Inspec Insights

About Gage Blocks

Set of 36 gage blocks carbide or steel


     Gage blocks are a staple of machine shops, measurement labs, factories, and anywhere else a precision measurement reference is needed.  Gage blocks (or “gauge” blocks) can serve as a simple go/nogo gage, or be used to calibrate other equipment, such as micrometers, calipers, or dial indicators.  Multiple gage blocks can be stacked to verify a height gage.  They are the main means for achieving length standardization within modern manufacturing and industry.

     Gage block surfaces are ground and lapped to size for accuracy, but the lapped surfaces also allow multiple gage blocks to be wrung together.  The wringing process involves cleaning the gage block surfaces and rubbing or rotating the two blocks together, along their longest and widest surface, until they stick to each other.  The feel is similar to two surfaces clinging together magnetically, but no magnetism is needed.  The wringing process allows for a near zero clearance between multiple gage blocks, reducing stack up errors.  Ideally, when wringing gage blocks together, you should strive to use the fewest blocks needed to achieve the required length.

     Gage block grades can be a bit confusing to those that are unfamiliar with the different standards.  Block grades scales are set by JIS (Japan), ASME (US), BS (UK) or DIN (Germany), in addition to the US Federal specifications.  Inspec Inc. offers this Gage Block Tolerances and Material Specifications, based on the ASME B89.1.9-2002 Standard.  Print it out and put it in your toolbox or on your tool crib wall!

     A variety of materials are used for the construction of gage blocks, with steel alloys and carbide (either chromium or tungsten) being the most common.  However, ceramics and even glass are used in special applications.

You may know that gage blocks can also go by the name “slip gauges”, as the individual blocks are also called “slips”.  This is sometimes associated with the term “slip fit”, although there is some confusion as to the origins of the term.  However, a more traditional name is “Jo Block”, named after the person credited with inventing them; Carl Johansson, a Swedish machinist. 

Whatever you like to call them, Inspec Inc. can provide you with the appropriate grade gage blocks for your application.  When you purchase from Inspec, you are buying from an A2LA accredited facility.  We sell individual gage blocks, as well as complete sets, with inch or millimeter markings, in steel or carbide.  Inspec Inc. will also notify you when your gage blocks are due for calibration (if you choose) and can provide certification to ISO 17025 standards.  Please see our complete gage block selection HERE, in our store. 

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