Gage Blocks

Gage Blocks

Gage blocks are made with extraordinary precision to very tight tolerances. They can be combined to produce a wide range of sizes.

Gage blocks are made to standard grades:

  • 00 – Most exact tolerance
  • 0 – Suitable for inspection
  • AS -1 – Between shop floor use and inspection
  • AS-2 – General shop use


  • ANSI/ASME B89.1.9M (and the older U.S. Federal Specification GGG-G-15C). Former grades were AAA, AA, A, and B and .5, 1, 2, 3.
  • The Gauge Block Handbook (NIST)
Gage blocks are used in combinations to produce highly accurate size standards.

Gage blocks must be wrung together to produce accurate results.

Gage blocks wrung together to produce a 1.8000 length standard.

A note about spelling: ASME B89.1.9-2002 (R2012) uses the “gage” spelling. The NIST classic text “The Gauge Block Handbook” uses (obviously) the “gauge” spelling. Because the gage spelling is used in the standard, we have adopted that form here.