Russ Schultz and Larry Smith

Blueprint Reading for the Machine Trades, Sixth Edition Unit 2: Dimensioning Systems
Russ Schultz and Larry Smith PowerPoint presentation created by LaVonne Vichlach

Dimensioning Systems Four different systems of dimensioning used in U.S. and Canada Fractional inch Decimal inch Dual dimensioning SI Metric

Dimensioning Systems

Fractional type steel rules divided into units of:
1/16 1/32 1/64 Major graduation accentuated by longer lines Some have small numbers printed adjacent to lines

Fractional Dimensioning
Always reduce a fraction to its lowest terms If numerator is even number-it can be reduced Begin your count from a major graduation close to the reading

Fractional Dimensioning

Scale Reading Quiz 1 Record the scale length identified by 1 3/4

Scale Reading Quiz 1 Record the scale length identified by 2 1 5/8

Scale Reading Quiz 1 Record the scale length identified by 6 13/16

Scale Reading Quiz 1 Record the scale length identified by 7 1 ¾

Decimal Scales Subdivided into units of 1/10, 1/20, 1/50, or 1/100 in.
1/50 is sufficient for most applications With 50 increments to an inch each increment =.02 in. Reading between increments-capable of determining closest .01 inch measurement

Decimal Scales Closer measurements require using micrometer, vernier or dial calipers Major graduations are accented by longer lines-usually every 1/10 in. Popular scales graduation style has .04 and .06 increments slightly longer than .02 and .08 Reads faster, more recognizable

Decimal Scales

Scale Reading Quiz 2 Record the scale length identified by... 1 .80

Scale Reading Quiz 2 Record the scale length identified by… 2 1.60

Decimal Dimensioning Drawing may be dimensioned using two- or three-place decimals Amount of tolerance is determined by number of decimal places

Decimal Dimensioning .50 may have tolerance of ± .01

Decimal Dimensioning Converting fractions to decimals-results in too many decimal places Need to round off those numbers to desired places

Decimal Dimensioning Rule #1-When the figure following the last digit to be retained is greater than 5---increase the last number by one .016 becomes .02 .047 becomes .05 .078 becomes .08

Decimal Dimensioning Rule #2-When the figure following the last digit to be retained is less than 5---retain the last number .031 becomes .03 .062 becomes .06 .093 becomes .09

Decimal Dimensioning Rule #3-When the figure following the last digit to be retained is exactly 5 and the figure to be retained is odd---increase the last number by one .375 becomes .38 .875 becomes .88

Decimal Dimensioning Rule #4-When the figure following the last digit to be retained is exactly 5 and the figure to be retained is even---retain the last number .125 becomes .12 .625 becomes .62

Decimal Dimensioning Rule #3 and #4 are different
Established to even numbers as often as possible Even numbers are preferred Decimal numbers divided by two-e.g.-diameter/2 = radius-----results will contain same number of decimal places

Decimal Dimensioning

Decimal Rounding Quiz .11 .12 .16 .23 .44 .55 .56 .109 = .125 = .156 =
.234 = .438 = .547 = .562 = .12 .16 .23 .44 .55 .56

Decimal Rounding Quiz .64 .641 = .797 = .875 = 1.056 = 1.672 = 2.205 =
2.454 = .80 .88 1.06 1.67 2.20 2.45

Decimal Rounding Quiz 3.335 = 3.34 3.767 = 5.555 = 3.77 6.665 =
7.045 = 8.885 = 3.34 3.77 5.56 6.66 7.04 8.88

Metric Dimensioning Metric increment of measure is millimeter
Will be noted if different Dual dimensioning system-SI Metric-used in U.S. and Canada Convert a metric dimension to inches by multiplying it by

Metric Dimensioning Conversion charts are available to provide converted dimensions Metric scales are available and can be used-eliminating need for conversion

Metric Dimensioning Metric scales
Have graduations every millimeter of half-millimeter Designated “mm” or “1/2 mm” Every fifth millimeter is accentuated by a longer line Every tenth millimeter is identified by a number

Metric Dimensioning

Scale Reading Quiz 3 Record the scale length identified by 1 20 mm

Scale Reading Quiz 3 77.5 mm Record the scale length identified by 4

Scale Reading Quiz 3 93.5 mm Record the scale length identified by 5

Blueprints Blueprinting-Term can be interpreted as
Drawing Picture Contains information Required sizes Tolerances Essential requirements Notes and instructions

From the information on this drawing, could you make this part?

Could you make this one?

Engineering Drawings Original drawing made by drafter or engineer
Prints are referred to as engineering drawings Also referred to as blueprints (more common term)

Engineering Drawings Standardized drawings “A” size is 8 ½ x 11 inches
“B” size is 11 x 17 inches “C” size is 17 x 22 inches “D” size is 22 x 34 inches “E” size is 34 x 44 inches

Engineering Drawings

Engineering Drawings What are the basic dimensions of the A-size drawing? 8 ½ X 11 2. If C-size is twice as large as B-size, how much larger is it than A-size? 4X

Engineering Drawings Will an E-size print fold to fit in the same envelope with an A-size print? YES 4. What metric size is twice as large as the A3 size? A2

Engineering Drawings Are the A4 metric size and the A inch size exactly the same? (Use 1in = 25.4 mm or 1mm = in. to compare) NO

Title Blocks Each drawing contains a Title Block
Drawing number is most prominent lettering in title block Lettered larger to stand out Scale determines the size of the object drafted

Title Blocks Mechanical drawings may be reduced to Half size
Quarter size One eighth size

Title Blocks Mechanical drawings may be enlarged Double Four times
Ten times

Title Blocks Half scale---1/2, 1:2, or ½”=1”
Twice scale-2/1, 2:1, 2-1, 2”=1” or 2X Arrangement of numerals indicates relationship

Title Blocks Refer to scale as the “Do Scale”
“D” stands for the drawing “O” stands for the object Sale of 1:2 means The drawing is 1 inch Object is 2 inches A “Do Scale” of 2:1 means The drawing is 2 inches The object is one inch or one half the drawing size

Title Blocks

Drawing Notes Local notes-apply to specific item or area
Use leaders Direct notes to point of application General notes apply to whole drawing or product Machining Heat treat Material Tolerances

Drawing Notes Abbreviations are used in notes Keep them brief

Drawing Notes-General
UNLESS OTHERWISE SPECIFIED METRIC UNITS ARE MILLIMETERS FILS & RNDS ARE .12R PART SYM ABOUT CL

Drawing Notes-Local 5 HOLES EQL SP ON 6.000BC
.344 DR, .500 CBORE, .30 DP .281 DR, 82° CSK, .53 DIA

Drawing Notes Quiz What type of note applies to an entire drawing?
General

Drawing Notes Quiz What type of line is used with local notes? Leader

Drawing Notes Quiz Where do general notes appear on a drawing?
Above the title block

Drawing Notes Quiz Symmetrical and centerline
Interpret the abbreviations SYM and CL used in the third general note. Symmetrical and centerline

Drawing Notes Quiz Drill and countersink
Interpret the abbreviations DR and CSK used in the third local note. Drill and countersink

Single-View Drawings Sometimes adequate to describe object
Material thickness is listed

Detail Drawings “Production drawings” and “working drawings” are general terms Includes all types of engineering drawings

Detail Drawings Detail drawings include Sufficient number of views
Dimensions Notes Other pertinent information

Centerlines

Centerlines Intersecting centerlines drawn through each hole
Used for location-centerlines are extended outside view and dimensions are added Radii are the same-often share a common axis-common design practice

Diameters and Radii

Diameters and Radii Internationally recognized symbol for diameter 
Use in place of the abbreviation DIA Number of holes indicated

Diameters and Radii Overall dimensions can be calculated
Remaining material around hole can be calculated

Diameters and Radii Remaining material around hole can be calculated

Answer the questions

Thermostat Gasket 1. What is the part number? 11A001

Thermostat Gasket 2. What is the name of the part? Thermostat gasket

Thermostat Gasket 3. What is the drawing size? (A, B, or C) A

Thermostat Gasket 4. What scale is the drawing? 1:1

Thermostat Gasket 5. Use words to explain the answer to question 4.
Actual size

Thermostat Gasket 6. How thick is the part? .06

Thermostat Gasket 7. Is the part symmetrical? Yes

Thermostat Gasket 8. Which system of dimensioning was used? (Refer to page 21.) Decimal

Thermostat Gasket 9. What is the fractional equivalent of the center hole size? (Refer to the equivalency chart, page 25.) 2 3/16

Thermostat Gasket What is the fractional equivalent of the mounting hole spacing? (Refer to the equivalency chart, page 25.) 3 5/8

Thermostat Gasket 11. Calculate the longest overall dimension of the part. 4.24

Thermostat Gasket 12. Calculate the overall dimension of the part (height.) 2.88

Thermostat Gasket 13. Calculate the material remaining between the large hole and the nearest outside edge. .345

Thermostat Gasket 14. Calculate the material remaining between the small hole and the nearest outside edge. .155

Thermostat Gasket 15. Calculate the material remaining between the large hole and the nearest small hole. .56

Break Lines Permits removal of a portion of view Paper size is smaller
Drawing scale can get smaller Portion removed must be uniform in shape

Break Lines Drawing is full size and does not require a “B” size drawing

Break Lines

Typical Dimensions Entered after a dimension
Means all other similar dimensions are same as one marked “TYP” Eliminates repetition of dimensions Saves on drawing space

Symmetry Indicated by note
Indicated by view’s centerline carrying abbreviation

Exercise Enter dimensions for the letters provided.

Bottom Plate A 1.50

Bottom Plate B 3.60

Bottom Plate C .30

Bottom Plate D 1.47

Bottom Plate E 6.10

Bottom Plate F 2.00

Bottom Plate G .19

Bottom Plate H .57

Bottom Plate I .86

Bottom Plate J .68

Bottom Plate K .10

Bottom Plate L .46

Bottom Plate 1. What type of line was drawn to indicate symmetry?
Centerline

Bottom Plate 2. What word is abbreviated TYP? Typical

Bottom Plate 3. What is the thickness of the plate? .25

Bottom Plate 4. How many round holes does the plate contain? 10

Bottom Plate 5. What is the fractional equivalent of the small hole diameter? 9/32

Bottom Plate 6. How much material remains between a .62 Dia. hole and the nearest outside edge? .25

Bottom Plate 7. How much material remains between a .28 Dia. hole and the nearest outside edge? .16

Bottom Plate 8. Calculate the longest overall dimension of the plate.
6.76

Tolerances Tolerances are assigned to every dimension
Assign maximum acceptable deviation-tolerance Shown with dimension Shown in the title block as a general tolerance

Tolerances General tolerances commonly assigned using decimals
Decimal dimension and tolerance have same number of places Most commonly expressed bilaterally-not always equal in both directions

Tolerances

Tolerance Quiz 1. What is the two place decimal tolerance in Example A?  .03

Tolerance Quiz 2. What is the tolerance for drilled holes in Example A? + .010 -.002

Tolerance Quiz 3. What is the three-place decimal tolerance in Example B?  .004

Tolerance Quiz 4. What is the fractional tolerance in Example C?
 1/64

Tolerance Quiz 5. What is the total tolerance for the two-place decimal inch in Example A?  .03

Tolerance Quiz What is the angular tolerance in Example C?  030’

Tolerance Quiz What is the total tolerance for the three-place decimal inch in Example B?  .004

Tolerance Quiz What is the total tolerance for drilled holes in Example A? + .010 -.002

Bolt Circles Three or more holes are positioned around a common center
Located angularly on a circular centerline

Bolt Circles Dimension of bolt circle appears
Inside of diagonal dimension line With abbreviation BC after hole data Holes may be equally spaced Abbreviation EQL SP follows quantity in local note Divide 360 by number of holes One of the holes is on vertical or horizontal centerline

Bolt Circles Inside of diagonal dimension line

Bolt Circles With abbreviation BC after hole data-Holes may be equally spaced Abbreviation EQL SP follows quantity in local note

Bolt Circles Holes may be located coordinately
Use only vertical or horizontal dimensions

Shim How thick is the shim? .020

Shim Is the shim symmetrical? No

Shim Are the bolt circles concentric? Yes

Shim How many holes are in the shim? 8

Shim What is the tolerance on the .250 Dia. holes? .005

Shim What is the tolerance on the .500 Dia. holes? .008

Shim What is the tolerance on the Dia. hole? .010

Shim What is the tolerance on the bolt circles? .010

Shim What is the tolerance on the radii? .02

Shim How much material is between the 5/8” hole and the nearest outside edge? .1875

Shim How far apart angularly are the three .500 Dia. holes? 120°

Shim How far apart angularly are a .250 Dia. hole and the nearest .500 Dia. hole? 60°

Shim How far apart angularly are a .250 Dia. hole and the farthest .500 Dia. hole? 180°

Shim How far apart angularly is the 5/8” hole from the nearest ½” hole? 30°

Shim What is the angular tolerance for the hole locations? ±0°30’

Shim What is the dimension for A? 1.15

Shim What is the dimension for B? 1.125

Shim What is the dimension for C? .625

Shim What is the dimension for D? .525

Shim What is the dimension for E? .275

Maximum & Least Material Condition
MMC Feature of size contains the maximum material within assigned tolerances

For a shaft At MMC when tolerance is added to its size dimension (.760) At LMC when tolerance is subtracted from it size dimension (.740)

Internal feature-hole-is at MMC when it is at its smallest size Sizes are exaggerated. NTS-Not To Scale

Internal feature-hole-is at LMC when it is at its largest size Sizes are exaggerated. NTS-Not To Scale

On any part All surfaces are features (they are not measurable-size) For LMC and MMC, the feature must have a size dimension Must be associated with tow opposing elements or two opposed parallel surfaces Must be measurable

A MMC LMC DOES NOT APPLY X

B MMC LMC DOES NOT APPLY 1.005 .995

C MMC LMC DOES NOT APPLY 3.005 2.995

D MMC LMC DOES NOT APPLY 1.30 1.32

E MMC LMC DOES NOT APPLY .349 .339

F MMC LMC DOES NOT APPLY .30 .32

G MMC LMC DOES NOT APPLY .66 .64

H MMC LMC DOES NOT APPLY X

I MMC LMC DOES NOT APPLY X

J MMC LMC DOES NOT APPLY .905 .895

K MMC LMC DOES NOT APPLY 1.91 1.89

L MMC LMC DOES NOT APPLY X

M MMC LMC DOES NOT APPLY .258 .248

N MMC LMC DOES NOT APPLY .370 .380

Allowance Minimum clearance between mating parts
Maximum interference between mating parts Calculate by subtracting MMC of shaft from MMC of hole

Allowance When shaft’s MMC is smaller than hole’s MMC-positive allowance-clearance When shaft’s MMC is larger than hole’s MMC-negative allowance-interference

Allowance Positive or negative-allowance is always the tightest possible fit between mating parts

Allowance Use the formula for calculating allowance:
MMC Hole - MMC Shaft = Allowance

Allowance MMC Hole =.999 -MMC Shaft A =.998 Allowance =.001 (positive)

Allowance MMC Hole =.999 -MMC Shaft B =1.004
Allowance =-.005 (negative)

MMC/Allowance Quiz What is the MMC of hole “D?” .748

MMC/Allowance Quiz What is the MMC of Shaft “C?” .745

MMC/Allowance Quiz What is the allowance between “C” and “D?’ .003

MMC/Allowance Quiz Is the allowance positive or negative? Positive

MMC/Allowance Quiz Is it a clearance or interference fit? Clearance

MMC/Allowance Quiz What is the MMC of hole “F?” .743

MMC/Allowance Quiz What is the MMC of shaft “E?” .747

MMC/Allowance Quiz What is the allowance between “E” and “F?” -.004

MMC/Allowance Quiz Is the allowance positive or negative? Negative

MMC/Allowance Quiz Is it a clearance or interference fit? Interference

MMC/Allowance Quiz What is the LMC of hole “D?” .752

MMC/Allowance Quiz What is the LMC of Shaft “C?” .735

MMC/Allowance Quiz What is the allowance between “C” and “D?’ .017

MMC/Allowance Quiz What is the LMC of hole “F?” .745

MMC/Allowance Quiz What is the LMC of shaft “E?” .743

MMC/Allowance Quiz What is the allowance between “E” and “F?” .002

Arcs And Circles When an arc is less than a complete circle-dimension it by radius May have a definite center-e.g R & 4.50R in Dwg. 11A004 May float-run tangent with other arcs or lines-e.g. .75R same print

Arcs And Circles Radial dimension not used for circles or diameters
Radial dimension doubles permit greater variation

Arcs And Circles E.g DIA with .01 yields dimension between .99 and 1.01 DIA .50R with .01 would permit diametric dimensions between .98 and 1.02 DIA

Arcs And Circles

Arcs And Circles Is the print drawn to (a) half-size or (b) twice-size? (a) half-size

Arcs And Circles What is the thickness of the spacer? .500

Arcs And Circles Interpret the abbreviation CRS used in the title block? Cold-Rolled Steel

Arcs And Circles How many holes does the spacer contain? 10

Arcs And Circles Is the spacer symmetrical about the vertical and horizontal centerline? Vertical

Arcs And Circles What is the angular dimension between each small hole? 60

Arcs And Circles What is the angular dimension between each large hole? 120

Arcs And Circles What tolerance is assigned to the angular spacing of the drilled holes?  030’

Arcs And Circles What is the tolerance on the bolt circles?  .01

Arcs And Circles What is the tolerance on the center hole diameter?
 .005

Arcs And Circles What is the MMC of the center hole? 4.995

Arcs And Circles What is the tolerance on the drilled holes? +.010
-.002

Arcs And Circles What is the MMC of the .688 holes? .686

Arcs And Circles What is the overall dimension along the horizontal CL? 9.00

Arcs And Circles What is the overall dimension along the vertical CL?
10.50

Arcs And Circles Enter the dimension for the letter “A.” .50

Arcs And Circles Enter the dimension for the letter “B.” .531

Arcs And Circles Enter the dimension for the letter “C.” 1.00

Arcs And Circles Enter the dimension for the letter “D.” .656

Arcs And Circles Enter the dimension for the letter “E.” .687

Arcs And Circles Enter the dimension for the letter “A.” .81

Arcs And Circles Enter the dimension for the letter “B.” 2.32

Arcs And Circles Enter the dimension for the letter “C.” .15

Arcs And Circles Enter the dimension for the letter “D.” 3.28

Arcs And Circles Enter the dimension for the letter “E.” 7.26

Arcs And Circles Enter the dimension for the letter “F.” 1.72

Arcs And Circles Enter the dimension for the letter “G.” 1.58

Arcs And Circles Enter the dimension for the letter “H.” .42

Arcs And Circles Enter the dimension for the letter “I.” 30°

Arcs And Circles Enter the dimension for the letter “J.” 3.98

Arcs And Circles Enter the dimension for the letter “K.” .01

Arcs And Circles Enter the dimension for the letter “L.” .20

Arcs And Circles Enter the dimension for the letter “M.” .19

Arcs And Circles Enter the dimension for the letter “N.” .12

Arcs And Circles Enter the dimension for the letter “0.” .30

Arcs And Circles How much material remains between a .250 hole and the outside edge? .225

Arcs And Circles How much material remains between a .220 hole and the outside edge? .19

Arcs And Circles Are the .200 holes located in the exact center between ID and OD? (Calculate this.) No

Arcs And Circles What is the MMC of the center hole? 2.555

Arcs And Circles What is the MMC of the .250 holes? .248

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