaces the use of many sets of Optical Parallel or Gauge Blocks/Slip
Gauges to cover a wide range of Micrometers.
Principle of working:
The light from the Autocollimator is divided into two parts by reflection
at the faces of a 90 deg prism, so that each part is directed towards one of
the gauging tips, the polished surface of which acts as a suitable
reflector. The angle between the reflecting faces of the prism is precisely
90 degrees, so that the two reflected beams are collinear. The light beam
are reflected at the anvil surfaces and re-enter the instrument after a
second reflection from the 90 degrees prism. Each beam forms a reflected
image of the scale, and if the anvils are parallel these images coincide;
otherwise the departure from parallelism is readily measured by reading the
separation of the images against the fixed scale. Moreover, the square ness
of the face of the micrometer spindle to the axis of rotation can also be
checked, by measuring any displacement of the appropriate image as the
spindle is rotated.
The prism is placed with the junction of its reflecting faces nominally
central with the instrument object glass, and with the faces in line with
the micrometer anvils. Displacement or tilt of the prism has no effect upon
measurement, but rotation of the prism (so that its edge is inclined to the
anvils) will produce a separation of the reflected images at right angles to
the micrometer axis. The prism must be adjusted rotationally until this
separation is a minimum. Any error in the 90 degrees angle between the
reflecting faces is doubled in its effect upon the reflected images, since
two reflections occur at each face.
The main advantage of this instrument is that, all sizes of Micrometer
ranging from 25 mm to 300 mm could be inspected for parallelism, whereas you
need to have gauge blocks or Optical parallel for every size of Micrometer.
The graduated reticule of the Instrument (MAC-01) reads 1 division = 0.923
microns (say 1 micron) Parallelism error of the spindle and the Anvil of the
Another model (MAC-02). is also available with least count of 0.739
Moreover this Instrument with Micrometer readout could also be used as an
Autocollimator for straightness, parallelism, squareness, Rotary table
MAC-01 - 3 arc secs/Micrometer Div , Range 3 meters, 14.5 microns per
MAC-02 - 1 arc sec/Micrometer Div, Range 4.5 meters, 4.83 microns per