We Have Resurfaced Granite Surface Plates from California to North Carolina to Mexico

 The  Dark areas are as  result of normal use. Note the wear areas are on
 both sides of the
plateThis  is  good  and  indicates that  the Inspector
is using different areas to prevent major wear in one area.  These wear
areas are only a few tenth's, ( .0001's ),  however if all of this wear was
to occur in one  place,  it would  be  thousandths,  ( .001's)  of  an inch.

After lapping, all of the plates are inspected using a repeat-o-meter.
This  simulates an indicator  on a height stand  but uses a  .000010
resolution indicator  to  determine the ability  to  duplicate a  reading
anywhere on this surface.   This is only  one  half  of  the  calibration
procedure  due  to the  fact  that a repeat-o-meter can not determine
flatness, only repeatability.

An Autocollimator is used to measure the flatness of the surface plate.
 This instrument uses collimated  light that is bounced off of a mirror mounted
on a  sled  selected  for  its  pad spacing. Sleds work like sine bars and convert
arc. seconds into millionths of an inch, rise or fall when moved in increments
equal to the pad spacing. This data is assembled into an actual contour plot of
the surface plate and calculates the  overall  flatness.


This information is used to produce a   Certificate of Calibration
that is traceable to NIST and compliant to ISO/IEC 17025-2005,
ISO 9001-2000, Mil.Std.45662, ANSI/NCSL Z 540-1 & TS 16949.
This Cert. references the tolerances in the Federal Spec. GGG-P-463c
The "actual flatness" Validates  compliance  to these  tolerances.
This Cert is a real tool that gives you relevant information that allows
 you to use your surface plate to its full potential.