Blueprint reading for the machine trades sixth edition unit 2 dimensioning systems
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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

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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


Dimensioning Systems


Dimensioning Systems


Dimensioning Systems


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

  • 3/4

1


Scale Reading Quiz 1

Record the scale length identified by

  • 1 5/8

2


Scale Reading Quiz 1

Record the scale length identified by

  • 2 7/16

3


Scale Reading Quiz 1

  • 3 3/16

Record the scale length identified by

4


Scale Reading Quiz 1

  • 3 15/16

Record the scale length identified by

5


Scale Reading Quiz 1

  • 13/16

Record the scale length identified by

6


Scale Reading Quiz 1

  • 1 ¾

Record the scale length identified by

7


Scale Reading Quiz 1

  • 2 11/16

Record the scale length identified by

8


Scale Reading Quiz 1

  • 3 17/32

Record the scale length identified by

9


Scale Reading Quiz 1

  • 3 31/32

Record the scale length identified by

10


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


Decimal Scales


Decimal Scales


Decimal Scales


Scale Reading Quiz 2

  • .80

Record the scale length identifiedby...

1


Scale Reading Quiz 2

  • 1.60

Record the scale length identified by…

2


Scale Reading Quiz 2

  • 2.50

Record the scale length identified by…

3


Scale Reading Quiz 2

  • 3.32

Record the scale length identified by…

4


Scale Reading Quiz 2

  • 3.86

Record the scale length identified by…

5


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

  • .500 may have tolerance of ± .001

  • .5000 may have tolerance of ±.0001


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

  • .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

3.34

  • 3.335 =

  • 3.767 =

  • 5.555 =

  • 6.665 =

  • 7.045 =

  • 8.885 =

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 .03937


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

  • 20 mm

1


Scale Reading Quiz 3

Record the scale length identified by

2

  • 35 mm


Scale Reading Quiz 3

Record the scale length identified by

3

  • 51 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


What are the basic dimensions of the A-size drawing?

Engineering Drawings

8 ½ X 11

2. If C-size is twice as large as B-size, how much larger is it than A-size?

4X


Will an E-size print fold to fit in the same envelope with an A-size print?

A2

Engineering Drawings

YES

4. What metric size is twice as large as the A3 size?


Are the A4 metric size and the A inch size exactly the same? (Use 1in = 25.4 mm or 1mm = .03937 in. to compare)

NO

Engineering Drawings


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


Title Blocks


Title Blocks


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


UNLESS OTHERWISE SPECIFIED

METRIC UNITS ARE MILLIMETERS

FILS & RNDS ARE .12R

PART SYM ABOUT CL

Drawing Notes-General


5 HOLES EQL SP ON 6.000BC

.344 DR, .500 CBORE, .30 DP

.281 DR, 82° CSK, .53 DIA

Drawing Notes-Local


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

  • Interpret the abbreviations SYM and CL used in the third general note.

Symmetrical and centerline


Drawing Notes Quiz

  • 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


Break Lines


Break Lines


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

  • 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 1.000 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


Maximum & Least Material Condition

  • 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)


Maximum & Least Material Condition

  • Internal feature-hole-is at MMC when it is at its smallest size

Sizes are exaggerated. NTS-Not To Scale


Maximum & Least Material Condition

  • Internal feature-hole-is at LMC when it is at its largest size

Sizes are exaggerated. NTS-Not To Scale


Maximum & Least Material Condition

  • 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


X


1.005

.995


3.005

2.995


1.30

1.32


.349

.339


.30

.32


.66

.64


X


X


.905

.895


1.91

1.89


X


.258

.248


.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)


What is the MMC of hole “D?”

MMC/Allowance Quiz

.748


What is the MMC of Shaft “C?”

MMC/Allowance Quiz

.745


What is the allowance between “C” and “D?’

MMC/Allowance Quiz

.003


Is the allowance positive or negative?

MMC/Allowance Quiz

Positive


Is it a clearance or interference fit?

MMC/Allowance Quiz

Clearance


What is the MMC of hole “F?”

MMC/Allowance Quiz

.743


What is the MMC of shaft “E?”

MMC/Allowance Quiz

.747


What is the allowance between “E” and “F?”

MMC/Allowance Quiz

-.004


Is the allowance positive or negative?

MMC/Allowance Quiz

Negative


Is it a clearance or interference fit?

MMC/Allowance Quiz

Interference


What is the LMC of hole “D?”

MMC/Allowance Quiz

.752


What is the LMC of Shaft “C?”

MMC/Allowance Quiz

.735


What is the allowance between “C” and “D?’

MMC/Allowance Quiz

.017


Is the allowance positive or negative?

MMC/Allowance Quiz

Positive


Is it a clearance or interference fit?

MMC/Allowance Quiz

Clearance


What is the LMC of hole “F?”

MMC/Allowance Quiz

.745


What is the LMC of shaft “E?”

MMC/Allowance Quiz

.743


What is the allowance between “E” and “F?”

MMC/Allowance Quiz

.002


Is the allowance positive or negative?

MMC/Allowance Quiz

Positive


Is it a clearance or interference fit?

MMC/Allowance Quiz

Clearance


Arcs And Circles

  • When an arc is less than a complete circle-dimension it by radius

  • May have a definite center-e.g.. 1.00R & 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. 1.000 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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