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Basics ofEngineering Drawing1What is Engineering Drawing?

Engineers LanguageIt is engineering language used to communicate within the engineering community to express their thoughts (designs) & get the product produced.

Why drawings are required?

To create common communication platform across the whole engineering community.Also one picture is better than 1000 words, isnt it?Part Drawings: Detail drawings completely describe a single part with multiview orthographic projections. Should provide all the information necessary to economically manufacture a high quality part.

Assembly Drawings: Assembly drawings are used to show the position and functional relationship of parts in an assembly, also via multiview orthographic projections. Generally they have no dimensions on them. Parts are 'balloon' identified and referenced to either detail drawing numbers or catalog numbers, via a Bill of Materials (BOM)

Drawing sheet sizes An A0 sheet has an area of 1m2 The sides are in the proportion 1: 2Drawing Border (or margin) The drawing should have a border of about 10 mm Space should be left for binding and hole-punching, if the drawing is to be placed in a file

Title Block and Notes Organization e.g. IES May include logo Title (Job and Drawing) Job Title (e.g. Portland Building) Drawing Title (e.g. Ground Floor Plan) Drawing Number A reference which identifies the drawing within the job and organization Revision Number Only used if changes are made to the drawing after it has been initially published Should increment with each revision (e.g. 1,2,3, or A,B,C, ) Details of each revision should be kept in Revision Table, in Notes area (see later) Issue Number Should be unique to each paper copy of the drawing that is made (may be written in by hand after printing) An Issue Book should show details of who the particular drawing was issued to, and when it was issued Scale Express as ratio drawing unit : real world unit Scales other than those above should only be used in exceptional circumstances (ensure that sensible numbers are used, e.g. 1:2500, not 1:2384) Check that the scale on the printed drawing is correct this is very important (measure it) Different parts of the drawing may be to different scales state the main scale in the Title Block, and other scales next to the relevant drawing part

Date The date of the original drawing (later revisions will have their own date noted with the details of the revision) Drawn By The name or initials of the (principal) person who created the drawing For student assignments, this should normally be your Student ID Number (HEMIS Number) Approval Signature The original drawing should be checked and approved by a competent person Later revisions have their own approval signatures (see Notes and Revisions Table) Notes A separate area, not part of the Title Block (see Location, later) Include relevant notes, e.g.: All dimensions in mm All levels in meters Do not scale off drawing if in doubt, ask May also include a key to symbols used in the drawing May include a Location Figure (a small drawing which shows the location of the main drawing relative to a larger area) Should also include a Revisions Table

Revisions Table In Notes area The table may be upside down (with column headings in the bottom row)

Location Title Block should be in the bottom right-hand corner for easy searching of required drawing in a collection of drawings Notes should be vertically above, or horizontally to the left of the Title Block (Notes are not always necessary) Folding a Drawing See extract from British Standard on the Engineering Communications unit web (BS 1192:Part 1:1984) The BS shows how to fold a drawing to ensure that the Title Block is always visible The folding method allows drawings to be placed in a ring binder file and opened for viewing without removing the drawing from the file All paper sizes from A3 to A0 are includedTitle block examples

Line fonts:

100 20Black = object line and hatchingRed = hidden lineBlue = center lineMagenta = phantom line or cutting planeGreen = DimensionCyan = Leader

Lettering:Angle of projections: First AngleIIIIIIVIViewerViewerObjectAngle of projections: Second AngleIIIIIIVIViewerViewerObjectAngle of projections: Third AngleIIIIIIVIViewerViewerObjectAngle of projections: Forth AngleIIIIIIVIViewerViewerObjectFRONTTOPRIGHT SIDEThird AngleFirst AngleAngle of projections convention:A view of an object (actual or imagined) as it would be seen by an observer who looks at the object either in a chosen direction or from a selected point of view. Pictorial sketches often are more readily made and more clearly understood than are front, top, and side views of an object. In making a pictorial drawing, the viewing direction that shows the object and its details to the best advantage is chosen. The resultant drawing is Orthographic. Orthographic Views are two-dimensional views of objects where the viewpoint of the object is at right angles to (or looking directly at) surfaces. They are used in technical and engineering drawings for accuracy.

The most commonly used pictorial drawing for technical information is called isometric drawings. Isometric drawings were developed to approximate perspective, but are much easier to draw. For a square box, all the sides are drawn as vertical lines, or at 30 degrees to the horizontal.See Fig.1

In the Isometric pictorial, the direction of its axes and all measurements along these axes are made with one scale (Fig. 1). Oblique pictorial drawings, while not true orthographic views, offer a convenient method for drawing circles and other curves in their true shape (Fig. 2).

Fig. 1Fig. 2

Engineering drawing views20ORTHOGRAPHIC VIEWS

You can also think of these views as an object inside a box with its surfaces "projecting" on to the sides of the box. You can then unfold the box to project the views on a flat surface.

Because the views are only two dimensional, more than one view is needed to completely describe the object. Usually two or three views is enough (Front, Top and Side), but often more are required.

Orthographic views21HALF VIEWS AND PARTIAL VIEWS :

Half Views and Partial views are used to simply save space when half of, or portion of a view is not needed or is redundant.

When objects are symmetrical and you are limited in the amount of space on the drawing or in drafting time, you may reduce an object image to only those features needed for minimum representation or a partial view. You may use partial views in conjunction with sectioning.

Different types of drawing viewsAUXILIARY VIEWS Auxiliary Views are used to accurately depict features on Inclined Surfaces. If there is no feature on the inclined surface, there is no need to create an auxiliary view.

Different types of drawing viewsHere are the orthographic projections for the 2 boxes. Notice that the one on the right takes up much more space that the one on the left. Notice also that the views are labeled by location, and are not related to the part of the object in the view.

Importance of choosing the Front View

Views that pictorially represent how objects and assemblies fit together are called exploded views.You may use any pictorial method including isometric projection for exploded views with isometric representation the most Common exploded views appear primarily in design presentations, catalogs, sales literature and assembly instructions. An exploded view in isometric projection Exploded Views

Sectional viewsSection views are used to get rid of the confusing hidden lines.

To produce a sectional view, an imaginary plane, called the cutting plane, cuts through the object and the two halves are separated to expose the interior construction.The direction of sight may be toward the right or left half, while you disregard the portion of the object nearest the observer. Use a cutting plane line or viewing plane line to indicate the cutting plane and the direction of sight. Sectional views may be further classified as full, half, broken-out, revolved, removed, offset, aligned sections, and partial views.

FULL SECTIONS Full section views cut all the way across the object. Full Section Views can be placed on the same page or on another page. The Cutting Plane and Arrows always are displayed.

HALF SECTIONS Half Section Views are used primarily on symmetrically shaped objects (where both halves are the same). They are a great shortcut because you can depict the inside and outside of the object all in one view. Half Section Views can be placed on the same page or on another page. If the view is displayed on another page, the Cutting Plane and Arrows always are displayed.

Full and Half sections.When it is necessary to expose only a small portion of the internal shape of an object but not enough to warrant a full or half section, use a broken-out section.Define a broken-out section with a break line or a combination of a break line and a centerline.

CONVENTIONAL BREAKS Conventional Breaks are a way of depicting a very long object without showing the entire length. It is often used for objects like rods, tubing/piping or wooden objects

Brocken-out Section

Revolved SectionsMore examplesRevolved sections are cross sections of an elongated form or object rotated toward the plane of projection to show its shape or contour. Drop a cutting plane perpendicular to the axis of the object and revolve the plane 90-degrees around a centerline and at a right angle to the axis. Retain the true shape of the revolved section regardless of the direction of the lines in the view. Superimpose the revolved section over the view and remove all original surface lines.

A removed section is a section or partial section not directly projected from the view containing the cutting plane and not revolved or turned from its normal orientation.A removed section does not align with any other view, but, sometimes appears on centerlines extended from the section cuts. Use removed sections to show small details and to facilitate dimensioning. Thisreason, they are often drawn in enlarged scale. Label removed sections alphabetically from left to right on the drawing and corresponding to the letters at the end of the cutting plane line. Precede the letters with the abbreviation SECT or SECTION. To avoid confusion, do not use the letters I, O, and Q. When you draw the removed section enlarged, indicate the larger scale beneath the section title. Removed section of an Allen wrench using: The cutting plane, and The aligned section method. Removed Sections

Aligned sections use an angled cutting plane to pass through angled features. The plane and feature are then imagined to be revolved into the original plane and the section projected from there.Aligned Sections

An offset section results when you bend the cutting plane to show internal features that are not in a straight line. The offsets or bends in the cutting plane never show in the sectional view. Cutting plane lines in an offset section appear as thick, dashed lines. Offset SectionsCross Hatch SymbolsCast Iron (General Use)White Metal (Zinc)SandSteelMagnesium, AluminumTitaniumMarble, Slate, Glass, etc.Water, LiquidsWood; Cross GrainWith GrainFelt, Leather, & FiberBronze, Brass, etc.ConcreteSurface finish

Ra Value v/s conventional symbols:

Direction of lay:

Requirement for machining Machining Allowance

The Symbol indicates the surface finish requirements and shows a machining allowance requirement of 3mm on all surfaces.

Symbol for surface texture all component surfaces

The Symbol indicates that all of the component surfaces are to be machined... Location of Surface Texture Symbols

The shows typical locations for surface texture symbols...

Roughness Average Micrometers m (Micro inches in.)Surface roughness produced by common production processes

Roughness Average Micrometers m (Micro inches in.)Surface roughness produced by common production processes

Welding symbol

The collective process of modeling, defining and describing geometric sizes and feature relationships, and providing all of the required technical information necessary to produce and inspect the part is called dimensioning and Tolerancing.The current National Standard for dimensioning and Tolerancing in the United States is ASME Y14.5M - 1994.Coordinate Dimensioning and ToleranceDrawing NotesDRAWN IN ACCORDANCE WITH ASME Y14.5M - 1994REMOVE ALL BURRS AND SHARP EDGES ALL FILLETS AND ROUNDS R .06 UNLESS OTHERWISE SPECIFIEDNotes should be concise and specific. They should use appropriate technical language, and be complete and accurate in every detail. They should be authored in such a way as to have only one possible interpretation.General NotesLocal Notes4X 8.20

M10 X 1.25

82 CSK 10

1.5 X 45 CHAMArrowheads200R 8.51st2nd3rd4thOf the four different arrowhead types that are authorized by the national standard, ASME Y14.2M 1994, a filled arrowhead is the highest preference.Arrowheads are used as terminators on dimension lines. The points of the arrowheads on leader lines and dimension lines must make contact with the feature object line or extension lines which represent the feature being dimensioned. The standard size ratio for all arrowheads on mechanical drawings is 3:1 (length to width).There should be a visible gap (~1.5 mm) between the object lines and the beginning of each extension line.Extension lines overlap dimension lines (beyond the point of the arrowheads) by a distance of roughly 2-3mm1.751.06Dimension Lines and Extension LinesDimensions should be placed outside the actual part outline. Dimensions should not be placed within the part boundaries unless greater clarity would result.Arrows in / dimension in Arrows out / dimension inArrows in / dimension outArrows out / dimension out2.5621.250.750.500Placement of Linear Dimensions Order of PreferenceWhen there is not enough room between the extension lines to accommodate either the dimension value or the dimension lines they can be placed outside the extension lines as shown in the fourth exampleTypes of Dimensioning: Parallel Dimensioning:Parallel dimensioning consists of several dimensions originating from one projection line.

Superimposed Running Dimensions:Superimposed running dimensioning simplifies parallel dimensions in order to reduce the space used on a drawing. The common origin for the dimension lines is indicated by a small circle at the intersection of the first dimension and the projection line. In general all other dimension lines are broken.The dimension note can appear above the dimension line or in-line with the projection line.

Dimensioning Chain Dimensioning:Chains of dimension should only be used if the function of the object won't be affected by the accumulation of the tolerances. (A tolerance is an indication of the accuracy the product has to be made to. Tolerance will be covered later in this chapter).

Combined Dimensions:A combined dimension uses both chain and parallel dimensioning.

Dimensioning by Co-ordinates:Two sets of superimposed running dimensions running at right angles can be used with any features which need their centre points defined, such as holes.

Simplified dimensioning by co-ordinates:It is also possible to simplify co-ordinate dimensions by using a table to identify features and positions.

Each dimension shall have a tolerance, except for those dimensions specifically identified as reference, maximum, minimum, or stock (commercial stock size). The tolerance may be applied directly to the dimension (or indirectly in the case of basic dimensions), indicated by a general note, or located in a supplementary block of the drawing format

Dimensioning and tolerance shall be complete so there is full understanding of the characteristics of each feature. Neither scaling (measuring the size of a feature directly from an engineering drawing) nor assumption of a distance or size is permitted

Each necessary dimension of an end product shall be shown. No more dimensions than those necessary for complete definition shall be given. The use of reference dimensions on a drawing should be minimized

Dimensions shall be selected and arranged to suit the function and mating relationship of a part and shall not be subject to more than one interpretation

The drawing should define a part without specifying manufacturing methods

Dimensions should be arranged to provide required information for optimum readability. Dimensions should be shown in true profile views and refer to visible outlinesFundamental rules of dimensioningWires, cables, sheets, rods, and other materials manufactured to gage or code numbers shall be specified by linear dimensions indicating the diameter or thickness. Gage or code numbers may be shown in parentheses following the dimension

A 90o angle applies where center lines and lines depicting features are shown on a drawing at right angles and no angle is specified

Unless otherwise specified, all dimensions are applicable at 20C (68F). compensation may be made for measurements made at other temperatures

All dimensions and tolerances apply in a free state condition. This principle does not apply to non-rigid partsReference Dimension Symbol (X.XXX)Reference dimensions are used on drawings to provide support information only. They are values that have been derived from other dimensions and therefore should not be used for calculation, production or inspection of parts.

The use of reference dimensions on drawings should be minimized.2.2501.000(.750).5001.250.500(.750).500Reference Dimensions4.3751.2501.4381.062.6881.0001.8752.312.375 (10mm) Minimum Spacing.250 (6mm) Minimum SpacingShorter (intermediate) dimensions are placed closest to the outline of the part, followed by dimensions of greater length. Dimensions nearest the object outline should be at least .375 inches (10 mm) away from the object, and succeeding parallel dimension lines should be at least .250 inches (6 mm) apart.Location of DimensionsDimensions should be placed outside the actual part outline 4.3751.062.6881.0001.8752.3121.2501.438Extension lines should not cross dimension lines if avoidableBETTERBasic Dimensioning Good PracticeIn-line dimensions can share arrowheads with contiguous dimensions4.3751.062.6881.0002.3121.2501.4381.8751.3751.375.625 THRU.250.62.250 x .62 DPDiameter Dimensions Holes and cutoutsWhenever it is practical to do so, external diameters are dimensioned in rectangular (or longitudinal) views. Cylindrical holes, slotted holes, and cutouts that are irregular in shape would normally be dimensioned in views where their true geometric shape is shown..751.252.00.25 THRUShafts and HolesDiameter Dimensions1818181818183.50.8753X .5626X .188Placement with Polar CoordinatesTo dimension features on a round or axis symmetric component To indicate the size of fillets, rounds, and radiiR.562R.750R.312R.312R14.25Radial Dimensions To indicate the size of angular details appearing as either angular or linear dimensions.

922 x 4563AlternateAngular DimensionsTimes and By Symbol: XThe X symbol can also be used to indicate the word by. For instance, when a slot that has a given width by a specified length, or a chamfer that has equal sides (.12 X .12). When used to imply the word by, a space must precede and follow the X symbol.If the same feature is repeated on the drawing (such as 8 holes of the same diameter and in a specified pattern), the number of times the instruction applies is called out using the symbol X. .12 X 45CHAMFER.375 .562 X 82CSK8X .250 THRU Normally specified by diameter and depth (or THRU note used). Specify reaming if accuracy/finish is important.Drilled Holes259012.5 2x 12 THRU 1212.5 14 THRU

124525905032Depth or Deep Symbol** This symbol is currently not used in the ISO standard. It has been proposed..375.625EXAMPLE.375.625ORASME/ANSI Hole Depth SymbolFeatures such as blind holes and counterbores, must have a depth called out to fully describe their geometry. Countersink Symbol*ASME/ANSI Countersink SymbolThe symbol denotes a requirement for countersunk holes used to recess flathead screws. The height of the symbol is equal to the letter height on the drawing, and the included angle is drawn at 90. Note that this symbol is not used in the ISO (international) standard.* This symbol is currently not used in the ISO standard. It has been proposed..375 .562 X 90EXAMPLECounterbore Symbol*ASME/ANSI Counter bore SymbolThis symbol denotes counterbored holes used to recess machine screw heads. * This symbol is currently not used in the ISO standard. It has been proposed.EXAMPLE.375 .562 .312.562.312.375ORCounter bores and Countersinks ISO StandardFlat Head

Socket Cap Head or Machine screws2 x

8.8 THRU 14 C BORE x 8.2 DP122 x

1250259012.53250259012.532 8.8 THRU 15 C SUNK X 90 ISO specify metric only:Note: Use standard screw sizes onlyM 16 x 2 - 4h - 5HISO metric designationNominal Diameter(mm)Thread Pitch(mm) Class of fit of this thread(optional)Class of fit of mating thread (optional)American Unified Threads:

3/4 - 10 - UNC - 2ANominal Diameter(inches)Threads per inchClass of fit (optional)

Thread SeriesUNC = Unified CoarseUNF = Unified FineThread Type (optional)A=ExternalB=InternalScrew Threads

M 16 x 23/4 - 10 - UNCThreads and Screw FasteningExample Assembly

Threads and Screw Fastening (cont.)

Base Detail Threads and Screw Fastening (cont.)LidDetail'A''A'Section 'A'-'A'3 Holes

12.7 THRU

EQ SP on 120 PD

Dimensioning strategy:Break up into simple shapesDimension each simple shape (size)Dimension position of each shape (location)Check for redundant dimensionsDo in rough form firstPlan for positioning of dimensions on final drawingSize one featureSize all features

Locate one featureLocate all features

Dos & Donts of dimensioning:

Tolerancesimportant to interchangeability and provision for replacement parts It is impossible to make parts to an exact size. The tolerance, or accuracy required, will depend on the function of the part and the particular feature being dimensioned. Therefore, the range of permissible size, or tolerance, must be specified for all dimensions on a drawing, by the designer/draftsperson.

Nominal Size: is the size used for general identification, not the exact size.

Actual Size: is the measured dimension. A shaft of nominal diameter 10 mm may be measured to be an actual size of 9.975 mm.

General Tolerances: In ISO metric, general tolerances are specified in a note, usually in the title block, typically of the form: "General tolerances .25 unless otherwise stated".

In English Units , the decimal place indicates the general tolerance given in the title block notes, typically:Fractions = 1/16, .XX = .01, .XXX = .005, .XXXX = 0.0005,

Note: Fractions and this type of general Tolerancing is not permissible in ISO metric standards.

Specific Tolerances indicate a special situation that cannot be covered by the general tolerance.

Specific tolerances are placed on the drawing with the dimension and have traditionally been expressed in a number of ways:Specific Tolerances40+0.05- 0.0340.01 +0.0440.0539.97 Bilateral ToleranceUnilateral ToleranceLimit DimensionsLimits are the maximum and minimum sizes permitted by the the tolerance. All of the above methods show that the dimension has:a Lower Limit = 39.97 mman Upper Limit = 40.05 mma Tolerance = 0.08 mm

Manufacturing must ensure that the dimensions are kept within the limits specified. Design must not over specify as tolerances have an exponential affect on cost.Assembly Drawings: The assembly /sub-assembly drawings are drawings of discrete sub-systems showing in some detail how the component items fit together. Typical assembly drawings include gearbox drawings, roller drawings, guard system drawings.

Typical assembly drawing contains the following; At least three orthographic views with sections as needed to clearly show all of the details and their relative positions. Overall and detail dimensions The weight/mass of the assembly/sub-assembly will be noted. A parts list identifying all of the component details with quantities and materials and supply details. A list of reference drawings and notes identifying the relevant codes and specifications and testing requirements. Include a note explaining the required assembly operation and give the dimensions for the alignment or location of the pieces. An assembly drawing should not be overloaded with detail. Include reference letters and numbers representing the different parts. These part numbers usually enclosed by circles with a leader pointing to the piece.Assembly Drawing77 A unit assembly (subassembly) is a drawing of a related group of parts and used to show the assembly of complicated machinery for which it would be practically impossible to show all the features on one drawing. To illustrate; headstock, tailstock, and gearbox unit assemblies should be included in the drawing of a lathe.

An outline assembly is used to describe the exterior shape of a machine or structure, so it contains only the primary dimensions. If it is made for catalogs or illustrative purposes, dimensions are often omitted. They are also called as installation drawings.

An assembly working drawing includes all the necessary information for producing a machine or structure on one drawing. This requires providing adequate orthographic views together with dimensions.

A diagram drawing is an assembly showing ,symbolically, installation of equipment and often made in pictorial form.

The bill of material is a tabulated list placed either on the assembly drawing or on a separate sheet. The list gives the part numbers, names, quantities, material and sometimes stock sizes of raw material, detail drawing number, etc. The term "bill of material" is usually used in structural and architectural drawing whereas the term "part list" is used in machine-drawing practice.Assembly Drawing78Assembly Drawing

79Assembly Drawing

80Features of an Assembly DrawingDimensionsDetailed dimensions required for manufacture are excluded from assembly drawings. But overall dimensions of the assembled object are usually indicated.If the spatial relationship between parts if important for the product to function correctly then these should also be indicated on the drawing. For example indicating the maximum and minimum clearance between two parts.

Internal PartsIf there are internal assemblies, sectional views should be used.

Parts listEach part is given a unique number, indicated on the drawing by a circle with the number in it and a leader line pointing to the part. The leader line terminates in an arrow if the line touches the edge of the component, or in a circle if the line terminates inside the part.A table of parts should be added to the drawing to identify each part, an example of a parts list is shown below:The first three items; Item No., Description, and Quantity should be completed for every distinct part on your drawing. (i.e. the number of duplicate parts are recorded in the quantity). The material is used for components that are being made within the company. The Remarks column is useful for specifying a manufacturers part number when using bought-in parts.Item No.DescriptionQtyMaterialRemarks81Exploded DrawingAn exploded view is a representative picture or diagram that shows the components of an object slightly separated by distance, or suspended in surrounding space in the case of a three-dimensional exploded diagram, as if there had been a small controlled explosion emanating from the middle of the object which separated all of the parts of that object an equal distance away from their original locations.Exploded diagrams are common in descriptive manuals showing parts placement, or parts contained in an assembly or sub-assembly. Usually such diagrams have the part identification number and a label indicating which part fills the particular position in the diagram. Many spreadsheet applications can automatically create exploded diagrams, such as exploded pie charts.

82Exploded Drawing

83Drawing for sheet metal parts

Typical sheet metal parts contain one form view, flat view, Isometric view and other necessary views.Form view: This view represents details in the bent or form conditionFlat view: This view represents details of blank development along with the necessary holes and cut featuresIsometric view: This view represents about 3D image of the sheet metal part

Formed ViewFlat ViewIsometric View84Drawing for forging parts

ForgingForging is the working of metal by plastic deformation. It is distinguished from machining, the shaping of metal by removing material, such as by drilling, sawing, milling, turning or grinding, and from casting, wherein metal in its molten state is poured into a mold, whose form it retains on solidifying. The processes of raising, sinking, rolling, swaging, drawing and upsetting are essentially forging operations although they are not commonly so called because of the special techniques and tooling they require.Forging results in metal that is stronger than cast or machined metal parts. This is because during forging the metal's grain flow changes into the shape of the part, making it stronger. Some modern parts require a specific grain flow to ensure the strength and reliability of the part.85Drawing for casting parts

86Engineering Standards Introduction to standards Standards Organizations Knowledge of some International Standards Examples of StandardsWhat are standards?Just like any other language, the grammar of this engineering language is defined by various standards across globe. These standards talk about dimension styles, tolerance, sheet sizes, etc. In short these standards define each & every thing required to create any basic engineering drawing

History and Evolution of Standards The industrial revolution in 19th century forced the world to create the standards for drawing creation. Mainly it started with military application. Then it was adapted by all other industries. Almost every nation has its own standards.

Usage of standardsThese standards are used in all engineering streams, Mechanical, Civil, Chemical, Automobile, electronics, etc

Types of standardsDrawing standards, welding standards, safety standards, construction standards, etc Introduction to standardsStandards Organizations Standards Developing Organizations (SDOs)All over the world there are number of organizations which are involved in developing different standards.

ASME: American Society of Mechanical Engineers ANSI: American National Standards Institute BIS: Bureau of Indian Standards BSI: British standards DIN: Deutsches Institute for Norms JIS: Japanese Industrial Standards

Scope of work Creating standards Standards publication Training about standards Assessment & certification Product testingStandards development process Identifying the requirements Creating a draft copy of the standard Deliberation by authorized panel Establishment of the standard Promotion of the standardsKnowledge of some International Standards ASTM: AMERICAN STANDARDS FOR TESTINGASTM provides standard for ferrous-non-ferrous materials specification & material testing. Used in US.

API: AMERICANPETROLEUMINSTITUTIONWidely followed by petrochemical industry & Chemical industry

ASME: AMERICAN SOCIETY OF MECHANICAL ENGINEERSASME provides codes and standards for various mechanical elements. Pressure vessel codes by ASME are used by all industrial nations.

AIAA: AEROSPACE INDUSTRIES ASSOCIATION OF AMERICAThis standards service includes National Aerospace Standards (NAS) and metric standards (NA Series)

BSI: BRITISH STANDARDS INSTITUTIONBritish standards provide standards for various machine elements, material specification and testing, sealants and automotive componentsDIN standards:Standards by Germany widely followed across Europe Japan and America. JIS: JAPANESE INDUSTRIAL STANDARDSProvides standards and codes for almost all major engineering divisions.

ISO: INTERNATIONAL STANDARDS ORGANIZATION

BIS: BUREAU OF INDIAN STANDARDS

SAE: SOCIETY OF AUTOMOTIVE ENGINEERSProvides standards for Aerospace, Off-highway vehicles and automobile components design. Knowledge of some International Standards GD&T Standards Drawings and Terminology Measurement standards Tooling Standards Welding standards Refrigeration and Air Conditioning Standards Hydraulics Standards Aerospace Standards Manufacturing standards Automobile StandardsExamples of StandardsTHANK YOUDos & Donts of dimensioning a drawing

1. Each dimension should be given clearly, so that it can be interpreted in only one way.

2. Dimension should not be duplicated or the same information be given in two different ways, dual dimensioning excluded, and no dimensions should be given except those needed to produce or inspect the part.

3. Dimensions should be given between points or surfaces that have a functional relation to each other or that control the location of mating parts.

4. Dimensions should be given to finished surfaces or important center lines in preference to rough surfaces wherever possible.

5. Dimensions should be so given that it will not be necessary for the machinist to calculate, scale, or assume any dimension.

6. Dimensions should be attached to the view where the shape is best shown (contour rule).

7. Dimensions should be placed in the views where the features dimensioned are shown true shape.

8. Avoid dimensioning to hidden lines wherever possible.

9. Dimensions should not be placed upon a view unless clearness is promoted and long extension lines are avoided.

10. Dimensions applying to two adjacent views should be placed between views unless clearness is promoted by placing some of them outside.

11. The longer dimensions should be placed outside all intermediate dimensions, so that dimension lines will not cross extension lines.

12. DO not expect the workman to assume a feature is centered (as a hole on a plate), but give a location dimension from one side. However, if a hole is to be centered on a symmetrical rough casting, mark the center line and omit the locating dimension from the center line.

13. A dimension should be attached to only one view (extension lines not connecting two views).

14. Detail dimensions should "line up" in chain fashion.

15. Dimension lines should be spaced uniformly throughout the drawing. They should be at least 10mm from the object outline and 6mm apart.

16. No line of the drawing should be used as a dimension line or coincide with a dimension line.

17. Dimension lines and extension lines should not cross, if avoidable (extension lines may cross each other).

18. A center line may be extended and used as an extension line, in which case it is still drawn like a center line.

19. Center lines should generally not extend from view to view.

20. Leaders for notes should be straight, not curved, and pointing to the center of circular views of holes wherever possible.

21. Leaders should slope at 450, or 300, or 600 with horizontal but may be made at any convenient angle except vertical or horizontal.

22. Notes should always be lettered horizontally on the sheet.

23. Notes should be brief and clear, and the wording should be standard in form.

24. Finish marks should be placed on the edge views of all finished surfaces, including hidden edges and the contour and circular views of cylindrical surfaces.

25. Finish marks should be omitted on holes or other features where a note specifies a machining operation.

26. Finish marks should be omitted on parts made from rolled stock.

27. If a part is finished all over, omit all finish marks, and use the general note: FINISH ALL OVER, or FAO, not "f"AO or "f"ALL OVER.

28. A cylinder is dimensioned by giving both its diameter and length in the rectangular view, except when notes are used for holes. A diagonal diameter in the circular view may be used in cases where clearness is gained thereby.

29. Holes to be bored, drilled, reamed, etc., are size-dimensioned by notes in which the leaders preferably point toward the center of the circular views of the holes. Indications of shop processes may be omitted from notes.

30. In general, a circle is dimensioned by its diameter, an arc by its radius.

31. The letter R should always follow a radius dimension figure. The radial dimension line should have only one arrowhead, and it should pass through or point through the arc center and touch the arc.

32. Cylinders should be located by their center lines.

33. Cylinders should be located by coordinate dimensions in preference to angular dimensions where accuracy is important.

34. When there are several rough non-critical features obviously the same size (fillets, rounds, ribs, etc.), it is necessary to give only typical dimensions, or to use a note.

35. When a dimension is not to scale, it should be underscored with a wavy line or marked NTS or NOT TO SCALE.

36. Mating dimensions should be given correspondingly on drawings of mating parts.

37. Decimal dimensions should be used when accuracy greater than 1/64" is required on a machine dimension.

38. Avoid cumulative tolerances, especially in limit dimensioning.