GAUGES
A gauge is an inspection tool that is used by engineers to measure the tolerance limit of a
component.
Classification Of Gauges
PLUG GUAGE
PLUG GUAGE
Plug gauges
Tools whose purpose is to check theinside diameters of holes that have been drilled or
machined into a manufactured part. It is a cylindrical shaped Go and Not- Go type Gauge.
In order to measure the parts it has to pass a measurement and another one has not to pass the
measurement. That is called Go and Not-Go measurement.
They are available in a variety of different tolerance classes which can be selected to suit the
specific needs of the application and the need for precision.
Snap Gauge
A snap gauge is a measurement tool used to check the outside dimensions of a part or material,
such as its diameter, length, or thickness
The Snap Gauge is the gauge which is U-shaped Go and Not-Go type gauge.
It has jaws by which it checks the accuracy and tolerance.
In order to measure the parts, it has to pass a measurement and another one has not to pass the
measurement.
Go is a high or maximum limit and the Not-Go is the low or minimum limit.
Snap Gauge
Ring Gauge
The Ring Gauge is the same as the snap gauge but it is separated the Go and Not-Go pass or in a
single ring.
Taylor’s Principle of Gauge Design
Statement 1
1. GO gauges should be designed to check the maximum material limit, while NO-GO
gauges should be designed to check the minimum material limit.
2. GO gauges should check all the related dimensions(Roundness, size etc.) whereas
NO-GO gauges should check only one dimension at a time.
Statement 2
The “Go” gauge should always be so designed that it will cover as many
dimensions as possible in a single operation, whereas the “NOT-GO”
gauge will cover only one dimension.
• If a short length Go-plug gauge is employed to check the curved bush, it will pass through
all the curves of the bend busing.
• This will lead to wrong selection of curved bush.
• GO-plug gauge of adequate length will not pass through a bent or curved bush.
• This eliminates the wrong selection.
• The length of NOT-GO gauge is kept smaller than GO- gauge.
Gauge Tolerance
• In practice, gauges cannot be manufactured to its exact dimensions.
• Some variation in sizes will be due to imperfections in process, skill of the worker etc.
• Therefore some tolerance is given to the gauge manufacturer for manufacturing of
gauges.
• Gauge Tolerance = 10 % of Work Tolerance
• For example, if the work tolerance is 100 units, then the manufacturing gauge
tolerance will become 10 units.
Wear Allowance
• Gauges rub constantly during working.
• Wear is inevitable.
• Wear allowance is provided.
• Wear Allowance = 50% of guage tolerance.
GAUGE MATERIALS
• The material used for manufacturing the gauges must be fulfill the following requirement
• Hardness to resist wear
• Stability of size and shape
• Corrosion resistance
• Machinability
• Low coefficient of thermal expansion
• Lower thermal conductivity
COMMONLY USED MATERIALS
• High carbon steel, which is relatively inexpensive and possess hardness and good stability.
• Steels plated with tungsten carbide, chromium, invar etc.
