The regularity for recalibrating a set of gage blocks is not standardized. However, overseeing entities, such as American National Standards in Dimensional Metrology (ASME) and Federal standards do suggest a particular period of time after which you ought to recalibrate your gage blocks. The higher the grade of your gage blocks, the more infrequently you can recalibrate them. Gage blocks with a grade of 0.5 or 1 will usually be recalibrated once a year or annually. Gage blocks with a grade of 2 or 3 are typically recalibrated semi-annually or as often as monthly. Once you reach the level of master blocks, since they are not used as commonly as other grades of gage blocks, the typical length of time between calibrations is about 2 years. As a general rule, the regulatory power for matters such as recalibration rests on the shoulders of agency inspectors, rather than the National Institute of Standards and Technology (NIST).