Lecture notes Engineering Drawing

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Textbook for Vocational Training − Engineering Drawing MetalTable of Contents Textbook for Vocational Training − Engineering Drawing Metal..................................................................1 Preliminary remarks................................................................................................................................1 1. Introduction into Engineering Drawing................................................................................................2 1.1. Tasks and Importance of Engineering Drawings......................................................................2 1.2. Types of Drawings....................................................................................................................5 1.3. The Drawing Sheet.................................................................................................................11 1.4. Lettering of Drawings..............................................................................................................21 1.5. Types of Lines and Groups of Lines.......................................................................................35 1.6. Scales.....................................................................................................................................38 1.7. Basic Geometric Constructions...............................................................................................39 2. Perspective Representation of Simple Workpieces..........................................................................53 2.1. Preliminary Remarks...............................................................................................................53 2.2. Standardised Perspectives (Projections)................................................................................54 2.3. Dimensioning of Perspective Workpieces...............................................................................56 2.4. Perspective Representation of a Circle (Fig. 2.8.)..................................................................58 2.5. Principles of the Perspective Representation of Simple Workpieces......................................59 2.6. Representation of Workpieces in Perspective from Different Station Points...........................60 3. Representation of Workpieces in Right−angle Parallel Projection...................................................61 3.1. Development and Number of Views........................................................................................61 3.2. Representation of Flat Workpieces in a View.........................................................................65 3.3. Representation of Workpieces in Two Views..........................................................................68 3.4. Representation of Workpieces in Three Views.......................................................................72 3.5. Representation of Workpieces in More Than Three Views.....................................................76 3.6. Workpiece Position.................................................................................................................77 4. Representation and Dimensioning of Simple Workpieces with Prismatic and Cylindrical Basic Shape..................................................................................................................................................80 4.1. Basic Elements of Dimensioning.............................................................................................80 4.2. Special Elements of Dimensioning..........................................................................................86 4.3. Entering Dimensions in Drawings...........................................................................................98 4.4. Dimensional Variations I.......................................................................................................108 5. Sectional Views..............................................................................................................................114 5.1. Introduction into the Process of Drawing Sectional Views....................................................114 5.2. Full Sectional Views..............................................................................................................121 5.3. Half Sections.........................................................................................................................130 5.4. Parts in the Cutting Plane Which are not Cut........................................................................133 6. Thread Representation and Thread Dimensioning.........................................................................136 6.1. Thread Representation.........................................................................................................137 6.2. Thread Dimensioning............................................................................................................140 6.3. Representation of Screwed Parts.........................................................................................144 6.4. Bolts and Nuts.......................................................................................................................145 7. Surface Finish Harks and Production Specifications......................................................................149 7.1. General Remarks..................................................................................................................149 7.2. Marking of Shaped Surfaces.................................................................................................150 7.3. Marking of Treated Surfaces.................................................................................................162 8. Dimensional Variations II................................................................................................................164 8.1. Importance and Necessity of the Determination of Suitable Tolerances..............................164 8.2. Determination of Tolerances by Symbols Designating Fits...................................................165 8.3. Fits........................................................................................................................................180 9. Representation of Assembled Parts...............................................................................................189 9.1. General Application...............................................................................................................189 9.2. List of Parts...........................................................................................................................196 9.3. Examples..............................................................................................................................199 10. Intersections and Developments..................................................................................................203 10.1. Fundamentals.....................................................................................................................203 10.2. Intersection..........................................................................................................................207 10.3. Developments.....................................................................................................................220 11. Gear Elements and Gear Diagrams.............................................................................................225 11.1. Symbolic Representation of Gear Elements.......................................................................225 11.2. Belt Drive.............................................................................................................................234 11.3. Friction−gear Drive..............................................................................................................235 iTable of Contents Textbook for Vocational Training − Engineering Drawing Metal 11.4. Toothed−wheel Gearing......................................................................................................236 11.5. Summary.............................................................................................................................241 11.6. Reading and Representation of Simple Gear Diagrams.....................................................242 12. Structural Steel Elements.............................................................................................................244 12.1. Sections..............................................................................................................................244 12.2. Joining and Types of Joints.................................................................................................250 12.3. Examples of Structural Units and Design Problems in Steel Construction.........................264 12.4. Drawings in Steel Construction...........................................................................................277 13. Fittings and Piping........................................................................................................................281 13.1. Importance..........................................................................................................................281 13.2. Pipe Fittings........................................................................................................................281 13.3. Symbols for Pipe Lines.......................................................................................................286 13.4. Sanitary Details...................................................................................................................292 Problem sheets No. 1 to 52 (appendix)..............................................................................................298 iiTextbook for Vocational Training − Engineering Drawing Metal CRYSTAL Lehr− und Lernmittel, Informationen, Beratung Educational Aids Literature, Consulting Moyens didactiques, Informations, Service−conseil Material didáctico, Informaciones, Asesoría Textbook For Vocational Training Feedback: IBE e.V. 90−34−0104/2 Deutsche Gesellschaft für Technische Zusammenarbeit (GTZ) GmbH Institut für berufliche Entwicklung e.V. Berlin Original title: “Technisches Zeichnen − Metall” Authors: Walter Jüdecke Peter Kallmeyer Dr. Horst Kummer Dr. Walter Obst H.−J. Rosenbauer First edition © IBE Institut für berufliche Entwicklung e.V. Parkstraße 23 13187 Berlin Order No.: 90−34−0104/2 Preliminary remarks The Textbook Engineering Drawing − Metal − is intended for all trainees of metal−working trades. Due to the consistent consideration of the unit of theory and practice, the trainee can use it as a guide during theoretical instructions and in practical vocational training. The grasping of the problems dealt with is facilitated by numerous illustrations and a vivid representation of the subject−matter in a way that is easily understandable. 1Each Chapter contains a number of problems and questions for repetition. They are concentrated on the focal points of the subjects of particular importance to metal−working trades and the trainee can take advantage of them for checking his knowledge independently. In order that the acquisition of knowledge by the trainee can be successfully assisted by the process of practising, the author has prepared problem sheets for each Chapter which are compiled in an Appendix to the book. Institut für berufliche Entwicklung 1. Introduction into Engineering Drawing 1.1. Tasks and Importance of Engineering Drawings In any engineering drawing, information of different kinds are stored. Engineering drawing is a graphic language that expresses and conveys ideas enabling the perceiving, understanding and production of technical objects. This shows that the engineering drawing is an important means of communication between men, men and machines and between machines. Today, in all trades and professions, in leisure time and in households, more and more devices, machines and plants are used which are described and operated on the basis of engineering drawings. In textbooks, periodicals and other publications, engineering drawings also play an important part. For the manufacture of products, engineering drawings have become an indispensable means which actually enables production. For this reason, the subject of “Engineering Drawing” has become part and parcel of vocational training. That is why it has become a necessity to teach the fundamentals of this subject already in elementary schools. The engineering drawing has a twofold importance: It is necessary for the user of technical objects in order to carry out operation, maintenance and, to a limited extent, repairs. This is the general importance of the engineering drawing. It is necessary for the manufacturer of technical objects in order to be in a position to produce them manually and mechanically. This is the special importance of the engineering drawing. In the various chapters of the present textbook, one enters into particulars especially of this special importance which consists in the fact the expert worker of metal−working and metal−processing trades also needs the engineering drawing to be in a position to produce. This shows that the drawing is turned into a manufacturing programme or production order. In order to meet the requirements of this task, the engineering drawing must contain the data which are shown in Fig. 1.1 and are related to the object of work. In addition it can give information about design and function of the workpiece to be made, of the device and structure or the main component, machine or plant to be produced. The extent of the required data will be determined by the intended use of an engineering drawing. 2Fig. 1.1. Engineering drawing as a means of communication It is the task of an engineering drawing to be information store for technical and graphic data and thus to become a means of communication between designer, draughtsman, expert worker and user (see Fig. 1.2). 3Fig. 1.2. The engineering drawing as the work order In the form of a draft, a production order, an operating instruction or directions for use, the engineering drawing is always an important technical document without which production planning, preparation and carrying−out as well as organisation and sale of the production would be unthinkable. In order to meet the requirements of a means of communication, the preparation of engineering drawings must be effected according to standardised or uniform rules. These rules are called standards which represent best solutions which are recommended or made compulsory for the territorial regions in question so that they adopt legal character. For the preparation, carrying−out and checking as well as for teh revision of standards, state institutions are responsible. Today, more and more international unifications are accepted in addition to national standards. These unifications or standards enable a specialisation and cooperation of production and, thus, are instrumental in the promotion and consolidation of the economic relations between countries. Standards are classified in three main groups (see Fig. 1.3): according to their contents, according to the binding force stated (degree of obligatory conditions) and according to their scope. 4Fig. 1.3. Classification of standards Condition standards are concerned with dimension, material specifications, surfaces of a product. Methods standards standardise, for example, manufacturing and testing procedures and storage specification for a product. Communication standards are prepared in order to standardise, for example, terms and symbols. Symbols play an important part because they facilitate communication on an international level in a much better way than verbal statements. The development of international standards, especially for engineering drawing, is on the increase. For the CMEA−states (CMEA = Council for Mutual Economic Aid), the “Uniform System of Design Documentation” has been created which has supported the socialist economic integration with particular respect to a rationalisation of the preparation, keeping and reproduction of design documents. Standards valid so far have been and will be checked and revised and, provided with comprehensive explanations, introduced into the economies of several countries according to a new systematic representation. 1.2. Types of Drawings The great number of existing and the continuously increasing number of engineering drawings call for a consistent grouping and coordination of them. The term “engineering drawing” today has become a collective name under which various types of engineering drawings should be subsumed according to agreed criteria. Fig. 1.4. shows a compilation of the usual distinctive features. 5Fig. 1.4. Distinctive features of engineering drawings 1.2.1. Distinction according to General Principles The sketch Frequently, sketches are necessary for the preparation of a drawing. In a sketch, first considerations about shape, dimension or function of a technical object are laid down. Further, sketches are a suitable form to give explanations related to the overall drawing so that sketching may be necessary after the drawing. It is also possible to use a sketch as an “aid to memory” in order to acquire technical interrelations and shapes or dimensions as information so that this can be used later (see also Fig. 1.5). Fig. 1.5. Importance of the sketch − Usually, a sketch is prepared offhand. − In sketching, specified basic standards and ratios of size or proportions must be observed although the sketch need not be drawn to scale. − To facilitate sketching, frequently chequered drawing paper is used. The drawing 6The drawing is the representation of an object (workpiece, tool, plant, building, component layout, etc.) true to scale. Its preparation calls for comprehensive knowledge of the relevant standards and their use and for a developed imaginative faculty enabling the designer to picture a technical object which always has three dimensions (length, width, thickness) but will be represented in two dimensions only. − A drawing is prepared with the help of drawing equipment (e.g. straight edge, compass, curve). − For the proportions, a scale must be specified. − The drawing must conform to accepted standards. The plan Plans as generally differentiated from engineering drawings are representations which specify the position of objects or their function. Here are three examples: − The track plan as a survey of a railway trackage (see Fig. 1.6). − They layout plan or site plan showing the arrangement of machines in a hall (see Fig. 1.7). − The plan of a network of pipes giving a survey of installed pipe lines (see Fig. 1.8). Fig. 1.6. Track plan 1 Bumping post, 2 Simple switch, 3 Double−slip points, 4 Railway balance, 5 Loading station 7Fig. 1.7. Layout plan 8Fig. 1.8. Plan of a network of pipes 1 Crossing of lines, 2 Shut−off valve, 3 Water counter equipment, 4 Fountain, 5 Garden hydrant, 6 Underground hydrant 7 Overground hydrant 1.2.2. Distinction according to the Preparation When a drawing or sketch is made for the first time, then it is an original. For the preparation, a lead pencil, fibre pencil or ink can be used. Originals are kept particularly carefully and are subjected to certain safety regulations. In most cases, in practice the original is not used but a copy. The reproduction of copies is effected either according to the heliographic printing process or the photographic process. Copies can also be produced by printing. The most widely known method of reproducing engineering drawings is the heliographic printing process. In this process, the original drawing, which must be on transparent paper, is placed on light−sensitive tracing paper and exposed to a light source of high intensity. The light destroys the light−sensitive film while the outlines, lines and signs which were drawn on the original remain. In a dry process, ammonia vapours, to which the exposed tracing is subjected, are instrumental in developing and copying. Besides the heliographic printing process, photographing should be mentioned which gains in importance especially in association with technical modeling. The xerographic process, in which opaque paper can be used for the original, is subsumed under the heading of the photographic process. Examples of the conventional printing process are the stencil printing, the small offset printing and the embossed printing processes which will not be explained in detail here. Fig. 1.9 gives a survey of the reproduction of originals of drawings differentiated according to the kind of process of reproduction used. 9Fig. 1.9. Original drawing and copy 1.2.3. Distinction according to the Content An overall drawing is given when a machine, a plant, a device or a structure is represented in the assembled state. This definition also includes representations of complete processes and plans. It is common practice to number the overall drawings with consecutive numbers which are also allotted to the individual components or objects (see also Fig. 1.19.2). A group drawing is defined as a representation of a sub−assembly or a main component which is part of finished product and which is composed of two or more parts. The group drawing contains details of assembling and of the type of connection between the individual parts. Individual parts are represented in a detail drawing. This form of a drawing contains data of size and shape and gives information about working and machining. It is the basis of the manufacture and checking of the technical object to be made and, therefore, must be concise and subject to but one. Interpretation. The dimensions must conform to the sequence of operations in manufacture (see Fig. 1.19.3). Sometimes it is necessary to prepare a representation of the interaction of individual elements which is defined as a schematic representation. In this representation, the individual parts are shown in a simplified (schematic) form. It includes, for example, gearing layouts and plans for the characterisation of a power flow. 1.2.4. Distinction according to the Purpose The intended use determines the type, the contents and the preparation of an engineering drawing. A distinction is made between: − Draft drawings and design drawings which are required for the preparation of production, for calculating and as a basis for planning. − Manufacturing drawings as a basis for the production of a product. − Operating instructions, maintenance and repair plans which facilitate the proper use, care and repair of technical objects. If the drawing is intended for explanations for the user, particularly vivid and clear illustrations have to be presented. 10Further examples are order drawings (for explanations regarding the order, for inquiries and complaints), approval, foundation, packing, forwarding and revision drawings. The latter must be provided with the dimensions important for revision (acceptance). These examples do not constitute the full list of drawings. Repetition 1. What is the special importance of an engineering drawing? 2. Explain the term “standard”. 3. Determine the difference between condition standards, methods standards and communication standards. 4. What is the difference between a drawing and a sketch? 5. Declare the possibilities for reproducing originals. 1.3. The Drawing Sheet 1.3.1. Sheet Sizes The sheet sizes to be used in engineering drawing are determined by the standards for format series. A distinction is made between: Format series A − e.g. for drawing sheets, post cards, filing cards, exercise−books Format series B and C− e.g. filing cards, envelopes, folders, packing cardboard The following explanations concern the format series A. The size of the initial format for drawing sheets is 841 2 mm × 1189 mm and is designated by A0. The format has an area of 1 m . The next smaller sheet size (A1) is obtained by dividing into halves of the initial format so that the basic formats A1, A2, A3, A4 and A5 are brought about (see Fig. 1.10). Fig. 1.10. Basic formats The format sizes obtained in this way can be designated by the symbol (A0 − A5) or by a 2−digit, 3−digit or 4−digit number. The short designation of the format by numbers is shown in Fig. 1.11 in the right upper 11corner. Thus the size of the formats 1.10 (spoken one − ten) is 297 mm × 2102 mm 75 (spoken seventy−five) is 2081 mm × 1051 mm 12 (spoken twelve) is 297 mm × 420 mm If one of the two numbers is 9, then it must be separated from the second number by a point. The numbers selected for the individual formats are in the following relation: The starting format is always A4 with the vertical value 297 mm = 1 unit (factor 1) and the horizontal value 210 mm = 1 unit (factor 1) 12Fig. 1.11. Short designations of formats 1 Vertical values in mm 2 Horizontal values in mm 3 Main formats in mm 4 Symbol 5 Format 3 4 135 44 1189 × 841 A 0 24 594 × 841 A 1 22 594 × 420 A 2 12 297 × 420 A 3 11 297 × 210 A 4 01 148 × 210 A 5 The first number of the short designation indicates the factor of the multiple of the vertical value (297 mm). The second number of the short designation indicates the factor of the multiple of the horizontal value (210 mm) (see Fig. 1.12). Fig. 1.12 Rule of format formation 1 Vertical value 2 Horizontal value 3 One unit 4 Two units, 5 Three units Due to the designation of the format size with the help of numbers it is possible to mark sizes which deviate from the main formats (A0 − A5). For example, this may be necessary for the representation of towers and bridges where the vertical or horizontal extension must be considerably larger than the second dimension 14involved. 1.3.2. Division and Position of the Sheet The division of a drawing sheet of size A4 (11) is shown in Fig. 1.13. Thus any drawing sheet is provided with − one filing margin (with A4 = 20 mm) − three protective margins(with A4 = each 5 mm) − one title block (185 × 25 mm) Fig. 1.13. Division of the sheet 1 Filing margin 2 Protective margin 3 Title block 4 Drawing area The remaining area is the drawing area. The possible position of the sheet of the main formats is shown in Fig. 1.14. Fig. 1.14. Position of the sheet (possibilities) Abbreviated Arrangement designations or symbols of the main formats 15Upright size Broad−size A0 44 ——— • A1 24 • • A2 22 • • A3 12 • • A4 11 • ——— The format A4 mostly used in schools is mainly of the upright size. If the broadside is exceptionally required, then the filing margin is on top. The position of the title block is not changed. Depending on the position of the sheet, the readability of the dimensional numbers must be taken into consideration (see Fig. 1.15.). Fig. 1.15. Position of the sheet (readability) 1 Title block, × 5 thick 1.3.3. Title Block and List of Parts Any engineering drawing contains a title block (see Fig. 1.16.). The title block provides space for − the designation of the represented object, − the scale selected, − the enterprise (or educational institution) where the drawing has been prepared − the day when it has been finished − the date of testing − the registration number. Fig. 1.16. Title block, simplified for drawings 16

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