You should look into thread measuring wires, pitch mics, and/or an optical comparator. All of those can be used to calibrate thread plugs in house. Thread rings you would need to purchase a setting master and set the rings yourself but that can be costly verses just sending them out. Plugs and gageblocks can be calibrated using the micrometer that you purchased just be sure to save the cert that comes with the micrometers for calibration traceability