Center gauges and fishtail gauges are
gauges used in
lathe
A lathe () is a machine tool that rotates a workpiece about an axis of rotation to perform various operations such as cutting, sanding, knurling, drilling, deformation, facing, threading and turning, with tools that are applied to the w ...
work for checking the angles when grinding the profiles of
single-point screw-cutting tool bit
In machining, a tool bit is a non-rotary cutting tool used in metal lathes, shapers, and planers. Such cutters are also often referred to by the set-phrase name of single-point cutting tool, as distinguished from other cutting tools such as a s ...
s and
centers. In the image, the gauge on the left is called a fishtail gauge or center gauge, and the one on the right is another style of center gauge.
These gauges are most commonly used when hand-grinding threading
tool bit
In machining, a tool bit is a non-rotary cutting tool used in metal lathes, shapers, and planers. Such cutters are also often referred to by the set-phrase name of single-point cutting tool, as distinguished from other cutting tools such as a s ...
s on a
bench grinder
A bench grinder is a benchtop type of grinding machine used to drive abrasive wheels. A pedestal grinder is a similar or larger version of grinder that is mounted on a pedestal, which may be bolted to the floor or may sit on rubber feet. Thes ...
, although they may be used with
tool and cutter grinder
A Tool and Cutter Grinder is used to sharpen milling cutters and tool bits along with a host of other cutting tools.
It is an extremely versatile machine used to perform a variety of grinding operations: surface, cylindrical, or complex shapes. T ...
s. When the tool bit has been ground to the correct angle, they are then used to set the tool
perpendicular
In geometry, two geometric objects are perpendicular if they intersect at right angles, i.e. at an angle of 90 degrees or π/2 radians. The condition of perpendicularity may be represented graphically using the '' perpendicular symbol'', ⟠...
to the workpiece.
They can incorporate a range of sizes and types on the one gauge, the two most common being
metric
Metric or metrical may refer to:
Measuring
* Metric system, an internationally adopted decimal system of measurement
* An adjective indicating relation to measurement in general, or a noun describing a specific type of measurement
Mathematics
...
or
UNC and UNF at 60°, and
BSW BSW may refer to:
*Bachelor of Social Work, an academic qualification at some institutions
*Bally Sports West, American regional sports network owned and operated by Bally Sports
* Batesville Southwestern Railroad, Mississippi, United States
*Beth ...
at 55°. Gauges also exist for the
Acme thread form
Trapezoidal thread forms are screw thread profiles with trapezoidal outlines. They are the most common forms used for leadscrews (power screws). They offer high strength and ease of manufacture. They are typically found where large loads are re ...
.
References
Dimensional instruments
Metalworking measuring instruments
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