A Go-No gauge (or Go/no go) refers to an inspection tool used to check a workpiece against its allowed tolerances.
Its name derives from its use: the gauge has two tests; the check involves the workpiece having to pass one test (Go) and fail the other (No Go).
It is an integral part of the quality process that is used in the manufacturing industry to ensure interchangeability of parts between processes,
or even between different manufacturers.
A Go NoGo gauge is a measuring tool that does not return a size in the conventional sense, but instead returns a state.
The state is either acceptable (the part is within tolerance and may be used) or it is unacceptable (and must be rejected).
They are well suited for use in the production area of the factory as they require little skill or interpretation to use effectively
and have few, if any, moving parts to be damaged in the often hostile production environment.

These gauges are referred to as plug gauges; they are used in the manner of a plug.
They are generally assembled from standard parts where the gauge portion is interchangeable with other gauge pieces
(obtained from a set of pin type gauge blocks) and a body that uses the collet principle to hold the gauges firmly.
To use this style of gauge, one end is inserted into the part first and depending on the result of that test, the other end is tried.[1]

A set of pin from 1.550 - 6.725 mm
In the right hand image, the top gauge is a thread gauge that is screwed into the part to be tested,
the labeled GO end will enter into the part fully, the NOT GO end should not.
The lower image is a plain plug gauge used to check the size of a hole, the green end is the GO,
red is the NO GO. The tolerance of the part this gauge checks is 0.30mm where the lower size of the
hole is 12.60mm and the upper size is 12.90mm, every size outside this range is out of tolerance.
This may be initially expressed on the parts drawing in a number of styles, three possibilities may be:
12.75mm +/- 0.15mm
12.60mm +0.30 -0.00
12.90mm +0.00 -0.30

Gauge blocks (also known as gage blocks, Johansson gauges, slip gauges, or Jo blocks) are a system for producing precision lengths.
The individual gauge block is a metal or ceramic block that has been precision ground and lapped to a specific thickness.
An important feature of gauge blocks is that they can be joined together with very little dimensional uncertainty,
which means that several blocks can be stacked to create a desired length, for example, 7 mm + 10 mm = 17 mm.
The blocks are joined simply by rubbing them against each other, which causes them to cling together (see "wringing").
Consequently, a small number of gauge blocks can be used to create accurate lengths within a wide range.
By using 3 blocks from a set of 30 blocks, one may create any of the 1000 lengths from 3.000 to 3.999 mm in 0.001 mm steps
(or .3000 to .3999 inches in 0.0001 inch steps). Gauge blocks were invented in 1896 by Swedish machinist Carl Edvard Johansson.[1]
They are used as a reference for the calibration of measuring equipment used in machine shops, such as micrometers, sine bars, calipers,
and dial indicators (when used in an inspection role). Gauge blocks are the main means of length standardization used by industry.

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Gages: Block, Pin, Plug, Thread

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