Gauge Blocks

The collection carries three Mitutoyo 516 Series gage block sets, each available in multiple configurations. The lineup covers inch rectangular sets (35-piece and 81-piece), metric 1mm rectangular sets (47 to 112 pieces), and inch square sets which are all available in either steel or Mitutoyo's CERA ceramic material. Across the three product families, buyers can select from multiple grades (AS-0/Grade 0, AS-1, AS-2, and Grade K) to match their specific accuracy and application requirements.

Gauge blocks also known as gage blocks or Johansson blocks after their inventor are precision-machined rectangular or square blocks manufactured to exact nominal lengths with extremely tight tolerances on flatness and parallelism. They serve as the physical reference standards that connect shop floor measurements back to the international definition of the metre. When you calibrate a micrometer, set a snap gauge, or verify a comparator, you are comparing your instrument against a gauge block whose length is traceable through an unbroken chain to national metrology standards. Without traceability to certified gauge blocks, any measurement you make cannot be defended as accurate in an audit or quality system.

The inch rectangular sets follow the standard ASME/ANSI B89.1.9 inch increment system, with the 81-piece set providing full coverage from 0.1001" up to 4" and the 35-piece set covering a more compact range. The inch square sets use the same inch increment system but feature a square cross-section geometry rather than rectangular, square blocks offer a larger wringing surface area and are preferred by some labs for stability in stacked configurations. The metric 1mm sets follow the ISO/JIS metric increment system based on 1mm steps, with set sizes from 47 to 112 blocks covering ranges from 1.001mm up to 100mm, designed for metric-based measurement environments and international quality systems.

Grade designations define the dimensional tolerance band that each block is manufactured to, with tighter grades commanding higher accuracy. Grade K (also referred to as Reference or Calibration grade) is the most precise, used as laboratory reference standards to calibrate Grade 0 and lower sets. Grade AS-0 (Grade 0) is a high-accuracy inspection grade used in metrology labs and quality rooms to calibrate working standards and verify instruments. Grade AS-1 is a precision inspection grade suitable for quality control rooms and demanding production inspection. Grade AS-2 is a workshop grade appropriate for everyday production floor use where the highest precision is not required. Selecting the right grade depends on your measurement uncertainty budget and the downstream instruments you need to calibrate or set.

Wringing is the phenomenon by which two gauge block measuring faces, when cleaned and slid together with slight pressure, adhere to each other with enough force to support the weight of the second block without mechanical fasteners or adhesives. This adhesion is caused by molecular attraction and the near-perfect exclusion of air between two ultra-flat, ultra-smooth surfaces. It allows multiple blocks to be stacked into a precise composite length for example, combining a 1.003" block with a 0.100" and a 0.250" block to produce exactly 1.353". For wringing to work reliably and without introducing measurement error, the wringing surfaces must be lapped to exceptional flatness and parallelism. Mitutoyo's 516 Series is manufactured to deliver consistent, reliable wringeability across all grades and materials.

Steel gauge blocks are the traditional standard, offering excellent durability, familiar handling characteristics, and broad compatibility with standard gauge block accessories. They require careful maintenance to prevent rust and corrosion, particularly in humid shop environments. Mitutoyo's CERA ceramic blocks (zirconia-based) offer several practical advantages: they are non-magnetic, non-conductive, corrosion-resistant, and approximately 30% harder than steel resulting in longer wear life and reduced susceptibility to surface damage. CERA blocks are also thermally stable and do not exhibit the burring that can occur on steel blocks over time. For calibration laboratories and clean room environments, ceramic is increasingly the preferred material. Steel remains the practical choice where cost, familiarity, or specific accessory compatibility are factors.

The right set size depends on the range of reference dimensions you need to build and the resolution required. Smaller sets (35 to 47 pieces) cover a more limited range with larger increments between blocks, sufficient for general workshop calibration and snap gauge setting. Mid-size sets (56 to 87 pieces) provide finer increments and wider coverage, allowing you to build a broader range of composite lengths for inspection room use. The largest sets (81-piece inch, 87-piece metric, up to 112-piece metric) provide the finest increment resolution including 0.0001" or 0.001mm steps needed to build virtually any reference dimension with minimal wringing combinations. Calibration labs and metrology departments generally require the largest, highest-grade sets to maintain full traceability of their working instrument fleet.

Traceability means that the length of each gauge block can be related back, through an unbroken chain of calibrations, to the national or international definition of the unit of length ultimately the SI metre. Each Mitutoyo 516 Series set ships with a manufacturer inspection certificate documenting that the blocks have been measured against standards that are themselves traceable. In regulated industries such as aerospace (AS9100), automotive (IATF 16949), medical devices (ISO 13485), and defense, traceability of measurement standards is a mandatory requirement of the quality management system. Using gauge blocks without a valid, traceable calibration certificate creates an audit nonconformance and potentially invalidates every measurement made using instruments calibrated against those blocks.

The Mitutoyo 516 Inch Square Gage Block Set uses the same inch increment system and grade structure as the rectangular sets but features a square cross-section. Square blocks offer a larger contact area on each measuring face, which some metrology labs prefer for increased wringing stability in tall stacked combinations and for use with certain gauge block holder accessories and angle plate configurations. The ceramic (AS-0) and steel (AS-2) options are available, making the square set suitable for calibration lab and inspection room use respectively. The choice between square and rectangular is largely application-driven rectangular blocks are the dominant standard for most applications, while square blocks are specified by labs with specific accessory requirements or handling preferences.

All Mitutoyo gauge block set orders ship free to the continental USA, backed by a best-price guarantee. Every set includes a manufacturer inspection certificate and ships in a precision fitted storage case. A 30-day return policy and Affirm financing at checkout are also available. Government and institutional buyers including calibration labs, defense contractors, and metrology departments can submit an RFQ through the dedicated Government RFQ page. For help selecting the right grade, material, set size, or unit system for your quality system requirements, call or text Gustavo directly at 617-398-7852, Monday through Friday, 8am–5pm EST.