Re: In-House Calibration of Thread Plugs/Rings to achieve a 4:1 Ratio
Well a standard measuring machine and a set of thread wires will give you a 4:1 for the thread plugs, including "W" class.
A "W" class setting plug will calibrate most of your working rings.
A Universal Measuring Machine like a SIP305M, Pratt and Whitney Universal Labmaster or Mahr 828CiM with the ruby dumbell stylus will measure your W class rings.
Also check ouut the Johnson Threadview system as it will measure many of these parameters.
Sorry the reply was so late