Mechanical Measuring Tools

Different Types of Mechanical Measuring Tools:-
Measuring instruments and gauges are used to measure various parameters such as clearance, diameter, depth, ovality, trueness etc. These are important engineering parameters which describes the condition of the working machinery.







Popular mechanical gauges and tools used are:

1. Ruler and scales :
They are used to measure lengths and other geometrical parameters. They can besingle steel plate or flexible tape type tool.

2. Callipers :
They are normally of two types- inside and outside calliper. They are used to measure internal and external size (for e.g. diameter) of an object. It requires external scale to compare the measured value. Some callipers are provided with measuring scale. Other types are odd leg and divider calliper.

3. Venire calliper :
It is a precision toolused to measure a small distance with high accuracy. It has got two different jaws to measure outside and inside dimension of an object.It can be a scale, dial or digital type venire calliper.

4. Micrometer :
It is a fine precision tool which is used to measure small distances and is more accurate than the venire calliper. Another type is a large micrometer calliper which is used to measure large outside diameter or distance.

5. Feeler gauge :
Feelers gauges are a bunch of fine thickened steel strips with marked thickness which are used to measure gap width or clearance between surface and bearings.

6. Telescopic feeler gauge :
It is also known as tongue gauge and it consists of long feeler gauge inside acover with tongue or curved edge. The long feeler strips protrude out ofthe cover so that it can be inserted into remote places where feeler gauge access is not possible.

7. Poker gauge :
This gauge is used to measure propeller stern shaft clearance, also known as propeller wear down.

8. Bridge gauge :
Bridge gauges are used to measure the amount of wearof Main engine bearing. Normally theupper bearing keep is removed and clearance is measured with respect to journal. Feeler gauge can be used to complete the process.

9. Liner measurement tool :
Liner measurement tool is a set of straightassembled rod with marked length in each set. It is used to measure the wear down or increase in the diameter of the engine liner.

10. American Wire Gauge :
American wire gauge or AWG is a standard tool which is circular in shape and has various slots of different diameter in its circumference. It is used to measure cross section of an electric cable or wire.

11. Bore Gauge:
A tool to accurately measure size of any hole is known asbore gauge, It can be a scale, dial or digital type instrument .

12. Depth gauge:
A depth gauge is used to measure the depth of a slot, hole or any other surface of an object. It can be of scale, dial or digital type.

13. Angle plate or tool :
It is a right angle plate or tool used to measure the true right angle of two objects joined together.

14. Flat plate :
Flat plate is a precised flat surface used to measure flatness of an object when it is kept over the flat plate.

15. Dial Gauge :
Dial gauge is utilised in different tools as stated above and can be separately used to measure the trueness of the circular object, jumping of an object etc.

16. Lead Wire :
It is a conventional method to used soft lead wire or lead balls to measure the wear downor clearance between two mating surfaces. The lead wire or balls of fixed dimension is kept between two surfaces and both are tightened against each just as in normal condition. The increase in the width of the lead wire or ball will shoe the clearance or wear down.

Vocabulary Term	Definition
Accumulated Error	The collected inaccuracy in measurement that can occur when multiple elements are combined.
Accuracy	The difference between a measurement reading and the true value of that measurement.
Air Gage	A variable, non-contact pneumatic instrument that uses pressurized air to inspect the ID of holes.
Air Regulator	The part of a pneumatic inspection system by which pressurized air is controlled.
Backflow Pressure	Movement of pressurized air in the direction opposite to which it was pushed out of the device. In an air gage, backflow pressure is caused by resistance from the sides of the hole.
Bore Gage	A hole inspection gage that makes three points of contact within the hole. Bore gages are handheld, mechanical or electronic contact instruments with variable measuring systems.
Borescope	A non-contact optical inspection device consisting of a rigid or flexible tube with an eyepiece at one end and a magnifying lens at the other. Borescopes provide a view of hole interiors that are otherwise difficult or impossible to see.
Caliper	A handheld, variable contact instrument that functions as a precision slide ruler. The indicators on the top of the instrument expand to measure internal diameters.
Capable	A gage's predictable range of ability, even when under the influence of natural variation due to common causes.
Comparison Device	A measuring instrument that adjusts to assume the size of a feature.
Concavity	A curved surface condition like the inside of a ball.
Contact Instrument	A measuring device that actually touches the part in order to obtain its measured value.
Contact Probe	The main measuring member on a coordinate measuring machine that communicates its position on a workpiece to the CMMs control panel or computer. A probe often has a sphere of ruby at its tip.
Continuous Scanning	An inspection method used by a coordinate measuring machine in which the probe slides along the surface of the workpiece to collect seamless data in the form of a series of numerous points.
Coordinate Measuring Machine	A sophisticated electronic measuring instrument with a flat polished table that inspects parts in three-dimensional space using either a contact or a non-contact probe. All CMMs are variable devices.
Dial Indicator	A measuring instrument with a contact point attached to a spindle and gears that move a pointer on the dial. Dial indicators have graduations that allow you to read different measurement values.
Digital Readout	An indicator on a measuring device that presents data through a numerical display.
Electronic Instruments	Inspection devices that use electrical impulses to report either position changes or contact between the inspection device and the part.
Extension	A piece that is added to the head of an inside micrometer to expand it to the width of the hole.
Eyepiece	The part of a boroscope through which the inspector views the interior of the workpiece.
Flowmeter Tube	A cylindrical indicating device on a pneumatic measuring instrument that looks similar to a thermometer.
Gaging Instrument	An inspection device of a standard size that determines fit but does not determine actual measurement value.
Go-No Go Gage	An instrument that determines whether a part feature simply passes or fails inspection. No effort is made to determine the exact degree of error.
Indicator	A device, often numerical, that displays a measurement. An indicator may be a dial with a needle or a digital readout.
Inner Diameter	ID. The interior surface of a hole in a workpiece.
Inside Micrometer	A mechanical or electronic, variable, handheld contact instrument, usually cylindrically shaped, used to measure the inside diameter of larger holes.
Laser System	A non-contact, variable, optical inspection method that uses light to examine the inside diameter of holes. Laser systems send out a single light wave on a straight line that is detected by sensors and converted into an electrical signal.
Light Wave	A form of visible energy used by lasers.
Linear Scale	A series of parallel lines that represent a measurement standard. A ruler contains a linear scale.
Linearity	The amount of error change throughout an instrument's measurement range. Linearity is also the amount of deviation from an instrument's ideal straight-line performance.
Lobing	A condition in which the manufacturing process creates a rounded projection out from what would otherwise be a circular hole. A hole may have more than one lobe.
Master Gage	A measuring device of a standard size that is used to calibrate other measuring instruments.
Mechanical Device	A measuring instrument that must be physically manipulated by the inspector. Mechanical devices may be go-no go or variable.
Micrometer Head	The main component of an inside micrometer that includes the scale and indicating device. Extensions are added to the micrometer head.
Non-Contact Instrument	A measuring device that is able to obtain the measured value of the part without making physical contact. An air gage is an example of a non-contact instrument.
Optical Comparator	A sophisticated measuring instrument that projects an image of a part onto a screen to compare the shape, size, and location of its features. Optical comparators are non-contact, variable, optical inspection devices.
Optical Instruments	Inspection devices that use light and lenses to inspect parts. The part may be viewed directly through the lense or displayed on a screen.
Outside Micrometer	A handheld device consisting of an anvil, a shaft, and an indicator that is used to measure outside diameters.
Ovality	A condition in which a hole that should be round has two opposing lobes, resulting in an egg shape.
Pin Gage	A cylindrically shaped length of metal of a specific diameter used as a gaging inspection device. A pin gage is a handheld mechanical contact instrument.
Plug Gage	A hardened, cylindrical gage used as a handheld mechanical contact instrument to inspect the size of a hole. Plug gages are available in standard diameters and are often two-sided, with a "go" side and a "no go" side.
Pneumatic Instrument	A measuring device that uses a pressurized gas, such as air, to function.
Precision	The degree to which an instrument will repeat the same measurement over a period of time.
Probe Cable	The portion of a laser system that transmits information and power to and from the tip of the device and the computer.
Ring Gage	A circular measuring device of a standard size that is used to calibrate other instruments or inspect cylindrical parts.
Rotary Laser	An inspection device that projects a light wave on the surface of the part's internal diameter as it turns.
Scale	A standard of measurement that is often displayed as a series of lines.
Setting Gage	A measuring device of a standard size that is used to check or prepare a working gage for use. Bore gages often come with matching setting ring gages.
Split-Ball Gage	A cylindrical device with an expanding, flat-ended ball on one end and a locking device on the other. A split-ball gage is a handheld, mechanical contact instrument that is used for comparison measurement. It is also called a small-hole gage.
Taper	A gradual narrowing of an inside or outside surface.
Telescoping Gage	A T-shaped measuring device that has two spring-loaded measuring arms and a lock in the base. A telescoping gage is a handheld, mechanical contact instrument used for comparison measurement.
Thimble	A ring or cylinder that fits around the spindle of a micrometer. To advance the spindle, you turn the thimble.
Tolerance	The acceptable variation from a specified dimension.
Tolerance Range	The expected range of measurements produced by a given operation. It is also known as a tolerance zone.
Variable Instrument	An inspection device calibrated in standard measurement units. Variable inspection reveals the degree of variation from a given standard.
Video Borescope	A borescope that contains a video camera rather than an eyepiece.
Working Gage	A measuring device of a standard size that is used to inspect parts.