TM 9-243 TYPES AND USES Ring and snap gages and precision gage blocks are used as standards to determine whether or not one or more dimensions of a manufactured post are within specified  limits.  Their  measurements  are  included  in  the construction of each gage, and they are called fixed gages. However, some snap gages are adjustable. Gages are used for a wide range of work, from rough machining to the finest tool and die making. The accu- racy  required  of  the  same  type  of  gage  will  be  different, depending on the use. SNAP   GAGE   -   ADJUSTABLE RING GAGES SNAP GAGE - NONADJUSTABLE The  following  classes  of  gages  and  their  limits  of  accu- racy are standard for all makes: Class  X  -  Precision  lapped  to  close  tolerances  for  many types of masters and the highest quality working and  inspection  gages. Class  Y  -  Good  lapped  finish  to  slightly  increased  toler- ances for inspection and working gages. Class Z - Commercial finish (ground and polished, but not fully lapped) for a large percentage of working gages in which tolerances are fairly wide, and where production quantities are not so large. Class ZZ - (Ring gages only). Ground only to meet the demand for an inexpensive gage, where quantities are small and tolerances liberal. GAGE  BLOCKS The table below lists the tolerances for ring gages in each class: TO  AND ABOVE INCL X 0.029 0.825 0.00004 0.825 1.510 0.00006 1.510 2.510 0.00008 2.510 4.510 0.00010 4.510 6.510 0.00013 6.510 9.010 0.00016 9.010 12.010 0.00020 Y 0.00007 0.00009 0.00012 0.00015 0.00019 0.00024 0.00030 RING GAGES Z ZZ 0.00010 0.00020 0.00012 0.00024 0.00016 0.00032 0.00020 0.00040 0.00025 0.00050 0.00032 0.00064 0.00040 0.00080 X Precision   lapped Y Lapped Z Ground or polished (grinding marks may be in evidence), ZZ  Ground  only 15-2