Engineering Drawing BASICS

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Prepared By : Ashish Shah

Title : Engineering Drawing

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Session 1 (2 Hours)

1. Purpose…………………………………………………………………………………………………….. 3

2. Requirements of engineering drawings…………………………………………... 4

3. Sizes and layout of drawing sheets………………………………………………..5

4. Types of Engineering Drawings ………………………………………………………… 11

5. Projection Methods……………………………………………………………………………... 46

6. Multiview And Sectional View Drawings………………………………………….. 51

Session 2 (2 Hours)

7. ISO Drawing Rules…………………………………………………………………………………. 69

8. Dimensions, Symbols and Tolerances………………………………………………. 88

9. Surface Roughness………………………………………………………………………………..

99

10.Best Practices/Basic Rules…………………………………………………………………. 103

11.General Tolerances For Metric Dimensioned Products……………….104

12.Notes on Drawings…………………………………………………………………………………

106

13.Checking Drawings………………………………………………………………………………….

109

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1. Order material.

2. Plan manufacturing operations, tooling and manufacturing facilities.

3. Process material.

4. Inspect and control product quality and reliability.

5. Assemble.

6. Test.

7. Package, box and ship.

8. Determine cost.

9. Catalog.

10. Install and service.

11. Conduct final acceptance test.

12. Make alterations.

13. Record for duplication, repair or replacement.

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1. Unambiguous and clear [only one interpretation possible]

2. Complete [Provide all information for all stages of manufacture. i.e.,

detailed drawings, assembly drawings, bill of materials]3. Suitable for duplication

[Suitable scale and clarity that the drawing can be copied – even micro copied – with out losing quality]

4. Language independent [Words dependent on a language should only be used in

the title block; words should be replaced by symbols]5. Conforms to standards

[Highest standards are ISO as numerous countries learn these rules]

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• There exist standardized sheet formats for creating engineering drawings.

• American National Standard•A -8.5”x 11”•B –11”x 17”•C –17”x 22”•D –22”x 34”•E –34”x 44”

• International Standard ISO (mm)•A4 –210 x 297•A3 –297 x 420•A2 –420 x 594•A1 –594 x 841•A0 –841 x 1189

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Scale

# of Shts

Part Rev

1. Drawing Title - Description of the part or assembly.2. Drawing Number - Number of the part or assembly for archiving and cross referencing.3. Assembly Number - Number of the assembly that the part is referenced to.4. Number Off - Quantity of component or assemblies to be manufactured.5. Drawn By - Name of drawing originator.6. Scale - Identifies the main scale that the drawing is drawn in, e.g. 1:1 = full size, 1:2 = half size.7. Date - The date the drawing was created or amended on.8. Drawing Units - Units of the drawing, generally all dimensions in mm.9. Material - What the item is made of, e.g. Mild steel, Aluminium, if critical include particular grade.10. Projection System Symbol - The symbol identifying the type of projection, normally 3rd angle.11. Surface Finish – The general component surface roughness tolerance, normally 1.6microns.12. Texture – This is the components final finish e.g. anodised, painted, galvanised etc, or just clean.13. General Drawing Tolerance – General variation in size unless indicated on individual dimensions.

DIN 824

(ASME Y14.24-1999)

1. Layout Drawing

2. Monodetail Drawing

3. Multidetail Drawing

4. Assembly Drawing

5. Inseparable Assembly Drawing

6. Installation Drawing

7. Altered Item Drawing

8. Selected Item Drawing

9. Modifying Drawing

10.Arrangement Drawing

11.Control Drawings

a. Procurement Control Drawing

b. Vendor Item Control Drawing

c. Source Control Drawing

12.Envelope Drawing

13. Interface Drawing

14. Identification Cross reference Drawing

15. Mechanical Schematic Diagram

16. Electrical/Electronic Drawings

a. Functional Block Diagram

b. Single line Schematic Diagram

c. Schematic Diagram or Circuit Dia.

d. Connection Diagram

e. Interconnection Diagram

f. Logic Circuit Diagram

17. Wiring Harness Drawing

18. Cable Assembly Drawing

19. Undimensioned Drawing

20. Kit Drawing

21. Tube Bend Drawing

22. Matched Set Drawing

23. Contour Definition Drawing

24. Software Installation Drawing

25. Design Parameters Drawing

A Layout Drawing depicts new design requirements.It presents pictorial, notational, or dimensional data to the extent necessary to convey the design solution

1. Procurement Control Drawing

2. Vendor Item Control Drawing

3. Source Control Drawing

1. Functional Block Diagram

2. Single line Schematic Diagram

3. Schematic Diagram or Circuit Dia.

4. Connection Diagram

5. Interconnection Diagram

6. Logic Circuit Diagram

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Third Angle Projection for Six Principal Views First Angle Projection for Six Principal Views

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Cross-Referencing of Removed Views

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One-View Drawing

Two-View Drawing

Three-View Drawing

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A detail is used where an area needs to be enlarged in orderto illustrate a complex configuration. The scale of the detail shall be noted.

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Where the relationship between mating parts is important, the position of the related part is outlined using phantom lines.A note may be added to indicate the functional relationship of these parts.

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The cutting plane line is a heavy phantom line and can be omitted when the location is obvious.

Full Section With Cutting Plane Omitted Half Section With Cutting Plane Omitted

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The cutting plane line is always shown when the line is bent or the line has an offset.

This is called an offset section.

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Line types and thicknesses Sectioning or cross-hatching lines Leader lines Dimension lines The decimal marker Lettering, symbols and abbreviations Representation of common parts and features

Adjacent parts Flats on cylindrical or shaped surfaces Screw threads Splines and serrations Gears Springs Bearings Seals Item references and lists (BOM)

Colours

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Phantom Line Applications

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Spur-gear terms Gear conventions

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Compression springs Tension springs Torsion springs

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1. The cross-hatch lines are usually equi-spaced and, for small parts, cover the whole of the 'red' cut area.

2. They are normally positioned at 45° but if this is awkward because the part itself or a surface of it is at 45° , the hatching lines can be at another angle.

3. Logical angles like 0 °, 30 °,60 °or 90 ° are to be preferred to peculiar ones like 18 ° (say).

4. If sectioned parts are adjacent to each other, it is normal to cross hatch in different orientations (+ and -45 °) or if the same orientation is used, to use double lines or to stagger the lines.

5. If large areas are to be sectioned, there is no particular need to have the cross-hatching lines covering the whole of the component but rather the outside regions and those regions which contain details.

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Readers in the UK and USA should be aware that a full stop or point is no longer recommended as the decimal marker.

The ISO recommended decimal marker is now the comma.

Thus, taking pi as an example, it should now be written as 3,142 and not 3.142.

Similarly, the practice of using a comma as a 103 separator is no longer recommended. A space should be used instead.

Thus, one million should be represented as 1 000 000 and not 1,000,000.

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Letter Heights Drawing Size

Metric Inch Metric Inch

Drawing Title, Drawing Size Cage Code, Drawing Number and Revision Letter 6mm .24 A0, A1 D, E, F, H, J, K

(When used within the Title Block) 3mm .12 A2, A3, A4 A, B, C, G

Section and View Letters Zone Letters and Numbers in Borders 6mm .24 All All

Drawing Block Headings 2.5mm .10 All All

All Other Characters 3mm .12 All All

Minimum Letter Heights

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.375

.625.375

.625

OR

.375 .562 X 90º

.375 .562 .312

.562

.312

.375OR

Symbology is also used to define welds. The relevant standard is ISO 2553:1992.

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Colours are not normally used in engineering drawing. Indeed, in ISO 128:1982, the use of colour is 'not recommended'.

The reason for this is for the convenience of document transmission that can be more easily achieved if the colour is always black.

Hence, the standards recommend the use of the different line thicknesses and line designations such that discrimination is obtained without the use of colour.

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1. All CAPS.

2. All Decimals.

3. Select a front view that best describes the part.

4. Remove hidden lines always, unless absolutely necessary.

5. Do not duplicate dimensions. 6. Do not dimension to hidden lines.

7. Place dims between views if possible.

8. No dims allowed on body of part. Offset .38”inch from object outline.

9. Place all dims for feature in one view if possible. 10. Dim lines cannot cross dim lines.

11. Dim lines should not cross extension lines.

12. Extension lines can cross extension lines.

13. Center marks in view(s) only where feature is dimensioned only.

14. Centerlines in view(s) where feature is dimensioned.

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1. Dimensioning of features not drawn to scale 2. Chain dimensioning and auxiliary dimensioning

3. Parallel dimensioning

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4. Staggered dimensions 5. Dimensioning circles

6. Dimensioning spherical radii and diameters

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7. Dimensioning radii 8. Radii with unlocated centers

9. Radii with located centers

10. Foreshortened Radii

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11. Dimensioning chord, arc and angle 12. Fully rounded ends

13. Partially rounded ends

14. Rounded corners

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15. Coordinate or offset outline 16. Tabulated outline

17. Symmetrical outlines

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18. Round Holes19. Counterbored Holes

Counterbored Hole Example

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Arrowhead Style – The arrow styles given below illustrate the preferred style from left to right.

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Surface Texture Symbol Size and Proportion

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Lay Symbols and Their Meanings

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1.All CAPS!

2.All Decimals

3.Select a front view that best describes the part

4.Remove hidden lines unless absolutely necessary to describe the shape of the object

5.Consider datums and dimensioning scheme based on

1.Feature relationship

2.Manufacturability and inspection

3.Reduce math for machinist

6.Do not duplicate dimensions, use reference dims if necessary to duplicate

7.Do not dimension to hidden lines

8. Place dims between views if possible

9. No dims on body of part. Offset .38”inch from object outline

10. Place all dims for same feature in one view if possible

11. When multiples of the same feature exists in a view, dimension only one of the features and lable the dim as “NumberX”DIM meaning that the feature exists in that view “Number” times. For example, “4X .250”implies that in the view, there exists 4 like dimensions for the dimensioned feature

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General Tolerance – Linear Dimensions – Variations in mm per ANSI B4.3

Basic dimensions mm

0.5 to 3

Over 3 to 6

Over 6 to 30

Over 30 to 120

Over 120 to 315

Over 315 to 1000

Over 1000 to 2000

Permissible variations Fine Series ±0.05 ±0.05 ±0.1 ±0.15 ±0.2 ±0.3 ±0.5

Medium Series ±0.1 ±0.1 ±0.2 ±0.3 ±0.5 ±0.8 ±1.2

Coarse series - ±0.2 ±0.5 ±0.8 ±1.2 ±2 ±3

General Tolerance – Angles and Tapers

Length of the shorter leg, mm

Up to 10 Over 10 to 50

Over 50 to 120

Over 120 to 400

In degrees and minutes ±1° ±0° 30’ ±0° 20’ ±0° 10’

Permissible variations

In millimeters per 100 mm

±1.8 ±0.9 ±0.6 ±0.3

In milliradians ±18 ±9 ±6 ±3

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General Tolerance Note For Linear Dimensions:-

With a note: UNLESS OTHERWISE SPECIFIED, THE GENERAL TOLERANCE SPECIFIED IN ANSI B4.3 FINE SERIES APPLY. OR:-With a table: Table 2

General ToleranceUnless otherwise specified the following tolerances are applicable dimensions in mm

Linear dimensions

Over 0.5 to 6

Over 6 to 30

Over 30 to 120

Over 120 to 315

Over 315 to 1000

Over 1000 to 2000

Linear tolerance ±0.1 ±0.2 ±0.3 ±0.5 ±0.8 ±1.2

General Tolerance as a Function of Decimal Digits

Unless otherwise specified the following tolerances are applicable dimensions in mm

Linear dimensions

Up to 120

Over 120 to 315

Over 315 to 1000

Over 1000

Linear tolerance

One decimal ± No decimals ±

0.3 0.8

0.5 1.2

0.8 2

1.2 3

Specify a single tolerance value for all untoleranced nominal dimensionsby a tolerance note as follows:

UNLESS OTHERWISE SPECIFIED ALL UNTOLERANCED DIMENSIONS ARE ±0.8 mm.

(1)

(2)

(3)

(4)

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(a) Notes are headed with the word “NOTES.” Notes shall be numbered consecutively starting with number “1”. The location of notes are not specified in ASME Y14.100. Generally notes are placed in the upper Left corner reading from the top down.

(b) Notes shall be concise and grammatically correct.(c) Notes clarify features that can be more accurately defined by words rather than by delineation and dimensions.(d) Notes give instruction for applying special treatments or processes.(e) Notes give instruction to supplement non-standard symbols.(f) Notes shall be concise, in the present tense, capable of one interpretation, and parallel to the bottom edge of the drawing.(g) Do not underline or use non-standard abbreviations or acronyms.

Note: Where possible, use abbreviations and acronyms found in ASME Y14.38 Abbreviations and Acronyms, but this standard may not be available to everyone.

(h) Contractual requirements, reports or plans shall not be in the general notes.

(i) Flag note symbols , or other symbols may be used. These symbols are placed in the field of the drawing to direct you to a flag note symbol in the general notes. A statement such as “SEE NOTE 3” may be used instead of symbols.(j) Avoid non-essential words such as “the”, “a”, and “an.”

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1. DIMENSIONS ARE IN ACCORDANCE WITH ASME Y14.5M-1994.

2. INTERPRET DRAWING IN ACCORDANCE WITH ASME Y14.100.

3. REMOVE ALL BURRS AND SHARP EDGES .005 TO .015 MAX.

4. TORQUE THREADS (INSERT AMOUNT).

5. SCREW THREADS TO BE INSPECTED PER SYSTEM 21 OF FED-STD H28/20.

6. RUBBER STAMP PART NUMBER AND REV LETTER PER MIL-STD-130.

7. FINISH PER MIL-P-21415 OPER T-7.

8. ANODIZE PER MIL-A-8625, TYPE 1.

9. ALL FILLETS AND EDGES SHALL BE .010±.005 UNLESS OTHERWISE SPECIFIED.

10. MATERIAL: CRES 301 OR 302, TEMPER 1/4 FULL HARD, QQ-S-766.

11. PROTECTIVE FINISH: FINISH 5.4.1 OF MIL-STD-171.

12. SURFACE OF BALLS AND BALL RACE SHALL BE COATED WITH A FILM OR GREASE. MILG-23827.

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1. DIMENSIONS ARE IN ACCORDANCE WITH ASME Y14.5M-1994.

2. INTERPRET DRAWING IN ACCORDANCE WITH ASME Y14.100.

3. MATERIAL: AL ALY DIE CASTING. ALLOY 360.0, PER ASTM B85.

4. PART SHALL BE FREE OF ALL SPRUES, GATES, RISERS, AND FLASH.

5. UNLESS OTHERWISE SPECIFIED, CAST CORNER RADII SHALL BE .03 MAX.

6. UNLESS OTHERWISE SPECIFIED, CAST FILLET RADII SHALL BE .06 MAX.

7. UNLESS OTHERWISE SPECIFIED, WALL OR WEB THICKNESS SHALL BE .09 MAX.

8. UNLESS OTHERWISE SPECIFIED, DRAFT ANGLE SHALL BE 1° MAX. DRAFT SHALL

ADD MATERIAL TO THE DIMENSIONED FEATURES.

9. LOCATION OF EJECTOR PINS AND PARTING LINES SHALL BE AT THE SUPPLIERS DISCRETION.

10. EJECTOR PIN MARKS SHALL BE FLUSH TO .02 BELOW THE SURFACE.

11. THE AREA INDICATED SHALL BE FREE OF INDENTATIONS COLD SHUTS, MISRUNS

OR OTHER SURFACE IRREGULARITIES.

12. CASTING INSPECTION REQUIREMENTS SHALL BE PER MIL-STD-2175, CLASS 4,

GRADE D EXCEPT PENETRANT INSPECTION IS NOT REQUIRED.

13. MACHINING IS PERMISSIBLE TO MEET AS-CAST DIMENSIONAL REQUIREMENTS.

14. PART SHALL BE CLEAN AND FREE OF BURS, FINS, AND SHARP EDGES. ALL

SURFACES SHALL BE PREPARED FOR FINISHING PROCESSES.

15. UNLESS OTHERWISE SPECIFIED, MACHINE INTERNAL CORNER RADII SHALL BE .07 MAX.

16. SURFACE FINISH ON MACHINED SURFACES SHALL BE 125 MICROINCHS OR SMOOTHER.

17. SCREW THREADS TO BE INSPECTED PER SYSTEM 21 OF FED-STD H28/20.

18. THREAD REPAIR PERMISSIBLE USING INSERTS.

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Preparation for Checking the Drawing

• Non-color copies of the drawing(s) being checked. Have the CAD operator make non-color copies because colors do not print dark enough.

• Colored pencils. Use red for errors that must be corrected; blue or green for format errors that should be corrected; and yellow for crossing out what has been checked.

• All relevant component literature, e.g. bearing design data, gearbox information etc.

• Drawings of existing similar systems (hopefully ones that are working correctly).

General Items to Check

1. The drawing should be neat with bold outlines and clear hidden centerlines.

2. The checker should ensure that the drawing is unambiguous and conforms to accepted company standards.

3. The title block should be complete and the title should by clear and include the correct key words in the correct arrangement.

4. The text should be the sized in accordance with the relevant standard.

5. All elevations and sections should be structured to clearly show the shape of the items.

6. The drawings should include sufficient notes to clearly identify all production stages, and surface coatings.

7. If needed, sub-views should be used.

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Checking Dimensioning Items1. Each dimension should be clear and only able to be interpreted one way.2. Dimensions should not be duplicated. 3. Dimensions should be given between points or surfaces that have a functional relationship to each other.4. Whenever possible, dimensions should be given to finished surfaces. 5. Dimensions should be so given that it is not necessary for manufacturing to calculate, scale, or assumeany dimension.6. Dimensions should be associated with the view where the shape is best shown.7. Dimensions should be placed in the views where the dimensioned features are shown in true shape.8. Whenever possible, avoid dimensioning to hidden lines.9. Dimensions should not be placed within a view unless clearness is promoted or long extension lines areavoided.10. Dimensions that apply to two adjacent views should be placed between views.

11. Longer dimensions should be placed outside intermediate dimensions. Dimension lines should not crossextension lines.12. Do not expect manufacturing to assume a feature is centered, but give a location dimension from one side.13. Avoid a complete chain of detail dimensions; it is better to omit one dimension. Otherwise, add areference dimension in parenthesis to one detail dimension or the over-all dimension.14. Unless unavoidable, dimension lines should not cross. Extension lines may cross each other by breakingeither line.15. Leaders for notes should be straight, not curved, and pointing to the center of a circular view. 16. Leaders should extend from the beginning or end of a note.17. Dimensions for figures should be approximately centered between the arrowheads.18. Dimensions for figures should never be crowded. 19. Dimensions for angles are lettered horizontally.20. Limits dimensions have the higher amount over the lower amount.

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Engineering Drawing BASICS

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Transcript of Engineering Drawing BASICS