# Reading Technical Drawings

## Presentation on theme: "Reading Technical Drawings"— Presentation transcript:

Foundations of Manufacturing

Dimensioning Systems Four different systems of dimensioning used in U.S. 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

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 3 2 7/16

Scale Reading Quiz 1 Record the scale length identified by 4 3 3/16

Scale Reading Quiz 1 Record the scale length identified by 5 3 15/16

Decimal Scales Subdivided into units of 1/10, 1/20, 1/50, or 1/100 in.
1/50 is sufficient for most applications

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 Record the scale length identified by... 1 .80

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

Scale Reading Quiz 2 Record the scale length identified by... 3 2.50

Scale Reading Quiz 2 Record the scale length identified by... 4 3.32

Scale Reading Quiz 2 Record the scale length identified by... 5 3.86

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

Decimal Rounding Quiz .11 .12 .16 .23 .44 .55 .56 .109 = .125 = .156 =
.234 = .438 = .547 = .562 = .11 .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 = 3.767 = 5.555 = 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 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 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 Record the scale length identified by 4 77.5 mm

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

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

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

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

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

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  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

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

Cylindrical Break

Short Break

Long Break

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

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? 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