This British Standard specifies the limits of size for the following types
of gauges, setting plugs and check plugs for the various classes of
standard Unified Coarse (UNC), Unified Fine (UNF) and Unified Extra
Fine (UNEF) threads specified in BS 1580-1.
a) GO and NOT GO screw gauges:
1) screw plug gauges;
2) solid screw ring gauges;
3) adjustable screw ring gauges;
4) adjustable screw calliper gauges.
b) Setting plugs for GO and NOT GO adjustable screw ring gauges and
for GO and NOT GO adjustable screw calliper gauges:
1) double length type;
2) single length type.
c) GO and NOT GO check plugs for solid screw ring gauges.
d) GO and NOT GO plug gauges and GO and NOT GO calliper gauges for
the crest diameters of product threads.
NOTE The values tabulated in this standard have been derived from the
application of the tolerances specified in BS 919-1 to the limits of size
given in BS 1580, and reference should be made to the former standard
for general information, details of the form of thread for Unified screw
gauges, and tolerances on pitch and thread angle.