CONTENTS

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1.0 Title 2

2.0 Objective 2

3.0 Introduction 2

4.0 Apparatus 6

4.1 Industrial Apparatus 7

5.0 Experimental Procedure 8

6.0 Results and Data Analysis 9

7.0 Discussion of Results 12

8.0 Conclusion 14

9.0 Recommendation 15

10.0 References 16

1.0 TITLE : SCREW THREAD MEASUREMENT

2.0 OBJECTIVE

To measure the Major Diameter, Minor Diameter and the Effect Diameter of a Screw Plug

Gauge using Floating Carriage Measuring Machine.

3.0 INTRODUCTION

Floating Carriage Diameter is also commonly known as Effective Diameter Measuring

Micrometer. It use Bench micrometer to hold the workpiece as they look like they are

floating. This instrument is used for accurate measurement of Screw Plug Gauges

dimension such as Major Diameter, Minor Diameter and Effective Diameter. All these

dimensions such as Major Diameter, Minor Diameter and Effective Diameter. All these

dimensions have an important role in the screw plug gauges, since the accurancy and

interchangeability of the component depends on the gauges used. To minimize the effect

of slight errors in the micrometer screws and measuring faces, this micrometer is

fundamentally used as comparator.

Figure 2 : Thread Terminology

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a) Major Diameter : This is the diameter of an imaginary cylinder, co-axial with the screw,

which just touches the crests of an external thread or roots of internal threads. Also

known as Nominal diameter.

Referring to the Figure 3.0

If the micrometer reading over Standard Cylinder = R1

The micrometer reading over Screw Pug Gauge = R2

The diameter of Standard Cylinder = D1

Therefore, Major Diameter of Screw Plug Gauge, Dmajor= D1+(R1+R2)

Figure 3.0 : Screw Terminology

b) Minor Dimension : This is the diameter of an imaginary cylinder, co-axial with screw

which just touches the roots of an external thread. Also referred as root or core

diameter.

Referring to the figure 3.1

If the micometer reading over Standard Cylinder and Core Prisms = R3

The micrometer reading over Screw Pug Gauge and Core Prisms = R4

The diameter of Standard Cylinder = D1

Therefore, Minor Diameter of Screw Plug Gauge, Dminor= D1+(R3+R4)

Figure 3.1

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c) Effective diameter : Also known as Pitch Diameter. It is the Diameter of imaginary

Cylinder,co-axial with the axis of the thread and intersects the flank of the thread and

intersects the flanks of the thread such that width of the threads and width of spaces

between threads are equal.

Referring to the Figure 3

If the micometer reading over Standard Cylinder and Wires = R5

The micrometer reading over Screw Pug Gauge and Wires = R6

The diameter of Standard Cylinder = D1

Therefore, the Diameter with the wire D3= D1+(R5+R6)

Hence, the Effective Diameter, Deff = D3+P where P is the difference between Effective

Diameter and the diameter under the wires as shown in Figure 4

The P calue is a constant depending on the diameter of the wires (d), the pitch (p) and the

type of screw thread, it is found as follows:

Metric Threads (60°) P = 0.86602p –d

Whitworth threads (55°) P = 0.9604p – 1.16568d

British Association Threads (47.5°) P = 1.13634p – 1.43295d

Note : Pitch, p given is 3.5mm

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4.0 APPARATUS

1. A Floating Carriage Diameter Measuring Machine

2. A Set of Core Prism

3. A Set of Calibrated Screw Thread Measuring Wires (Wire Cylinders)

4. A Set of Metric Cylindrical Standards

5. Screw Plug Diameter

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4.1 INDUSTRIAL APPARATUS

1. Micrometer Screw Gauge

2. Vtd Image Processing Measuring Device for Internal Screw Thread Measurement

3. Tool Maker Microscope

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5.0 EXPERIMENTAL PROCEDURE

Major diameter

1. The position of the fiducial indicator and the micrometer anvil and the gauge to

be measure is between or within the range of the micrometer.

2. A suitable Standard Cylinder was placed between the center the Standard

Cylinder should have diameter within 1mm of the actiual major diameter of

workpieace. The micrometer deum reading R1 is been noted

3. The standard was removed and was replaced with the Screw Plug Gauge to be

measured. The micrometer drum R2 is been taken.

4. The major diameter, Dmajorwas evaluated

Minor diameter

1. The position of the fiducial indicator and the micrometer anvil and the gauge to

be measure is between or within the range of the micrometer.

2. A suitable Standard Cylinder was placed between the center. The selected

prism was been inserted between the standard and the anvils. The hanging

prism should be vertical. The reading on micrometer drum R3 was taken.

3. The standard was removed and was replaced with the Screw Plug Gauge to be

measured. The prism was inserted between the thread grooves and the anvils

and the micrometer reading R4 was taken.

4. The Minor Diameter, Dminorwas evaluated

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Effective Diameter

1. A suitable Standard Cylinder was placed between the center. The Standard

Cylinder should have diameter within 1mm of the actual diameter of

workpiece.

2. The wires selected were inserted in position between Standard Cylinder and

micrometer anvils. The wires were selected accordance N.P.L

recommendation. The reading on micrometer drum R3 was taken.

3. The Standard Cylinder was replaced with Screw Plug Gauge. Note the

micrometer reading R2 with the wre inserted in the thread grooves.

4. The Effectice Diameter, Deff was evaluated.

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6.0 RESULTS AND DATA ANALYSIS

Micrometer

reading

over

standard

cylinder,R1

(mm)

Micromete

r reading

over screw

plug

gauge , R2

(mm)

Micrometer

reading

over

standard

cylinder

and core

prisms, R3

(mm)

Micromete

r reading

over tread

and core

prisms, R4

(mm)

Micrometer

reading

over

standard

cylinder

and wire,

R5 (mm)

Micrometer

reading

over screw

thread and

wire, R6

(mm)

sleve 3.5 3.5 10.5 7.5 7.5 4.5

Thimble 0.47 0.35 0.12 0.04 0.46 0.18

Sub

Thimble

0.002 0.002 0.000 0.006 0.004 0.002

Sub Sleve 0.0016 0.0010 0.0002 0.0010 0.0020 0.0014

Total 3.9756 3.8530 10.6202 7.5470 7.9660 4.6832

Sample calculation

To determine R1

= Sleve + Thimbe + Sub-Thimble + Sub-Sleve

= 3.5 + 0.47 + 0.004 + 0.0016

=3.9756

*Repeat the same calculation method to find R2, R3, R4,R5,R6

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Major Diameter Of Screw Plug Gauge

Where D1 is diameter of standard cylinder = 30mm

Dmajor = D1 + (R2 - R1 )

= 30 + (3.8530 – 3.9756)

= 29.8774 mm

Minor Diameter Of Screw Plug Gauge

Dminor = D1 + (R4 – R3 )

= 30 + (7.5470 – 10.6202 )

= 26.9268 mm

Effective Diameter

Diameter under the wire, D3

D3 = D1 + (R6 – R5 ).

= 30 + (4.6832 – 7.9660 )

= 26.7172 mm

Metric Threads (60o), P = 0.86602p – d

Where is p = 3.5 mm and d = 2.083 mm

P = 0.86602(3.5) – (2.083)

= 0.9481 mm

Therefore,

Deff = D3 + P

= 26.7172 + 0.9481

= 27.6653 mm

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Comparison between theoritical value and experiment value

Theoritical Value ( mm ) Experimental Value (mm)

Major Diameter 30.000 29.8774

Minor Diameter 26.211 26.9268

Effective Diameter 27.727 27.6653

Percentage Error =

Experimental−TheoriticalTheoritical

Major Diameter Percentage Error =

29.8774−30.00030.000

Minor Diameter Percentage Error =

26.9268−26.21126.211

= 2.73 %

Effective Diameter Percentage Error =

27.6653−27.72727.727

= 0.22%

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7.0 DISCUSSION OF RESULTS

Based on the experiment, the geometrical parameter of the specimen, which is screw

plug gauge, was measured by using profile projector to check the profile. The screw plug

gauge parameters that are needed to measure are major diameter, minor diameter and

effective diameter. From the specimen, the dimension of ISO metric thread and identification

of threads can be known. For instant, M30-3.5-ISO 6H where M is metric standard thread

angle 60°, 30 is major diameter (mm), 3.5 is pitch of thread (P) and ISO 6H is matrix standard

table (tolerance).

During the experiment, the major diameters have been measured three times and the

average major diameter can be calculated. The average diameter is 29.959 mm and the actual

major diameter is 30.00 mm. The experimental major diameter varies slightly from the actual

major diameter. The percentage error can be calculated which is 24.83%. The average minor

diameters have been measured and calculated which is 24.89 mm but the actual minor

diameter is 25 mm. By comparing the actual minor diameter and the measured diameter the

percentage error is 19.94%. The effective diameter has been measured which is 27.67 mm

whereas the actual effective diameter is 27.5 mm.

There are many possibility ways that errors might occur in readings for each time the

readings are taken. There may occur due to miss alignment of the specimen since there is no

fix location to set the specimen in a correct coordinate. Other possible errors are parallax error

which occurred when eyes positioning is misplaced during setting the alignment. The error

also may be involved due to the system error where apparatus or machine is not well

calibrated. Besides, students’ familiarity towards the machine may affect the error where

students may not handle properly during the experiment.

Other than that, for the result obtained from the coins, we found 0.178mm diameter

marbles in each hole of the congkak on the 10 cents coin. As we counted all the marbles, the

total marbles that can be found on the 10 cents coin are 45. For the new 20 cents coin, we

found the B,N and M letter between the big flower and small flower. Other than that, for the

new 50 cents we also found the B,N and M letter at the floral design.

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There are necessary precautions which must be implementing to minimize the error

during the experiment. Students need to know how to handle properly throughout the

experiment and full attention must be given when conducting the experiment.

1. The surface of the specimen is needed to be clean from all contaminant such as oil,

dust, moisture and many more to ensure the accurateness of each reading. 

2. The specimen must be placed at the correct position where the projector can show the

image clearly so that readings can be taken correctly.

3. Eyes level must be placed perpendicular to the readings to avoid parallax error.

8.0 CONCLUSION

In a nutshell, we can conclude that the experiment is successfully conducted as we has

fulfill the objective of the experiment which is to check the profile and measure the

geometrical parameters of the given specimen (screw thread) by using profile projector.

For the coins experiment, the purpose of the result obtained from the coins is for the

national security so that people cannot duplicate our coins from our country easily.

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From the profile projector, major diameter, minor diameter and effective diameter of

the specimen can be determined. By comparing between the experimental data and actual

data, the value that we obtained was closed to the standard value. Hence, we consider the

experiment is successful as the percentage errors are more likely below than one percent.

9.0 RECOMMENDATION

1. Other optical system than using profile projector is Coordinate Measuring Machine

(CMM) where the measurement data taken from CMM is more precise and less error

contribute to the experiment. The measurements are more likely defined by a probe

attached to the third moving axis. This machine can be manually controlled or it may

computer controlled.

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2. It is recommended for the profile projector to have a high resolution and a more

focusing lens to have a sharp view on the screw thread so that when alignment is being

adjusted, there would be no flaw or error exists throughout the experiment.

3. Before given to the students, it would be recommended if the technician could check

the screw plug gauge quality if any defects could detect prior to experiment. Thus, it

can minimize the errors.

10.0 REFERENCES

1. Serope Kalpakjian & Steven R. Schmid, Manufacturing Processes for Engineering

Materials, 4th Edition, Illinois Institute Of Technology, Prentice Hall, 2003.

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2. Serope Kalpakjian, W.R. Schmid, Manufacturing Technology and Fundamental, 5th

edition, Prentice Hall, 2004.

3.  http://www.engineersedge.com/screw_threads_chart.htm

4. http://www.threadcheck.com/the-three-wire-method-of-measuring-pitch-diameter/

technicalinfo/

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