WORKSHOP PRACTICE

LAB No. 2

Measuring Tools

Today’s LAB

Measuring Tools Vernier Caliper Micrometer SWG

Measurement

Measurement means to compare something with standard.

E.g. measuring length of a wire, diameter of a cylinder, depth of any object.

The SI unit of length is meter (base unit). Its multiples and sub-multiples are given in

the table.

Meter and its sub-multiples

Prefix SymbolRelationship with Meter (base unit)

meter m 1m = 1 m

deci dm 1dm = 10-1 m

centi cm 1cm = 10-2 m

milli mm 1mm = 10-3 m

micro µm 1 µm = 10-6 m

nano nm 1nm = 10-9 m

pico pm 1pm = 10-12 m

Meter and its multiples

Prefix SymbolRelationship with

meter

deca da 1 dam = 101 m

hecto h 1 hm = 102 m

kilo k 1 km = 103 m

mega M 1 Mm = 106 m

giga G 1 Gm = 109 m

Measuring Tools

Vernier caliper Vernier caliper is a measuring device used to measure

precise increments between two points.

Micrometer Micrometer is a measuring device used for precisely

measuring thickness, inner and outer diameter, depth of slots.

SWG A gauge for measuring the diameter of wire, usually

consisting of a long graduated plate with similar slots along its edge.

Vernier caliper

Function To measure smaller distances Can measure up to .001 inch or .01mm.

Features Larger, lower jaws are designed to measure outer points

e.g. diameter of a rod. Top jaws are designed to measure inside points e.g. size of

a hole. A rod extends from the rear of the caliper and can be used

to measure the depth.

Structure of Vernier caliper

Structure of the Vernier caliper

Main Scale Main scale is graduated in cm and mm.

Vernier Scale It slides on the main scale. On Vernier scale 0.9cm is divided into 10 equal parts.

Jaws Two inside jaws (Upper) Two outside jaws (Lower)

Least Count

Least count (L.C) is the smallest reading we can measure with the instrument.

L.C = one main scale division – one vernier scale divisionL.C = 1mm – 0.09mm

L.C = 0.1mm = 0.01cm

Least Count = Value of the smallest division on MS/ Total number of division on VSL.C = 1mm / 10 = 0.1 cm / 10 = 0.01cm

How to use Vernier caliper?

• Close the jaws• Calculate the least count• Place the object between

the two jaws• Record the position of zero

of Vernier scale on the Main scale (3.2cm)

• Notice the reading of VS which coincides with MS reading (3rd division in this case)

Reading of the Instrument

Reading of the instrument = MS div + (coinciding VS div x L.C)

= 3.2 + (3 x 0.01) = 3.2 + 0.03 = 3.23 cm

Sample Picture

To measure the depth

A rod extends from the rear of the caliper and can be used to measure the depth.

Open the jaws of caliper and place the rod inside hole of the object, such as the rod reaches the inner most portion of the object.

Read the Vernier caliper. (same procedure as described in previous slides)

Micrometer

Function Micrometer allows the measurement of the size of the body

i.e. thickness, depth, inner/outer diameter.

Features Two jaws (one fixed, one movable) Spring loaded twisting handle Easy to use and more précised Can measure up to .001cm

Structure of the Micrometer

Structure of Micrometer

Jaws 2 jaws (one fixed, one movable)

Circular Scale Movable jaw is attached to a screw, scale on this screw is

called Circular scale. Either 50 or 100 divisions

Linear Scale Horizontal Scale

Structure of Micrometer

Frame The C-shaped body that holds the anvil and sleeve in constant relation to

each other. Anvil

The jaw which remains stationary. Spindle

The jaw which moves towards the anvil. Lock Nut

A lever, one can tighten to hold the spindle stationary. Sleeve

The stationary round part with the linear scale on it. (Main Scale) Thimble

Thimble rotates around the sleeve. Ratchet Stop

Device on end of handle that limits applied pressure by slipping at a calibrated torque.

Pitch of Micrometer

When the head of the micrometer rotate through one rotation, called pitch of the micrometer.

The screw moves forward or backward 1mm on the linear scale.

Pitch of Micrometer = distance on linear scale / one rotation

Pitch of Micrometer = 1/1 = 1mm

Least Count

Least Count = Pitch of the Micrometer / Total number of circular scale division

Least Count = 1 / 100 = 0.01mm = 0.001cm

How to use Micrometer?• Thimble

– The thimble rotates around a cylinder which is marked in millimeters.

– The left-hand side of the thimble has markings all around it.

– The line labeled 0 is the primary pointer.

• Close the jaws• Calculate the least count• Place the object between the

two jaws• Record the position of main

scale where the two measuring rods met.

• Note the position of the circular scale which coincides with main scale

Reading of the Instrument

Reading of the instrument = MS div + (coinciding CS div x L.C)

= 8+ (12 x 0.01) = 8 + 0.120mm = 8.120 mm = 8120 µm

Standard Wire Gauge (SWG)

A gauge for measuring the diameter of wire, usually consisting of a disk having variously sized slots in its periphery or a long graduated plate with similar slots along its edge.

A standardized system of wire sizes. Wires are manufactured to standard sizes and

labeled with their SWG. As the SWG increases the diameter decreases.

SWG

SWG No. Diameter (inches) Diameter (mm)

0 0.324 8.230

1 0.300 7.620

2 0.276 7.010

3 0.252 6.401

4 0.232 5.893

5 0.212 5.385

Lab Reports

Last date of submission of Lab 1 & 2 is Wednesday, 4th November till 1: 00 p.m. in Workshop lab.