lab 1: metrologyportal.unimap.edu.my/portal/page/portal30/lecture...

ENT 155/4 LAB 1: METROLOGY MANUFACTURING PROCESSES

School of Mechatronic Engineering

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LAB 1: METROLOGY

1. OBJECTIVE 1.1 To familiarize students with measuring techniques and the use of standard measuring

instruments 1.2 To practice measuring sample parts and to solve all given problems 1.3 To impress students that the degree of accuracy and procession depends upon the

skill and ability of the persons as well as upon the instruments 2. INTRODUCTION

2.1 VERNIER CALIPER

Vernier caliper is a common measuring instrument which is widely used in workshop. It is made up of graduated beam with a fixed measuring jaw and a movable jaw which carries a vernier scale. As shown in figure 1, vernier caliper is capable of making both outside and inside measurements. Some are also provided with a depth measuring rod to measure the depth of work piece.

Figure 1: Parts of Vernier Caliper

Application of vernier calliper:-

• External measurement : e.g. measuring length of the workpiece • Internal measurement : e.g. measuring size of the hole • Depth measurement : e.g. measuring depth of the slot or hole



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Figure 2: The Vernier Caliper

Figure 3: Measuring (A) inside and (B) outside diameters with a dial/vernier 2.1.1 Procedure

• There is a fixed scale and sliding scale

• There are ten tick marks on the sliding scale and nine tick marks on the fixed scale. In figure 2 the sliding scale is between 21 mm and 22 mm, so the number of whole millimeters is 21.



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Figure 4: Reading Accuracy at fixed scale and sliding scale

• The 3rd tick mark on the sliding scale is in coincidence with the one above it, so the caliper reading is (21.30 ± 0.05) mm.

• If the 3rd and 4th tick marks on the sliding scale looked to be equally aligned, then the reading would be (21.35 ± 0.05)

2.1.2 Reading the Measurement Value

Figure 5: Vernier Measurement Value

From figure 5, the point 0 on the vernier shows us that the distance measured is more than 7.0 mm. Reading the graduation on the vernier which is coincides exactly with the main scale is 0.6 mm. Measuring result = 7.0 + 0.6 mm = 7.6 mm 2.1.3 Guidelines for Measuring

• The measuring surfaces should be clean and free from burrs • Open the measuring jaw clear of the workpiece, then slide it forward to make

measuring contact • Use gentle pressure when measuring • Do not pull the set vernier calipers over the workpiece unnecessarily when the slide is

screwed tight • When taking a reading, make sure your viewpoint is vertical to the scale • Before you lift the calipers off the workpiece, release the slide, otherwise the

measuring surfaces will get worn • Avoid heating up the instrument thorough the heat of your hands • Check vernier caliper for accuracy at frequent intervals. Measurement accuracy can

be tested with gauge block (calibration)



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2.2 MICROMETER

The micrometer can be used to make a variety of accurate measurement without the possibility of error through misreading which exists when other finely graduated tools are used. A micrometer combined the double contact of the vernier caliper with a precision screw adjustment.

The one inch micrometer consists on 3 main parts:- 1. the spindle 2. the sleeve 3. the thimble

When turned, a screw thread that attaches the spindle to the sleeve, advances the thimble one-fortieth (.025”) of an inch with each complete rotation. The screw thread on the spindle are concealed by the sleeve, which is marked longitudinally by forty lines, each division is .025”. Every fourth line is longer than the rest, indicating tenth of an inch. The edge of the thimble is marked with twenty five numbered divisions around it’s circumference.

Figure 6: Parts of Micrometer



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2.2.1 Procedure

• Place the object in between the spindle and the anvil and tighten it by turning thimble on the end.

• Determine how many tenths of an inch the edge of the thimble is from the zero mark on the sleeve. In figure 7, on the edge of the thimble is past the two-tenths mark.

• Each of the non-numbered sleeve graduation represents .025”. In figure 7, the edge of the thimble has not even reached .025” past the two-tenths mark.

• Observe the nearest graduated line, the number on the thimble which is most closely aligned with the horizontal axis line on the sleeve. In figure 7, on the next page, the closest marked line on the thimble to the axis line is 14.

• Add .200” and .014” to obtain an accurate measurement of the object depicted in figure 2.

Figure 7: One Inch Micrometer Caliper Reading

2.2.2 Reading the Measurement Value Measurement value: Sleeve - 8 upper graduations = 8.00 mm Interpolation - = 0.005 mm Thimble - 11th graduation = 0.110 mm



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Figure 8: Micrometer Measurement Value 2.2.3 Guidelines for Measuring

• Measuring surfaces should be clean and free from burrs • Advance the spindle gradually towards the workpiece • Applied measuring pressure limited to 10N, between workpiece and measuring

spindle • Used ratchet to avoid excessive pressure when rotating the spindle • Check micrometer for accuracy at frequent interval by using gauge block (calibrate)

2.3 PROTRACTOR

Angles are checked by using measuring instruments such as :-

1. simple protractor 2. universal bevel protractor

These are display instruments for direct measuring of any angle within a given measuring range.

For simple protractor, the pointer like arm can be set against a circular degree scale from 0° to 180° (measuring range). Only whole degrees can be measured using this protractor. Intermediate values can only be estimated. The measuring accuracy is 1 degree.



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Figure 9: The Simple Protractor

Figure 10: Simple protractor reading Universal Bevel Protractor makes it possible to measure any angle with reading accuracy of 5 minutes. It consists of fixed and movable measuring edge. The circular main scale is divided into 4 sections of 90° and serves to read the complete angular degrees. The angle nonius (vernier) consists of arc of 23°, divided into 12 equal intervals.



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Figure 11: The Universal Bevel protractor Figure 12: When reading from 90 degrees, make sure to note the positions where the angle and the supple- ment are formed Figure 13: Bevel Protractor reading



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2.3.1 Procedure

• Whole degree is the main scale with the zero markers on the vernier scale. • To get the minute values, read off which graduated marking on the vernier scale is

positioned next to a graduation on the main scale. • This value added tot the whole degrees to obtain the complete reading.

2.3.2 Reading the Measurement Value The graduation of the vernier from 0 to 60 represents 23° exactly and is divided into 12 equal parts. This means the distance between graduated marks is 23/12° = 1° 55′ the difference at 2° produces a reading accuracy of 5′.

Figure 14: Angle vernier reading value For universal protractor, depending upon the setting. One counts the full degrees from 0° to 90° up to the zero mark of the nonius (angle vernier). Then, one proceeds along the same direction on the nonius scale to the point where a mark on the main scale coincides with a mark on the nonius scale. This tells us how many units of 5′ have to be added to the number of full degrees.

Figure 15: Universal Protractor reading value



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Figure 16: Some of the examples protractor reading value



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2.4 GAUGE BLOCKS (SLIP GAUGES)

Parallel gauge blocks embody measure in the distance between two plane parallel surfaces. They are the most accurate form of representing size when measuring the length. They are usually come in three standard shapes: round, square and rectangular. They are made of hardened tool with plane parallel measuring surfaces. These measuring surfaces are well finished by lapping.

Figure 17: A standard set of gauge blocks

Gauge blocks are hardened very carefully up to a Rockwell hardness of HRC 65-67 and very resistant to wear. The measuring surfaces of the gauge blocks are so smooth and even, that clean locks may be attached together by wringing method to obtain the length required for measurement. They may be drawn apart or pushed together with very little pressure.

Figure 18: Wringing gauge blocks together Gauge block come in set and arranged in graduated steps and presented in rows. Example, a standard set has 5 rows of graduated blocks, each row containing 9 blocks giving total of 45 gauge blocks.



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ROW

GAUGE BLOCKS

GRADUATION

NUMBER

1

1.001 – 1.009

0.001

9

2

1.01 – 1.09

0.01

9

3

1.1 – 1.9

0.1

9

4

1.0 – 9.0

1.0

9

5

10.0 – 90.0

10.0

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Gauge blocks are made with 3 different grades of accuracy, depending on the purpose for which they are used:-

1. Accuracy degree 00 : for laboratories or master set, is accurate to 0.00005 mm 2. Accuracy degree 0 : for setting instruments with high precision, is accurate to

0.00015 mm 3. Accuracy degree 1 : for checking test gauges and setting length measurement instruments, provide as working set in workshop, is accurate to 0.00025 mm 2.4.1 Procedure

• Starts the combination with the last figure of the dimension required and eliminates the last place of decimals first.

• Continue to build up the dimension working from right hand side. • Gauge block combination should comprise as few gauge block as possible so that the

total error (size deviation) is kept to a minimum

Example: Required length = 50.255 mm Subtraction

1st gauge block = 1.005 49.250 2nd gauge block = 1.050 48.200 3rd gauge block = 1.200 47.000 4th gauge block = 7.000 40.000 5th gauge block = 40.000 00.000 50.255



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2.4.2 Handling and Maintenance

• clean the gauge blocks with kerosene or chamois before used • a combination of gauge blocks should not be wrong together for a long item ( than 6

hours ) otherwise the cold welding on the smooth measuring surfaces will be formed • after used, each gauge block should be greased with non-acidic paraffin jelly • must be protected from heat

3. EQUIPMENT / APPARATUS

3.1 Vernier Caliper 3.2 Micrometer 3.3 Steel ruler 3.4 Variety type of samples (blocks)

4. PROCEDURES

4.1 Perform a group of five students. 4.2 Each group will take 6 different sample of products with different shapes.

4.3 Draw the specimen and label the entire dimensions

4.4 By using the measuring equipments provided, measure all the dimensions of the

sample that is depth, outer diameter, inner diameter, length, and width.

4.5 Take minimum 3 readings of the measurement and insert the data in the table provided.

4.6 Calculate the average of the measuring readings.

4.7 Repeat the measurement for all the dimensions. After finish, change the sample

with the other group.

4.8 Repeat all the steps with the other 5 samples.

lab 1: metrologyportal.unimap.edu.my/portal/page/portal30/lecture...

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