uploadfolder 3808 workshop practice

7/28/2019 Uploadfolder 3808 Workshop Practice

http://slidepdf.com/reader/full/uploadfolder-3808-workshop-practice 1/26

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 acylinder, 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 slotsalong 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 VSwhich 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 rotationPitch 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 inmillimeters.

– The left-hand side of thethimble has markings allaround it.

– The line labeled 0 is theprimary pointer.

• Close the jaws

• Calculate the least count

• Place the object between thetwo jaws

• Record the position of mainscale where the two measuringrods met.

• Note the position of the circular scale which coincides withmain 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.

uploadfolder 3808 workshop practice

Documents