CLD 20502 BASIC ENGINEERING WORKSHOP

Topic 2Basic Hand/ Workshop/ Measurement Tool and Their Uses

Introduction

objective

To understand the theory of metrology.

To identify and used measurement tool, marking, hand, workshop tool.

To use and practice measurement on mechanical component and to ensure the product is in the range of the specification required.

Measurement

Dimension Surface Measurement unit Dimensional metrology Geometric attribute Measurement tool – linear and

angular

Measurement Dimension Dimensions are the linear or angular sizes

of a component specified on the part drawing.

Dimension includes width, depth, length, thickness, diameter value that define the sizes of a part.

It is important as they determine how well the components of a product fit together during assembly.

System of measurement consists of English system (in-lb-sec) and metric system (m-kg-sec).

Measurement

Tolerance A tolerance is the total amount by which

a specific dimension is permitted to vary. The tolerance is the difference between the maximum and minimum limits.

Measurement Dimensional metrology

Precision - Relative to specific measurement being made with regard to the degree of exactness required.

Accuracy - Whether or not a specific measurement is actually within its stated size.

Reliability - Ability to obtain the desired result to the degree of precision required.

Discrimination - Degree to which a measuring instruments divides the basic unit of length it is using for measurement.

Calibration - Consistency of measuring tools to the appropriate standards.

Question 1

How you define the following?

Measurement

Geometric attribute

Measurement

Geometric attribute

Measurement

Surface Measurement and inspection of surface

condition is important because ; Aesthetic reason – smooth and free from scratches

and blemishes is preferred by customer Surfaces affect safety Friction and wear depends on surface

characteristics It affect mechanical and physical properties Assembly method required smooth and clean

surface. Electrical contacts is better in smooth surface.

Measurement

Surface texture features

Measurement Tool

Linear measurement Caliper Ruler Vernier caliper Micrometer

Angular measurement Protractor Combination set

Linear measurement

Linear measurement

Caliper A nongraduated caliper consists of two legs

joined by a hinge mechanism. The ends of the legs are made to contact the

surfaces of the object being measured and the hinge is used to hold the leg position.

Outside caliper is use to measure outside dimension such as a diameter. The leg is point inward.

Inside caliper is use to measure inside dimension such as a distance between internal surface. The leg is point outward.

Linear measurement

Caliper

Linear measurement

Ruler and tape rule Ruler is a line

measuring instrument used for direct measurement. It is also used as a divided instrument.

Common lengths are 150 mm (6 in.) and 300 mm (12 in.)

Linear measurement

Ruler and tape rule A tape rule is a steel

blade coiled inside a carrying case.

It provides and easy means for accurately measuring curved surfaces because it is flexible.

Linear measurement

Vernier caliper A beam with a jaw at

right angles and movable jaw which slides along the beam.

It is used to measure inside, outside and depth measurement of any object.

It come with varies accuracy; 0.1, 0.02, 0.05 mm.

Linear measurement

Vernier caliper

Read a vernier caliper

Read the main/ metric scale 28.00 mmRead the vernier scale 0.48 mmTotal reading 28.48 mm

Question 2

Linear measurement

Micrometer A very accurate measuring device

closed to 0.01 mm or 0.001 in. It can be use to measure external

dimension and outside surface such as a thickness of sheet metal and diameter of drills.

Linear measurement

Micrometer The most common form consists of a spindle

and a C-shaped anvil. Shown here is the outside micrometer.

Read a micrometer

Micrometer

Question 3

Angular measurement

Protractor & Combination set Angular measuring instrument. Used for layout and checking the

point angle of drill, taper on lathe machine center and along the tapers.

Angular measurement

Combination set

Angular measurement

Combination set

History

The Great Kersten Blunder (Kersten was the programmer that made the error). The vigor space probe was sent towards Venus but because of a computer programming error installed on it, a conversion from mm to inch was incorrect. It divided by 24.5 instead of 25.4.

This error caused it to miss Venus completely and was sent hurling into space. Over 2 billion dollars of technology was lost because of one simple error.