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MET 33800 Manufacturing Processes

Chapter 35

Measurement and Inspection

Unless otherwise indicated, illustrations in this presentation are taken from the 11th Edition of Degarmo’s Materials and Processes in Manufacturing textbook by J.T. Black and Ronald A. Kohser, ©2012, Wiley.

MET 33800 Manufacturing Processes

Chapter 35

Measurement and Inspection

Definitions

Measure To determine the dimension, quantity or capacity of something.

Measurement Act of measuring, fundamental activity of inspection.

Inspection Measuring conformance to design specifications (characteristics).

Chapter 35 ‐ 3

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Definitions (continued)

Attribute Measurement Uses gages that determine acceptance or rejection based on design specifications including visual and functional inspection.

Variable Measurement Uses calibrated instruments used to determine size.

Chapter 35 ‐ 4

Figure 35‐32 page 987


Definitions (continued)

Metrology The science of measurement.

Linear Metrology Measurement of linear dimensions (length, depth, diameter).

Chapter 35 ‐ 5

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Measurement Systems

U.S. Customary System English system

Conversion factors shown in table 35‐2 pg. 961.

International System of Units S.I. or metric system

Fundamental Units Based on physical phenomena (except mass). All other units derived from fundamental units.

Listed in table 35‐1 pg. 959.

Chapter 35 ‐ 6

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Chapter 35 ‐ 7

Measurement Systems (continued)

Chapter 35 ‐ 8

Primary Standard International standard.

Transfer Standard Traceable to primary standard. Lower accuracy than primary standard.

Traceability Links instrument and transfer standard to primary standard.

Measurement Systems (continued)

Chapter 35 ‐ 9

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Metrology Standard Responsibility:

National Institute of Standards and Technology (NIST)

International Bureau of Weights and Measures (Paris)

Measurement Systems

Chapter 35 ‐ 10

One thousands of an inch (0.001) is the basic unit of measuring in most manufacturing environments.

One thousands of an inch is typically referred to and “one” so when someone says plus or minus “five” they mean ±0.005 inch.

The next level of discrimination is referred to as a “tenth” so plus or minus “2 tenths” = ± 0.0002 in.

Finally when a machinist talks about “millionths” they are referring to 0.000 001 so ± 5 millionths is ± 0.000 005 and ±15 millionths is ±0.000 015. (0.000 001 = 1.0 in)

Shop Speak

Chapter 35 ‐ 11

Linear Standard Gage Blocks:

Standard of measurement in physical form.

Typically the ultimate standard of length in a manufacturing facility.

Used as a master gage comparison instruments.

Measurement Systems

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Figure 35‐2 Standard set of rectangular gage blocks.

Figure 35‐4 Wrung‐together gage blocks in special holder, used with a dial indicator to from an accurate comparator.

Measurement Systems

Chapter 35 ‐ 13

Linear Standard Gage Blocks

Developed by Carl Johansson (Sweden 1900).

Utilizes arithmetic progression to allow over 120,000 combinations with a discrimination of 0.0001 from a standard 81 piece set.

Accurate only at the Standard Temperature of Measurement, which is 68 F (20 C).

Measurement Systems

Chapter 35 ‐ 14

Available Gage Block Materials:

Tool Steel: 65 RHC, 6.4 in/in/F

Stainless Steel: 70 RHC, 5.5 in/in/F

Carbide: 70 RHC, 3.0 in/in/F

Chrome Carbide: 73 RHC, 4.7 in/in/F

Ceramic: 1400 HV, 6.4 in/in/F

Measurement Systems

Chapter 35 ‐ 15

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Accuracy Standards (table 35‐3 page 963):

Grade 0.5 ‐Metrology Laboratory Grade

Grade 1 ‐ Laboratory Grade

Grade 2 ‐ Precision Grade

Grade 3 ‐Working Grade

Measurement Systems

Chapter 35 ‐ 16

Chapter 35 ‐ 17

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Standard 81 piece Gage Block Set

Series 1: One Ten Thousandth Inch ‐ 9 blocks0.1001 ‐ 0.1009 in 0.0001 steps

Series 2: One‐Thousandth Inch ‐ 49 blocks0.101 – 0.149 in 0.001 steps

Series 3: Fifty‐Thousandths Inch ‐ 19 blocks0.050 – 0.950 in 0.050 steps

Series 4: Inch Series ‐ 4 blocks1.000 ‐ 4.000 in 1.000 steps

Measurement Systems

Chapter 35 ‐ 18

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Wringing (creating gage block stack‐ups):

Clean surfaces with conditioning stone and/or chamois.

Overlap surfaces slightly.

Slide and rotate with light finger pressure.

If blocks are in good condition they will wring (cohere) with a 1‐2 in gap.

Measurement Systems

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Accuracy and Precision Measuring systems are subject to variability from many sources including the measuring instrument, operator and environment.

We distinguish between accuracy and precision when considering variability.

Chapter 35 ‐ 20

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Accuracy and Precision Accuracy or Reliability is the difference between the observed average of the measurements and the true average. The true average represents the actual measurement determined by the most accurate method available. Accuracy is measured by central tendency.

Chapter 35 ‐ 21

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Precision or Repeatability is the variation in the measurements taken by one operator using the same instrument measuring the same characteristic on the same parts. Repeatability is measured by dispersion.

Reproducibility is the variation in the average of the measurements taken by different operators using the same instrument measuring the same characteristic on the same parts.

Accuracy and Precision

Chapter 35 ‐ 22

Chapter 35 ‐ 23

Accuracy and precision (if known) of a measurement should be included in report. At the minimum, the measuring instrument accuracy should be used.

Example:

length instrument accuracy ± 0.001 in

length reading 0.750 in

report measurement 0.750 ± 0.001 in


Chapter 35 ‐ 24

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Stability or Drift is the difference between the average of two sets of measurements taken with the same instrument, operator and parts but at different times.

Linearity is the difference in accuracy over the instrument's operating range. Linearity is typically measured as inches error/inch travel (in/in) or as a percentage of travel (%).


Chapter 35 ‐ 25

Discrimination is the finest division of the scale. The discrimination rule is to use an instrument with the desired discrimination

DO NOT estimate measurements on instruments with lower discrimination.

Discrimination is not equal to the instrument's accuracy.


Chapter 35 ‐ 26

Magnification or Amplification is the ratio of the readout scale graduation separation to the movement of the instrument's contact points.

Resolution or Sensitivity is the ability of an instrument to detect variations. A 0.001 sensitivity indicates than a variation of 0.001 or larger is necessary to cause a reaction by the instrument.


Chapter 35 ‐ 27

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Allowance and Tolerance Nominal (Basic) Dimension Ideal or theoretically

perfect dimension.

Tolerance Amount a characteristic can vary and still meets the design’s functional requirements. Methods of specifying tolerances:

Bilateral

Unilateral

Limit

±0.0051.000 +0.010- 01.000

1.010

1.000

Chapter 35 ‐ 28

Unilateral Basic dimension with either a positive or negative tolerance. Includes limit dimensions. Typically used for mating components in assemblies.

Bilateral Basic dimension with both a positive and negative tolerance. Tolerance may or may not be equally divided.

Allowance and Tolerance

Chapter 35 ‐ 29

Allowance Amount of clearance between mating components.

Positive allowance clearance for free fits.

Negative allowance interference for press fits.


Chapter 35 ‐ 30


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ANSI Allowance Standards (see Table 35‐4 pg. 968)

Class 1 Loose fit

Class 2 Free fit liberal allowance

Class 3 Medium fit sliding fits

Class 4 Snug fit zero allowance

Class 5 Wringing fit zero to negative allowance

Class 6 Tight fit slight negative allowance

Class 7 Medium force fit

Class 8 Heavy force or shrink fit permanent


Chapter 35 ‐ 31

ISO System of Limits and Fits: more complex than ANSI system.

Clearance fit positive allowance

Transition fit positive or negative allowance

Interference fit negative allowance


Chapter 35 ‐ 32

Geometric TolerancesGeometric Tolerances:

Based on perfect geometry (basic dimension).

Tolerance is allowable deviation of form or position –tolerance zone.

Incorporate modifiers to specify limit of linear dimensions.

Maximum Material Condition (MMC)

Least Material Condition (LMC)

Regardless of Feature Size (RFS)

Feature controls incorporate datum's or reference surfaces.

Chapter 35 ‐ 33

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Geometric Tolerance Symbols [Figure 35‐10 pg. 971]

Individual Features Form

Individual or Related Features Profile

Related Features Orientation, Location and Runout

Geometric Tolerances

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Chapter 35 ‐ 35

Basic Inspection Methods Pneumatic Air spindles and columns. Optical Light Energy

Toolmaker's microscopes. Optical comparators. Interferometers. Monochromatic lights and optical flats.

Optical Electron Energy Machine vision systems. Laser scanning. Laser interferometers.

Electronic LVDT’s. Mechanical Common instruments.

Chapter 35 ‐ 36

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Chapter 35 ‐ 37

Measuring InstrumentsInstrument types:

Direct Incorporates a line graduated scale. Can make measurement directly from instrument

Indirect No integral line graduated scale. Used to transfer measurement from part to direct measuring instrument.

Chapter 35 ‐ 38

Basic Rules of Measurement1. Measuring device should have an accuracy of at least

10 times better than the desired measurement accuracy (Rule of 10).

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2. Never estimate, read all line‐graduated scales to the nearest graduation using the discrimination of the measuring device. Reason ‐ linearity of the instrument

3. Avoid the use of excessive forces during measurement.

4. Avoid parallax error on all types of measuring devices.

Basic Rules of Measurement

Chapter 35 ‐ 40

5. Attachments can have the effect of decreasing the accuracy of the measurement.

6. Understand the hysteresis effect in the instrument and how it affects the measurement.

7. Reliable measurement possible only when the condition of the instrument is known.

8. Reliable measurement possible only when the instrument is in calibration.

Basic Rules of Measurement

Chapter 35 ‐ 41

Indirect Instrument Examples

Measuring Instruments

Chapter 35 ‐ 42

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Small HoleGage

Telescoping Gage

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STEEL RULE Common direct reading (line graduated) measuring instrument. Constructed with engraved graduations ('V' form) to an accuracy of 0.0003"/inch. Scale variations include fractional inch, decimal inch and metric.

Linear Measuring Instruments

Chapter 35 ‐ 43

STEEL RULE Procedure for use:

Align reference point on part with graduation, not end of rule.

Read to nearest graduation, do not estimate.

Avoid excessive force that might cause distortion or deflection of rule.

Avoid parallax errors by aligning eye perpendicular to graduations and both the reference point and measured point.


Chapter 35 ‐ 44


Steel Rule: Correct Usage Method

Chapter 35 ‐ 45

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Linear Measuring InstrumentsSteel Rule Variations Combination Square

Chapter 35 ‐ 46

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VERNIER INSTRUMENTS Vernier scale system developed by Pierre Vernier (1631). Vernier scale and slide caliper combined by Joseph Brown (1851).

Construction consists of a main frame that incorporates the fixed jaw and main scale; a moveable jaw, which incorporates the Vernier scale; and a clamping screw or integral spring used for error reduction.


Chapter 35 ‐ 47


Chapter 35 ‐ 48

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Vernier scale system reading technique:

1. Read main scale to 1‐inch discrimination using zero on Vernier scale.

2. Read main scale to 0.100‐inch discrimination using zero on Vernier scale.

3. Read main scale to 0.025 (three lines between 0.100 graduations) or 0.050 (one line between 0.100 graduations) discrimination using zero graduation on Vernier scale.

4. Read Vernier scale to 0.001‐inch discrimination using graduation that coincides with a graduation on the main scale.


Chapter 35 ‐ 49


Chapter 35 ‐ 50

Vernier Reading Examples


Chapter 35 ‐ 51

3.075+0.0163.091

1.375+0.0131.388

Fig 6‐8, page 65, Basic Shop Measurement, National Machine Tool Builders’ Association, ©1983, John Wiley & Sons.

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Vernier Caliper procedure for use:

1. Align fixed jaw with reference point on part.

2. Position moveable jaw with measured point on part. Use a centralizing or rocking motion to insure accurate alignment.

3. Use fine adjustment screw if available using care not to distort the instrument frame.

4. Use clamping screw to reduce error if available.


Chapter 35 ‐ 52

Vernier Instrument Types Height, Depth Inside/outside/depth combination and protractors (angle measurement).

Dial Caliper Mechanical adaptation of dial indicator to slide caliper.

Digital Caliper Adaptation of electronic scale to slide caliper.


Chapter 35 ‐ 53


Chapter 35 ‐ 54

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Chapter 35 ‐ 55

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MICROMETER Micrometers are the most common of the direct reading instruments. Micrometers are designated by their largest opening. Major components include an anvil (0.250 diameter standard), which is used for the reference point; a spindle (0.250 dia standard), which is used for measured point; main scale engraved into barrel (0.025 discrimination); micrometer scale engraved into thimble (0.001 discrimination); and Vernier scale engraved into barrel (0.0001 discrimination).


Chapter 35 ‐ 56


Chapter 35 ‐ 57

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Micrometer procedure for use:

1. Place and hold anvil on part's reference point.

2. Bring spindle in contact with measured point.

3. Approach spindle contact slowly to avoid defeating the ratchet.

4. Use a centralizing or rocking motion to insure proper alignment.

5. Avoid excessive force that cause distortion or deflection.


Chapter 35 ‐ 58

Micrometer Reading Examples


Chapter 35 ‐ 59


Metric and English Micrometer Reading Examples


Chapter 35 ‐ 60

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Chapter 35 ‐ 61


Micrometer Reading Examples

Outside Micrometer Instrument Types:

Thread ‐ indicates pitch diameter.

Spline ‐ .118 diameter anvil and spindle

Ball ‐ incorporates spherical anvil

Tube ‐ incorporates cylindrical anvil

Point ‐ point contact on reference and measured surfaces


Chapter 35 ‐ 62

Outside Micrometer Instrument Types:

Disc ‐ sheet or plate applications

Hub ‐ small frame for through bore hub measurement

Blade ‐ reduced thickness anvil and spindle for grooves

Deep Throat ‐ sheet or plate applications

V‐Anvil ‐ three lobed part measurement


Chapter 35 ‐ 63

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Chapter 35 ‐ 64



Chapter 35 ‐ 65


Other Micrometer Instrument Types:

Depth: Interchangeable rods for increased range

Digital/Mechanical

Digital/Electronic

Inside caliper

Inside micrometer


Chapter 35 ‐ 66

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Chapter 35 ‐ 67

Page 53‐54, Basic Shop Measurement, National Machine Tool Builders’ Association, ©1983, John Wiley & Sons.

DIAL INDICATORS Dial Indicators are deviation or comparison type instruments. Deviation instruments are measuring devices that incorporate a line‐graduated scale (direct reading) but do not incorporate an integral standard. Comparison instruments require the use of an external standard or master for deviation type measurement. Dial indicators can be used for highly accurate and repeatable measurements.


Chapter 35 ‐ 68


Chapter 35 ‐ 69

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Chapter 35 ‐ 70Page 77, Handbook of Dimensional Metrology, Francis T. Farago

and Mark A. Curtis, ©1994, Industrial Press Inc.


Chapter 35 ‐ 71

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Other Dial Indicator Devices:

Test Indicators

Dial Snap Gages

Dial Bore Gages

Depth Gages

Indicating Micrometers


Chapter 35 ‐ 72

Page 110, Handbook of Dimensional Metrology, Francis T. Farago and Mark A. Curtis, ©1994, Industrial Press Inc.

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Test Indicators


Chapter 35 ‐ 73


Gages for Attribute Inspection:

FIXED‐TYPE GAGES Designed to gage only one dimension and indicate whether it is larger or smaller than the standard. Includes: Plug Gage, Ring Gages, Snap Gages, Flush Pin Gages, and Profile Gages.

DEVIATION‐TYPE GAGES Determines amount measurement deviates from a standard. Includes: Dial Indicators, Air Gages and LVDT’s.

Attribute Measurement

Chapter 35 ‐ 74


Chapter 35 ‐ 75Source Unknown

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Chapter 35 ‐ 76

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Source Unknown

Snap Gages


Chapter 35 ‐ 77

Plug and ring gages for various geometries.

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Chapter 35 ‐ 78


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Thread Form/Pitch Gages

Radius Gages

Chapter 35 ‐ 79



Testing

Chapter 35 ‐ 80

Reference: Page 233 Materials and Processes in Manufacturing, 9th

Edition, Degarmo, Black and Kohser, Wiley

Testing – Penetrant

Chapter 35 ‐ 81

Reference: Page 234Materials and Processes in Manufacturing, 9th

Edition, Degarmo, Black and Kohser, Wiley

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Testing – Penetrant

Chapter 35 ‐ 82

Fluorescent liquid penetrant inspection.

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Testing – Magnetic Particle

Chapter 35 ‐ 83

Reference: Page 235‐6 Materials and Processes in Manufacturing, 9th Edition, Degarmo, Black and Kohser, Wiley

Testing – Magnetic Particle

Chapter 35 ‐ 84

Fluorescent magnetic particle inspection.

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Testing – Ultrasonic

Chapter 35 ‐ 85


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Testing ‐ Radiography

Chapter 35 ‐ 86

Reference: Page 239 Materials and Processes in Manufacturing, 9th Edition, Degarmo, Black and Kohser, Wiley

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Weld Porosity

Testing – Eddy Current

Chapter 35 ‐ 87


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The End – See Oncourse for Videos

Chapter 35 ‐ 88

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