To measure the diameter of the given set of pins by using Screw gauge.

Experiment No. 02

Objective:

To measure the diameter of the given set of pins by using Screw gauge.

Apparatus:

  i.            Screw gauge

ii.            Pins of different diameter

Figure 2.1: Micrometer

Theory:

A micrometer is a device incorporating a calibrated screw widely used for precise measurement of components.

Types of micrometer:

Each types of micrometer caliper can be fitted with specialization anvils and spindle tip for particular measuring tasks.

Universal Micrometer:

Universal micrometer sets come with interchangeable anvils, such as flat , spherical, spline, disk, blade, point and knife edge. The term universal micrometer may also be refer to a type of micrometer whose frame has modular components allowing one micrometer to function as out micrometer, depth micrometer, step micrometer.

Blade Micrometer:

Blade micrometer has a matching set of narrow tip.

Pitch diameter micrometer:

Pitch diameter micrometer have a matching set of thread shaped tip for measuring the pitch diameter of screw threads.

Limit micrometer:

Limit micrometer have two anvils and two spindles, and are used like a snap gauge, The part being checked must pass through the first gap and must stop at the second gapin order to within specification.

Digit Micrometer:

Digit micrometer is the type with mechanical digits that roll over.

Digital micrometer:

Digital micrometer is type that uses an encoder to detect the distance and displays the result on a digital screen.

Parts of micrometer:

Micrometer screw gauge is used to measure precisely. Parts of the screw gauge.

Frame:
The c shaped body that holds the anvil and barrel in constant relation to each other. It is thick because it needs to minimize flexion, expansion, and contration, which would distort the measurement.
Anvil:
The shiny part that the spindle moves toward, and that the sample rests against.
Sleeve:
The stationary round component with the linear scale on it, sometimes with Vernier marking. In some instruments the scale is marked on a tight fitting but movable cylindrical sleeve fitting over the internal fixed barrel. This allows zeroing to be done by slightly altering the position of sleeve.
Lock nut:
The knurled component (or lever) that one can tighten to hold the spindle stationary, such as when momentarily holding a measurement.
Screw:
The heart of the micrometer , as explained under “Operating principles”. It is inside the barrel.
Spindle:
The shiny cylindrical component that one’s thumb cause to move toward the anvil.
Thimble:
The component that one’s thumbs turns. Graduated marking.
Ratchet stop:
Device on the end of handle that limits applied pressure by slipping at a calibrated torque.

Figure 2.2: Components of Micrometer

Positive zero error:

If the zero of the head scale lies below the base line (B.L) of the pitch scale then the zero error is positive and zero correction is negative. The division on the head scale, which coincides with the base line of pitch scale, is noted. The division multiplied by the least count gives the value of the positive zero error. This error is to be subtracted fromthe observed reading i.e. the zero correction is negative

Negative zero error:

If the zero of head scale lies above the base line (B.L) of the pitch scale, then the zero error is negative and zero correction is positive. The division on the head scale which coincides on the base line of pitch scale is noted. This value is subtracted from the total head scale divisions. This division multiplied by the least count gives the value of the negative error. This error is to be added to the observed reading i.e. zero correction is positive

Procedure: 

Observation and Calculation:

Least Count:     0.001

Total reading-Main scale reading + circular scale reading × Least count

Dimension of Object	Sr No.	Main Scale Reading            (A)                     mm	Circular Scale Reading			Total Reading A+B          cm	Correction Reading D±C
			Concide marks  N		B=N×L.C    mm
Dia of Sphere	i.
	ii.
	iii.

Precautions: 

i.