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Measuring tools Modern engines use thinner casting and require more precise measuring - PowerPoint PPT Presentation


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Measuring tools Modern engines use thinner casting and require more precise measuring. Selectively fit engines. All parts are measured and marked according to size Then selectively assembled for optimum clearance. Copyright 2003 Gary Lewis - Dave Capitolo. Tolerance limits

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Presentation Transcript
slide1

Measuring tools

    • Modern engines use thinner casting and require
    • more precise measuring

Selectively fit engines

  • All parts are measured and marked according to size
  • Then selectively assembled for optimum clearance

Copyright 2003 Gary Lewis - Dave Capitolo

slide2

Tolerance limits

  • The minimum and maximum allowable diameters
  • Specified clearance
  • Difference in diameters for
  • mating parts
  • Specified clearance of
  • replacement part should
  • be used
slide3

Example of tolerance limits for crankshaft and housing bore

    • Standard shaft size 1.9995/2.0005 in.
    • Housing bore diameter 2.1245/2.1250 in.
  • Clearances
    • Difference between shaft OD and bearing ID
    • Minimums and maximums
slide4

Maximum bearing inside diameter

    • Maximum housing bore +2.1250 in.
    • Bearing thickness -.0615 in.
    • Bearing thickness -.0615 in.
    • Max bearing inside diameter 2.0020 in.
  • Minimum bearing inside diameter
    • Minimum housing bore +2.1245 in.
    • Bearing thickness -.0615 in.
    • Bearing thickness -.0615 in.
    • Min bearing inside diameter 2.0015 in.
slide5

Minimum bearing clearance

    • Minimum bearing ID +2.0015 in.
    • Maximum crankshaft diameter - 2.0005 in.
    • Minimum bearing clearance .001 in.
  • Maximum bearing clearance
    • Maximum bearing ID +2.0020 in.
    • Minimum crankshaft diameter - 1.9995 in.
    • Maximum bearing clearance .0025 in.
slide6

Example of valve stem clearance

    • Valve stem diameter .3405 - .3415 in.
    • Stem-to-guide clearance .0015 - .0025 in.
  • To find valve guide diameter
    • Minimum clearance .0015 in.
    • Maximum stem diameter +.3415 in.
    • Valve guide diameter .3430 in.
  • Or…
    • Maximum clearance .0025 in.
    • Minimum stem diameter +.3405 in.
    • Valve guide diameter .3430 in.
slide7

Thermal expansion

    • Engines are assembled at room temperature
    • An error at room temperature may cause problems at
    • operating temperature
  • Coefficient of thermal expansion
    • Iron and steel .000006 in.

Aluminum .000012 in.

slide8

Example from book

    • Pin diameter .9000”
    • Pin bore diameter .9005”
    • Clearance at room temp .0005”
    • Pin diameter with 250° F change .9013”
    • Pin bore with 250° F change .9032
    • Clearance with 250° F change .0019”

Heat during machining

Rough and finish machining

Measuring tools at room temperature

slide9

Units of measure for linear measurement

  • 1 mm = .03937”
    • .1 mm = .003937”
    • .01 mm = .0003937”
    • .001 mm = .00003937”

To convert inches to millimeters

Inches times 25.4 or

Inches divided by .03937

  • To convert millimeters to inches
      • Millimeters divided by 25.4 or
      • Millimeters times .03937
slide10

Measuring tools

    • Outside micrometer
  • Inside micrometer
  • Depth micrometer
  • Telescoping gauge
  • Split ball gauge
  • Dial indicator
  • Dial bore gauge
  • Calipers
slide11

Outside micrometer

  • Screw pitch of 1/40” or .025” for inch micrometer
  • Screw pitch of .50 mm for metric micrometers
  • One inch of travel
  • Resolution limit of .0001” for inch micrometers
  • Resolution limit of up to .001 mm for metric
  • Calibrated with standards or gauge blocks
slide12

Depth micrometer

  • Used for measuring deck clearance, stepped flywheels
  • Screw pitches same as outside micrometer
  • One inch of travel
  • Resolution limit of .001” for inch micrometers
  • Scales are read in reverse order
  • Calibrated with gauge blocks and surface plate
slide13

Inside micrometer

  • Used for measuring cylinder bores, housing bores
  • Screw pitches same as outside micrometer
  • One inch of travel
  • Used more often with ‘transfer’ measurements
slide14

Transfer measurement

  • Adjust inside micrometer to size
  • Measure with an outside micrometer
  • Other tools include telescoping and split ball gauges
slide15

Dial indicators

  • Resolution limits printed on dial face
  • Used for checking straightness of cams and cranks
  • Read TIR (total indicator reading)
  • Check out-of-roundness first
slide16

Dial bore gauge

  • Used for cylinder bores and main bores
  • Uses ‘comparative’ measurement
  • Set up in a setting fixture or outside micrometer
  • Measure differences in the size that was set
slide17

Calipers

  • Dial and digital calipers
  • Lack of rigidity limits accuracy to .002”
  • Easy to read
slide18

Surface finish

  • Crank journals 10 AA micro inches
  • Head and block deck surfaces 20–60 AA micro inches
  • Cylinder bores 10-15 AA for moly rings
  • 25-30 AA for iron and chrome
slide19

Fastener terminology

Major diameter - Largest thread diameter

Minor diameter - Smallest thread diameter

Pitch - Distance between threads

Threads per inch - Number of thread in a linear inch

Grade - A system of grading fastener strength

slide20

Threaded fasteners

  • Bolts, machine screws, and capscrews stretch
  • when tightened
  • Fasteners have an elastic limit, then fracture occurs
  • Below elastic limit, fasteners can be tightened repeatedly
slide21

Necked down bolt

  • Example of a bolt that has been necked down. Tightening
  • past its elastic limit
slide22

Fastener strength

    • Cross section of threads
    • Minor diameter effects strength
    • As pitch increases on external threads, crossection
    • decreases
    • As pitch increases on internal threads, crossection
    • increases
slide23

Fastener strength

Heat treatment

  • Low strength fasteners are made of low carbon mild steel
  • High strength fasteners have added carbon for heat treating
  • SAE fasteners have marks for strength
  • Metric fasteners have numbers for strength
slide24

Thread identification

  • Outside diameter of the threads with a micrometer
  • Measure pitch with thread pitch gauge (threads per inch)
  • For the machine screw 10-32
  • Diameter: 10 x .013 + .060 = .190 in.
  • Pitch: 32 threads per inch = .031 in.