Precision Measurement for Machinists
Course Outline

Lesson 1: Basic Print Reading [ Top ]

After completing this lesson the operator will be able to:

  1. Identify the following on a print:
    1. Multi-view print and explain its relationship to part features
    2. Workpiece features and their locations on a print
    3. A half section and full section view
    4. A detail view
    5. An auxiliary view
    6. A center line
    7. Both object lines and hidden lines
    8. An extension line
    9. A dimension line
    10. Leader line
    11. A cutting plane line and its reference notation
    12. A line
    13. A datum feature
    14. A coaxial and coplanar datum feature
    15. A datum target feature
  2. Explain the following abbreviations and symbols on a print:
    1. DIA, D, Ø
    2. R, RIA, RAD
    3. TIR, FIR, FIM
    4. TYP, 2X, 3X
    5. MAX
    6. MIN
    7. C, CFR, CHAM
    8. Surface Finish Symbol
    9. Counter Bore, Counter Sink, Depth Symbols
  3. The Title Block and Tolerances.
    1. Identify the Title Block
    2. Identify the Notes Area
    3. Explain Nominal Dimension
    4. Identify Basic Dimensions
    5. Identify Reference Dimensions
    6. Datum vs. Chain Dimensioning
    7. Find Missing Dimensions
  4. Explain the two common systems of measurement.
    1. Inch and Metric System principles
    2. Elements of the Inch System
    3. Elements of the Metric System
    4. Visualize dimensions and estimate sizes
    5. The factors used to convert inch and metric measurements

Lesson 2: Geometric Dimensioning and Tolerancing [ Top ]

After completing this lesson the operator will be able to:

  1. Describe practical benefits of GDT in manufacturing.
  2. Explain concepts and terms of basic geometry as used in manufacturing, including:
    1. Point
    2. Line
    3. Plane
    4. Two dimensional coordinate grid
    5. Three dimensional coordinate grid
    6. Origin of coordinate grid
    7. Positive and negative coordinates
    8. Circle, circumference, diameter and radius
    9. Cylinder
    10. Parallelism
    11. Perpendicularity
  3. Name and describe the five types of geometric tolerances.
    1. Form
    2. Orientation
    3. Location
    4. Runout
    5. Profile
  4. Name and describe the three types of Material Condition Modifiers.
    1. Maximum Material Condition (MMC)
    2. Least Material Condition (LMC)
    3. Regardless of Feature Size (RFS)
  5. Describe the benefits of true positioning location over "coordinate" location tolerancing.
    1. Explain True Position tolerancing
    2. Explain Coordinate location tolerancing
  6. Describe how GDT location tolerances also control the form of part features.
  7. Read and interpret a GDT Feature Control Frame.

Lesson 3: Datums and Bonus Tolerance [ Top ]

After completing this lesson the operator will be able to:

  1. Describe the major methods of measuring Geometric dimensions.
    1. Functional gages
    2. Open setup inspection
    3. Optical comparator
    4. Air gages
    5. Coordinate measuring machine (CMM)
  2. Describe why Datums are used for measuring Geometric dimensions
  3. Determine the correct order in which to establish Datums, given a Feature Control Frame callout
  4. Establish the correct number of points of contact when establishing Datums, based on the type of feature and the Datum order
  5. Establish Datums for measurement, including flat surfaces, linear elements along a cylindrical feature, rotational axes, slots or tabs.
  6. Describe how Bonus Tolerances are possible based on material condition modifiers
  7. Given a part print and workpiece, calculate a bonus tolerance
    1. Functional gages
    2. Open setup inspection
    3. Optical comparator
    4. Air gages
    5. Coordinate measuring machine (CMM)
  8. Calculate with Signed Numbers
    1. Explain the rules for adding signed numbers
    2. Explain the rules for subtracting signed numbers
    3. Calculate with signed numbers

NOTE: Geometric Dimensioning and Tolerancing Job Aids are provided with the training system. These Job Aids cover each GDT tolerance in detail, including suggested measuring equipment and techniques.

Lesson 4: Using the Inch and Metric Systems [ Top ]

After completing this lesson the operator will be able to:

  1. Explain the elements of Metric measuring system
    1. Identify the thousandths, hundredths, tenths and whole millimeter places in a dimensional value
    2. Relate the centimeter and millimeter to the inch
    3. Estimate Metric measurements based on relations to the inch
    4. Locate Centimeter divisions on a scale
    5. Locate Millimeter divisions
  2. Locate and identify the following features on an Inch dimension
    1. One inch, decimals, fractions
    2. When fractions and decimals are used
    3. Half, quarter, eighths, sixteenths, thirty seconds and sixty fourths
    4. Thousandths, hundredths, and tenths of an inch and how they relate
    5. How decimals and fractions differ and converting between them
    6. Converting between the inch and metric systems
    7. Rounding to the correct number of decimal places
    8. Calculate Tolerance limits
    9. Running Tolerance limits
    10. Perform shop math calculations: add, subtract, multiply, and divide
  3. Explain how to avoid Common errors in calculation
    1. Use mental estimation before calculation
    2. Avoid Transposition of numbers
    3. Avoid mistakes when entering values
    4. Communicate values correctly in inch and metric
  4. Factors which effect a measurement
    1. Cleanliness
    2. Temperature
    3. Gage accuracy
    4. Gauge setting
    5. Workpiece Deformation
    6. Gage deformation
    7. Proper measuring technique
  5. The Steel Rule
    1. Tolerances that allow the use of a Steel Rule
    2. Smallest measurement = to .010 or 1/64, or .5 mm
    3. Sizes of rules
    4. Dual dimensioned Steel Rules
    5. Three causes of errors: Worn edge, rule not parallel, parallax error
    6. Count whole units to feature end point
    7. Count remaining unit spaces to end point
    8. Total the measurement
    9. Write down the value correctly for the feature measured
    10. Care and handling of the steel rule

Lesson 5: Analog and Digital Micrometers [ Top ]

After completing this lesson the operator will be able to:

  1. Identify features of Metric and Inch micrometers
    1. Identify major parts of the micrometer
    2. Locate the baseline and zero point
    3. Locate 100 thousandths division lines
    4. Locate the 25, 50, 75 thousandths lines
    5. Locate the thimble and thousandths division lines
    6. Locate whole and half mm divisions on metric micrometer
    7. Locate thimble scale on metric Micrometer
    8. OD & ID
    9. Depth
    10. Thread
    11. Special mics
  2. Use and care of a conventional micrometer
    1. Clean Workpiece and Micrometer
    2. Rapidly open and close the micrometer
    3. Different ranges of micrometers
    4. Close with proper tension a micrometer using a friction thimble or ratchet stop
    5. Close with proper tension a micrometer which has a friction knob
    6. Check zeroing of micrometer
    7. Explain thimble rotation and resulting spindle travel
    8. Hold the micrometer properly
    9. Properly fit the micrometer to the workpiece to read the required dimension
    10. Changes in feel for round of cylindrical workpieces (reduce pressure to avoid compression of the piece)
  3. Read and total micrometer measurements
    1. Determine whole inch spaces
    2. Determine 100 thousandths spaces
    3. Determine 50 thousandths spaces
    4. Determine number of the 25 thousandths
    5. Write down values starting with micrometer size
    6. Align decimal points and total
    7. Identify the vernier scale and the tenth
    8. Read the vernier scale correctly
    9. Correctly total a measurement using a vernier instrument
    10. Ten-to-one rule
    11. Determine whole mm
    12. Determine half mm spaces
    13. Determine hundredths on sleeve
    14. Locate vernier scale on metric mic
  4. Identify and use Digital Mics
    1. Identify the types of digital micrometers
    2. Features of mechanical digital mics
    3. Measure with a mechanical digital mic
    4. Read the measurement
    5. Features of electronic digital mics
    6. Measure with an electronic digital mic
    7. Read the electronic measurement
    8. Store and maintaining the instrument

Lesson 6: Using Calipers and Go, No-Go Gages [ Top ]

After completing this lesson the operator will be able to:

  1. Identify caliper components and types of measurements
    1. Find lengths or outside diameters using the Outside Jaws
    2. Find inside diameters using the caliper blades
    3. Find recesses and depths using the depth rod
    4. Locate and explain the use of the Beam
    5. Locate and explain the use of the Outside and Inside Jaws
    6. Locate and explain use of the Depth Rod
    7. Locate and explain the use of the Slide
    8. Locate and explain the use of the Dial
    9. Locate and explain the use of the Vernier scale
    10. Explain the relationship between the divisions on the Beam and the Vernier scales
    11. Explain the "offset" jaw caliper and its two vernier scales
  2. Measure a workpiece feature using a Dial Caliper
    1. Check the calipers for proper adjustment and operation
    2. Clean the workpiece and calipers, and fit the calipers to the workpiece
    3. Apply the proper pressure during the measurement
    4. Use the Knife Edges properly for measuring grooves
    5. Rotate workpiece to find true diameter
    6. Read the number of whole inches on the Beam
    7. Read the number of hundreds of thousandths on the Beam
    8. Read the dial to determine the number of thousandths
    9. Total the measurement
    10. On a Metric Caliper, determine if centimeters or millimeters are used on the Beam
    11. Read the number of Beam units as millimeters
    12. Read the number of hundredths of a millimeter on the dial
    13. Add the readings to determine the measurement
    14. Clean and store the calipers when finished
  3. Measure a workpiece feature using a Vernier Caliper
    1. Explain the process of locating the matching lines on vernier scales
    2. Explain the beam and vernier divisions on a vernier caliper
    3. Locate the start point of the measurement
    4. Make an accurate measurement using an inch vernier caliper
    5. Locate the scales and divisions on an inch/metric caliper
    6. Using the metric scale, make an accurate measurement
    7. Describe how to determine the match line as it relates to the relative location to the tolerance allowed
  4. Understand digital calipers
    1. Locate and identify the features
    2. Explain the auto-shutoff feature
    3. Convert between metric and inch measurements
    4. Zero the digital caliper at any point
    5. Read measurements with signed numbers
  5. Using Go and No-Go gages
    1. Identify and explain the use of Go, No-Go gages
    2. Explain the components of, and properly use, snap gages
    3. Explain the use of Functional gages
    4. Explain and properly use Plug and Pin gages
    5. Explain and properly use Ring gages
    6. Explain what to do if a feature fails a Go, No-Go test

Lesson 7: Measuring Surface Finish [ Top ]

After completing this lesson the operator will be able to:

  1. Identify Characteristics of Surface Finish
    1. Roughness
    2. Waviness
    3. Lay
    4. Flaws
  2. Identify Units of measure for Surface Finish
    1. Explain Profile and Nominal Profile
    2. Identify and explain Microinches and Microns
    3. Identify peaks and valleys
    4. Identify and explain Ra and Aa
    5. Identify and explain the surface finish symbol and its components
  3. Comparison Gages
    1. Understanding Comparison Gages
    2. Range of Comparison Gages
    3. Use a Comparison Gages to Measure Surface Finish
  4. Analog and Digital Profilometers
    1. Components of analog profilometers
    2. Explain cutoff
    3. Range of analog profilometers
    4. Set up and measure with analog profilometers
    5. Set up and measure with digital profilometers
  5. Portable Surface Roughness Gage
    1. Uses for the Roughness Gage
    2. Identify components of the gage
    3. Calibrate the gage
    4. Measure Workpiece roughness

Lesson 8: Optical Comparators and Thread Measurement [ Top ]

After completing this lesson the operator will be able to explain:

  1. Identify the Elements of Threads and Thread Notation
  2. Locate and explain the elements of threads
    1. Thread Crest
    2. Thread Root
    3. Pitch versus Pitch Diameter
    4. Lead of a thread
    5. Major Diameter of OD and ID threads
    6. Pitch Diameter
    7. Minor Diameter of OD and ID threads
    8. How Geometric Tolerances apply
  3. Read and explain Print Notation of threads
    1. The Unified Inch Screw standard
    2. UNC, UNF, UNEF, UNJC, NPT and ACME designations
    3. Understanding Major Diameter notation and actual class size
    4. Locating the tolerances of Pitch Diameters on a chart
    5. Identifying the Threads Per Inch
    6. Calculate the Pitch from the TPI value
    7. Class of Fit and Hand designations
  4. Read and explain Metric Notation on a shop print
    1. Identify "M" (metric) symbol
    2. The nominal major diameter in millimeters
    3. The Pitch in a the metric thread notation
    4. Metric Coarse Threads: Look up and read the thread Pitch from a chart of metric thread standard dimensions
    5. Metric Fine Threads: Read the thread Pitch behind the "times sign"
    6. Describe the class of fit and g & h allowance notations
    7. State whether internal or external threads
    8. Read the Pitch Diameter if shown
  5. Explain the Methods of Measuring Threads
    1. Explain the steps involved in thread measurement
    2. Clean threaded features and measuring instruments
    3. Explain the features that a GO gage is checking on an OD thread
    4. Based on print specifications, select the measuring instrument
    5. Use a Go, No-Go Snap gage for Major Diameter and Pitch Diameter
    6. Detecting no-go conditions for inch and metric gages
    7. Use a go, no-go Plug gage for ID threads
    8. Correctly use Ring gages for OD threads
    9. Measure Pitch Diameter using a Pitch Micrometer
  6. Use a Tri-Roll gage to measure Pitch Diameter
    1. Identify the parts of a tri-roll gage
    2. The effect of multi-thread rolls
    3. Read the values on the face of the dial indicator
    4. Locate the tolerance limit dimensions in reference materials
    5. Identify the tolerance limit represented by a Master gage
    6. Place the master in the gage
    7. Set the tolerance limit on the dial face (zero the dial)
    8. Calculate and mark the other tolerance limit on the dial
    9. Note the full rotations when Mastering the gage
    10. Place a workpiece into the gage
    11. Complete a measurement at several locations
    12. Visually check thread quality and finish
    13. Check thread crests and identify faulty conditions
  7. Use an Optical Comparator
    1. Identify the components of an optical comparator with digital display
    2. Identify the axes of motion
    3. Identify the rotational axis of the table
    4. Explain the divisions on the screen grid
    5. Explain how the grid divisions change with changes in magnification
    6. Mount a threaded workpiece to the stage
    7. Set the angle of the table to the Helix Angle
    8. Focus the shadow
    9. Complete a root radius measurement
    10. Complete a feature length measurement
    11. Complete a angle measurement
    12. Measure a radius by matching to the grid arcs
    13. Identify Gage Charts and their magnification settings
    14. Read the limit lines scribed on a Gage Chart

Lesson 9: Open Setup Inspection [ Top ]

After completing this lesson the operator will be able to:

  1. Use an Indicator
    1. Identify components of dial and test indicators
    2. Interpret the reading on a dial face
    3. Explain the difference between balance dials and continuous dials
    4. Select the correct contact point for a dial indicator
    5. Set up an indicator properly for measurement
    6. Select the correct indicator (range, inch/metric)
    7. Explain typical applications of indicators in inspection
  2. Use Surface Plates and Holding Devices
    1. Describe surface plates and explain when they are used
    2. How to work with surface plates to avoid damaging them
    3. Fixture workpieces using the appropriate equipment
    4. Fixture workpieces by the proper feature for measurement
    5. Identify and use V-blocks
    6. Identify and use a Tri-Roll
    7. Explain Coaxial datum features
    8. Identify and use Parallel bars
    9. Identify and use Gage blocks for workpiece fixturing
  3. Use Gage Blocks
    1. Describe uses of gage blocks
    2. Identify a typical set of shop-grade gage blocks
    3. Explain how to select gage blocks for a given dimension
    4. Explain how to properly clean and wring gage blocks
  4. Use Mechanical Height Gages
    1. Identify the components of mechanical height gages
    2. Types of workpiece contact devices: test indicators, depth rod, scriber
    3. Rough and fine adjustment methods
    4. Vernier scales, dials, and digital readouts on height gages
    5. Using a Master height gage to create or measure a height setting
    6. How to use a Sweep height gage

Lesson 10: Coordinate Measuring Machines [ Top ]

After completing this lesson the operator will be able to:

  1. Identify and explain the purpose of CMMs and their components
    1. Identify the types of CMMs found in shops
    2. Explain the advantages of a CMM
    3. Identify the basic components of a CMM
    4. Identify the axes of motion
    5. Locate the Ways and their need for cleanliness
    6. Locate the Axis Control Switches and explain their operation
    7. Locate and explain the Manual Axis Controls
    8. Locate and explain the features of the Probe and Probe Tip
    9. Explain the use of an Indexable head
    10. Explain the purpose of the Computer
    11. Locate the Icons and their purpose
  2. Prepare for Measurement
    1. Explain when it is necessary to HOME the CMM
    2. Locate the Surface Plate and its mounting holes
    3. Locate and explain the purpose of the Qualification Sphere
    4. Clean the Surface Plate
    5. Prepare the workpiece for measurement
    6. Locate the piece and align a major axis to a CMM axis
    7. Clamp the piece correctly
    8. Locate and explain the coordinate display
    9. Locate the origin and datums of a feature
    10. Explain why the grid system is aligned to the origin of the features
    11. Explain when a probe tip must be changed
    12. Remove and replace a probe tip using the correct wrench
    13. Explain why the new tip must be qualified
    14. Start the Qualification process on the computer
    15. Explain when Multi-tip or Single Tip is to be used
    16. Move the probe in all three axes
    17. Properly touch-off the probe on the qualification sphere
    18. Explain the screen display and delete a hit
    19. Click DONE and explain the measured diameter value
    20. Locate and explain Standard Deviation values
    21. Locate and explain the Status Line values
  3. Align the CMM Coordinate System to a Feature's Datums
    1. Explain the auto-naming process of features and datums
    2. Clear any existing auto named features
    3. Identify stored measurement sequences from the file list
    4. Check the Status Line to confirm Alignment status
    5. Perform a CLEAR ALIGNMENT sequence.
    6. Locate the datums assigned to the features to be measured
    7. Use the PLANE function to locate a datum surface
    8. Auto-name the Plane and check standard deviation
    9. Explain what to do when Standard Deviation is incorrect
    10. Use the LINE function to locate a datum and auto-name it
    11. Use the CIRCLE function to locate a hole and auto-name it
    12. Complete an alignment process using the assigned datums
  4. Perform Common Measurement Procedures
    1. Explain and select a TRUE POSITION measurement sequence
    2. Touch-off a hole to find True Position
    3. Set the screen display to True Position MMC
    4. Locate and enter the Nominal print coordinates of X and Y
    5. Locate and enter the Nominal diameter value
    6. Locate and enter the Upper and Lower tolerance limits
    7. Locate and explain the True Position measured values
    8. Complete the sequence on other features making adjustments to the nominal values as required
    9. Explain and select an ANGLES measurement sequence
    10. Use a line-to-line sequence
    11. Touch-off the first line feature in the correct direction
    12. Touch-off the second line feature in the correct direction
    13. Complete the sequence and display the correct angle and deviation
    14. Explain and select a PERPENDICULARITY measurement sequence
    15. Use a Bore / Plane sequence
    16. Touch-off circles within the bore at two locations
    17. Recall the named Plane
    18. Complete the sequence and display the correct value and standard deviation