Exploded assembly drawings

Figure 7.6 shows a typical exploded assembly drawing these drawings are prepared to assist in the correct understanding of the various component positions in an assembly. Generally a pictorial type of projection is used, so that each part will be shown in three dimensions. Exploded views are invaluable when undertaking servicing and maintenance work on all forms of plant and appliances. Car manuals and do-it-yourself assembly kits use such drawings, and these are easily understood. As well as...

A drawing standard

From time immemorial, drawings have been the medium used to convey ideas and intentions. Hence the adage that 'a picture is worth a thousand words'. No need for language, the picture tells it all. In recent years there has, unfortunately, developed another opinion since CAD appeared on the scene, that there is no need for a draughtsman now as the computer does it all. The truth of the matter is that the computer is able to extend the range of work undertaken by the draughtsman and is really a...

Block diagrams

Block symbols or outlines are used to indicate the main separate elements in an installation and how they are functionally linked together. The diagram needs to be simple, so that the basics of the operation it represents, can be appreciated quickly. The block symbols refer to single hardware items or self contained units without necessarily indicating all of the exact connections. A block diagram can be presented to show a sequence of events to the reader and be used for fault diagnosis.

Size of computer

As a rough guide to selection, the larger the drawing and degree of complexity, the more important is the performance and power of the computer and its operator. If a drawing contains large areas which are crosshatched or shaded, for example, it is important to be able to redraw illustrations quickly to prevent time wasting. It is easy to obtain demonstrations of computer power and this is recommended. When selecting software products required to operate with each other, it is necessary to...

Methods of applying the tolerance frame to the toleranced feature

Figures 20.4 and 20.5 illustrate alternative methods of referring the tolerance to the surface or the plane itself. Note that in Fig. 20.5 the dimension line and frame leader line are offset. The tolerance frame as shown in Fig. 20.6 refers to the axis or median plane only of the dimensioned feature. Figure 20.7 illustrates the method of referring the tolerance to the axis or median plane. Note that the dimension line and frame leader line are drawn in line.

Theoretical circuit diagrams

True Manufacturing Wiring Diagram

Design staff will prepare theoretical circuit diagrams where all the necessary connections for the correct operation of the system are included. Different sections of industry freely use other terms, such as schematics, sequence diagrams and flow charts. In all these diagrams the component parts are arranged neatly and if possible horizontally or vertically. If several diagrams form a set, then the style of presentation should be consistent. One of the conventions with this type of diagram is...

Straight line examples

Engineering Drawing Exercises

Figure 4.17 shows three components which have each been machined from solid blocks. These examples have been prepared on a grid formed by equilateral triangles. Figure 4.17 shows three components which have each been machined from solid blocks. These examples have been prepared on a grid formed by equilateral triangles. In every case, the scale is such that each side of the triangle will be 10 mm. For each component, draw five views in first angle projection, omitting hidden detail, and assume...

Case

The profile is required to be contained within the bilateral tolerance zone. Theoretical profile with bilateral tolerance zone Theoretical profile with bilateral tolerance zone The figure below shows an example where the toleranced profile of a feature has a sharp corner. The inner tolerance zone is considered to end at the intersection of the inner boundary lines, and the outer tolerance zone is considered to extend to the outer boundary-line intersections. Sharp corners such as these could...

Method of indicating geometrical tolerances on drawings

Geometrical tolerances are indicated by stating the following details in compartments in a rectangular frame. (a) the characteristic symbol, for single or related features (i) preceded by 0 if the zone is circular or cylindrical, (ii) preceded by S0 if the zone is spherical (c) Letter or letters identifying the datum or datum systems. Third compartment datum identification letter(s) Second compartment total tolerance value in the unit used for linear dimensions Indications qualifying the...

Design layout drawings

Most original designs are planned in the drawing office where existing or known information is collected and used to prepare a provisional layout drawing before further detailed design work can proceed. This type of drawing is of a preliminary nature and subject to much modification so that the designer can collect his thoughts together. The drawing can be true to scale or possibly enlargements or reductions in scale depending on the size of the finished product or scheme, and is essentially...

The bond line

The gap between the parts, and therefore the thickness of the adhesive film, has an important bearing on the characteristics of the joint. In terms of simple strength a thick bond line will generally be a weakening feature, since the mechanical strength of the unsupported resin film is likely to be less than that of the substrates. A thick bond line can however confer advantages. The adhesive is generally more flexible than the adherents or substrates. This is particularly so in most...

Quality assurance

BS EN ISO 9000 series relates to quality systems and is produced in several sections. The principles of quality assurance embrace all activities and functions concerned with the attainment of quality. BSI Quality Management Handbook QMH 100 is essential reading. Having purchased quality CAD equipment, the products which the company propose to manufacture need to be designed and developed from conception following an agreed quality assurance working procedure practised by all employees...

The British Standards Institution

Established in 1901, The BSI was the world's first national standards body. Many similar organizations worldwide now belong to the International Organization for Standardization (ISO) and the International Electrotechnical Commission (IEC). BSI represents the views of British Industry on these bodies, working towards harmonizing world standards. BSI has published approximately 20 000 standards each year around 2000 new and revised standards are issued to encompass new materials, processes and...

Project development

The reader will appreciate that the design of, for example, a large construction project from its conception, will involve technical input from architects and engineering designers in a wide variety of associated disciplines. It is vital that all contributors to the overall scheme talk the same language and that only compatible computer software packages are in use for the separate areas of work. In addition, the management contractor must have access to the designs as work is in progress....

Heat recovery control in refrigeration systems

The principle of the refrigeration cycle is shown in Fig. 27.17. Where the refrigerant passes through the following four phases 1 evaporation (with heat absorption) 2 compression (with energy absorption) 3 condensation (with heat emission) In a refrigeration system, a second condenser can be incorporated in the cycle and the recovered heat used for 3 reheating in the case of supply air dehumidification.

Locking by adhesives

Small components found in, for example, instruments and switches may be locked by the application of Shellac, Araldite, Loctite, or similar materials. Shellac and Loctite are usually applied to the threads of nuts, bolts, screws and studs and the components are assembled while still wet. The parts should be free from grease to achieve maximum strength. Araldite is applied to the outside of the nut face and the protruding screw thread, after tightening. Araldite is an adhesive which hardens,...

Computer aided draughting and design

CAD is much more than drawing lines by electronic means. Similarly by the purchase of a CAD system, a design does not emerge at the push of a button. 'Buy a computer and you don't need a draughtsman' is also very different from reality. The engineering designer is very much responsible for decisions taken at all technical stages between conception and production. The computer is an aid and performs as it is directed with rapidity and accuracy. The following notes are included to indicate areas...

Building management

Figure 27.8 and 27.9 show possible schemes for partial and full air conditioning. In addition to the controls indicated there will be all the associated ductwork, filters, water, steam and electrical services. An electrical control panel is usually necessary for the wiring of interconnected equipment, instrumentation, and to isolate plant for servicing. Although operations are generally fully automatic, emergency hand control facilities are often specified. In an industrial situation where many...

Pneumatics and electronics

Systems of low complexity and those in use in hazardous areas, not compatible with electronics, will probably be designed as pure pneumatic systems. A purely pneumatic system can be viewed as three main sections 1 Generation and preparation of the compressed air source. 2 Power actuation of pneumatic cylinders through directional control valves. 3 Pneumatic signal processing or logic control. Electronics can influence all of these sections, for example (a) By electronic management control of...

Sections through thin material

Many products are manufactured from very thin materials which would be virtually impossible to cross hatch in a sectional view and in these cases it is usual to make them entirely black. Where however two or more thin sections are adjacent to each other, a gap is left so that the profile of the separate components is clearly defined. A compound stanchion used in structural steelwork and drawn to reduced scale is shown in Fig. 8.12. The same situation applies with sections through sheet-metal...

CAD organization and applications

Computing developments have made a rapid and immense impact on industry and commerce and as the degree of complexity has also increased, then training facilities have expanded accordingly. As a source of information and communication, the Technical Press and the Internet play a very important part. Journals from professional institutions offer impartial news, advice and guidance, opinions, and new product details. Manufacturers and the larger suppliers of CAD equipment have set up centres...

Indication of datum targets

(a) a point it is indicated by a cross X (b) a line it is indicated by two crosses, connected by a thin (c) an area it is indicated by a hatched area surrounded by a thin double dashed chain All symbols apear on the drawing view which most clearly shows the relevant surface.

The application of thread conventions

Engineering Drawing Exercises

Figure 15.21(a) shows an elevation of a stud in a tapped hole. When a mating thread is screwed into a tapped hole, the section lines do not cover the assembled threads, also, the threads on the stud terminate at the start of the hole to signify that the stud is screwed to maximum depth. Adjacent parts in the sectional view are cross hatched in opposite directions. It is not normal practice to section nuts, bolts and washers. Exercise Draw a similar assembly using a M24 stud. The stud is screwed...

Limits and fits

Interference Fit

To ensure that an assembly will function correctly, its component parts must fit together in a predictable manner. Now, in practice, no component can be manufactured to an exact size, and one of the problems facing the designer is to decide the upper and lower limits of size which are acceptable for each of the dimensions used to define shape and form and which will ensure satisfactory operation in service. For example, a dimension of 10 0.02 means that a part will be acceptable if manufactured...

Combined detail and assembly drawings

Simple Assembly Drawings

It is sometimes convenient to illustrate details with their assembly drawing on the same sheet. This practice is particularly suited to small 'one-off' or limited-production-run assemblies. It not only reduces the actual number of drawings, but also the drawing-office time spent in scheduling and printing. Figure 7.5 shows a simple application of an assembly of this type. 7.3 Assembly drawing of gear and bearing Fig. 7.5 Combined detail and assembly drawing of hub-puller

Sheet metalwork application

Engineering Drawing Machining Symbols

The design of components to be manufactured from folded sheet metal is a field in which CAD systems can offer great assistance. In the case of the bracket shown in Fig. 3.3 it would first be necessary to establish the overall dimensions of the part. The second step would be to imagine that the bracket is folded back gradually as indicated in Fig. 3.4 into the flat sheet form. This shape would then be stamped from metal strip in a power press. The dimensions of the flat pattern have to make...

Drawing office management and organization

Basic Drawing Office Layout Chart

Every article used in our day-to-day lives will probably have been produced as a result of solutions to a sequence of operations and considerations, namely The initial stage will commence when an original marketable idea is seen to have a possible course of development. The concept will probably be viewed from an artistic and a technological perspective. The appearance and visual aspects of a product are very important in creating an acceptable good first impression. The technologist faces the...

Designing for adhesives

For the best possible performance, joints should be specifically designed for adhesive bonding. Follow this principle and much better joints will be achieved than if bonding is adopted as a substitute for welding in a joint designed for that purpose. Bond stresses, materials, type of adhesive, surface preparations, method of application and production requirements can then all be considered in relation to each other at the outset. The designer should consider especially the effect of shear,...

Tolerance zones

The width of the tolerance zone is in the direction of the leader line arrow joining the symbol frame to the toleranced feature unless the tolerance zone is preceded by the symbol 0. An example is given in Fig. 20.15a. If two tolerances are given, then they are considered to be perpendicular to each other, unless otherwise stated. Figure 20.15b shows an example. Figure 20.15c gives an example where a single tolerance zone is applied to several separate features. In the tolerance frame the...

Threadcutting screws

Machine Screw Thread Engagement

Barber and Colman Ltd are the manufacturers of 'Shakeproof' thread-cutting screws and washers. 'Shakeproof' thread-cutting screws made from carbon steel are subjected to a special heat-treatment which provides a highly carburized surface with a toughened resilient core. The additional strength provided enables higher tightening torques to be used, and will often permit the use of a smaller-size thread-cutting screw than would normally be specified for a machine screw. Thread-cutting screws...

End Face Run-out

Cumulative Radial Runout

The component is required to be rotated about datum axis C, with datum face B set to ensure no axial movement. The circular radial runout on the cylindrical portion must not exceed 0.05 at any point measured perpendicular to the datum axis. The circular runout on the tapered portion must not exceed 0.07 at any point measured normal to its surface. The circular runout on the curved portion must not exceed 0.04 at any point measured normal to its surface. The axial runout of the end face must not...

Interchangeable systems

Fig. 19.9 Elements of interchangeable systems Fig. 19.9 Elements of interchangeable systems Nominal size is the size by which a component is referred to as a matter of convenience, i.e. 25 mm, 50 Basic size is the size in relation to which all limits of size are fixed, and will be the same for both the male Limits of size These are the maximum and minimum permissible sizes acceptable for a specific dimension. Tolerance This is the total permissible variation in the size of a dimension, and is...

Chain lines

Chain Line Dimensioning

Particular care should be taken with chain lines to ensure that they are neatly applied and attention is drawn to the following points a All chain lines should start and finish with a long dash. b When centre points are defined, then the chain lines should cross one another at solid portions of the line. c Centre lines should extend for a short distance beyond the feature unless they are required for dimensioning or other purpose. Fig. 5.3 Example showing imaginary lines of intersection Fig....

Heating ventilation and air conditioning systems

Engineering Drawing Block Unit

Control systems are devised to suit each individual application. Generally, each part of the system will contain air of different types. With reference to Fig. 27.6 the room air RA is extracted by a fan, a proportion of the air is exhausted to atmosphere and the remainder Note. This diagram forms an introduction to the basic system concept highlighting the major functional areas of the overall system. It is intended for users who require a basic appreciation of the system. Note. This diagram...

Fig Cam operated clamp

Engineering Drawing Assembly Example

This example shows a typical assembly and includes a parts list. The balloons containing the part numbers are equally spaced whenever possible. The leader lines to the components terminate in a dot. The leader line is also directed towards the centre of the balloon and touches the circumference. It is considered good policy to position the parts list and commence writing in such a way that parts can be added on to the end of the list in the event of future modifications. The list can be drawn...

Examples involving radii and holes

For each example, project five views in first angle projection, taking the view in the direction of the arrow A as the front view. Hidden detail is required in the solutions to these problems, and note that in some cases the position of some of the holes will be found to coincide with centre lines. Where this occurs the dotted line should take priority. Take each side of the grid triangle to be 10 mm in length. If only three views of each component were required, which ones would you choose The...

Interpretations of limits of size in relation to form

There are two ways of interpreting the limits of size of an individual feature, which are known by 1 The Principle of Independency, where the limits of size apply to local two point measurements of a feature regardless of form. 2 The Envelope Requirement, also known as The Taylor Principle, where the limits of size of an individual feature are intended to have a mutual dependency of size and form. Issue 1. February 1970 confirmed August 1985 Diagram to scale for 25 mm diameter f BRITISH...

Wiring diagrams for motor vehicles

The following diagrams are reproduced by kind permission of the Ford Motor Company Ltd and show part of the wiring circuit for the Transit van. Service manuals need to be presented so that the technician can easily check each function for satisfactory operation. The manual is therefore written with each circuit shown completely and independently in one chapter or 'cell'. Other components which are connected to the circuit may not be shown unless they influence the circuit operation. For the...

Typical AutoCAD drawings

Autocad Drawing Exercise

The following examples are meant to convey to the reader the extensive range of draughting facilities available from software associated with basic programs. Obviously there is a certain amount of overlap in the scope of programs and often alternative ways of performing similar operations. Figures 3.6 and 3.7 show pictorial drawings of an engine development. A pictorial view can easily be generated after drawing orthographic views, which give the dimensions in three planes at right angles to...

Screw threads and conventional representations

Drawing Metric Coarse Threads

The most common application of the helix is in a screw thread which follows the path of the helix. Screw threads may be either left or right hand and these are shown pictorially in Fig. 15.1. Notice the slope of the thread and the position of the index finger on each hand. The left hand thread is used for special applications and the right hand thread is the one normally used on nuts and bolts. The thread illustrated has a vee-section. The following terms are associated with screw threads The...

Simplified drawings

Engineering Drawing Slots

Simplified draughting conventions have been devised to reduce the time spent drawing and detailing symmetrical components and repeated parts. Figure 7.7 shows a gasket which is symmetrical about the horizontal centre line. A detail drawing indicating the line of symmetry and half of the gasket is shown in Fig. 7.8, and this is sufficiently clear for the part to be manufactured. If both halves are similar except for a small detail, then the half which contains the exception is shown with an...

Projected toleranced zone

Projected Tolerance Zone

Figure 20.16 shows a part section through a flange where it is required to limit the variation in perpendicularity of each hole axis. The method used is to apply a tolerance to a projected zone. The enlargement shows a possible position for the axis through one hole. Each hole axis must lie somewhere within a projected cylinder of 0 0.02 and 30 deep. Note. Projected tolerance zones are indicated by the symbol . Figure 20.16 shows a part section through a flange where it is required to limit the...

Preface

This latest edition of A Manual of Engineering Drawing has been revised to include changes resulting from the introduction of BS 8888. British Standard 308 was introduced in 1927 and acknowledged by Draughtsmen as THE reference Standard for Engineering Drawing. The British Standards Institution has constantly kept this Standard under review and taken account of technical developments and advances. Since 1927, major revisions were introduced in 1943, 1953, 1964 and 1972 when the contents of BS...

Successive sections

Successive Auxiliary View

Figure 8.14 shows the front and end elevations of a special purpose mounting plate where sectional plans are given at different levels to illustrate the shapes of the various cutouts and details. Now it will be noted that the presentation of this problem takes considerable vertical space since all of the plan views are in correct projection. The current British Standard permits successive sections to be drawn as shown in Fig. 8.14. Figure 8.14 shows the front and end elevations of a special...

Application of bearings

A rotating machine element, e.g. the shaft, generally requires two bearings to support and locate it radially and axially relative to the stationary part of the machine, e.g. the housing. Normally, only one of the bearings the locating bearing is used to fix the position of the shaft axially, whilst the other bearing the non-locating bearing is free to move axially. Axial location of the shaft is necessary in both directions and the locating bearing must be axially secured on the shaft and in...

Approximate construction for nuts and bolts Figs and

1 Draw a circle in the plan position, 2D in diameter, where D is equal to the thread size. In this example let us assume that the thread size is M20. 2 Draw a hexagon inside the 40 mm diameter circle and inside the hexagon draw another circle tangential to the hexagon on the six sides. This circle is the projection of the chamfer which can be seen on the front elevation. the nut thickness is 0.8D. Project the four corners of the hexagon to the front elevation. Project three corners of the...

Lubrication

Grease lubrication is generally used where ball and roller bearings operate at normal speeds, temperature and loading conditions. Grease has certain advantages by comparison with oil it is more easily retained in the bearing housing and assists in sealing against the entry of dirt and moisture. In general the free space in the bearing and housing should only be partly filled with grease 30 to 50 . Overfilling causes rapid temperature rise particularly if speeds are high. Manufacturers supply...

Drawing modifications

After work has been undertaken on a drawing for a reasonable amount of time, then that drawing will possess some financial value. The draughtsman responsible for the drawings must be concerned with the reproducible quality of his work as prints or photographic copies are always taken from the originals. Revisions and modifications are regularly made to update a product, due for example, to changes in materials, individual components, manufacturing techniques, operating experience and other...

Air engine

Engineering Drawing Detail Components

The component parts of an oscillating air engine are detailed in Fig. 18.5. Draw in first angle projection and, at twice full size, the following views a A front view taken as a section through the engine cylinder and flywheel. b A plan view in projection with the front view and drawn below the front view. c An end view on the right hand side and in projection with the front view. Hidden detail is not required in any view. Add a parts list to your drawing and reference balloons to identify each...

Half sections

Revolved Section Spanner

Symmetrical parts may be drawn half in section and half in outside view. This type of drawing avoids the necessity of introducing dotted lines for the holes and the recess. Dimensioning to dotted lines is not a recommended practice. Fig. 8.8 A special spanner is illustrated in Fig. 8.8. A revolved section is shown on the handle to indicate the shape of the cross section at that point. This is a convenient convention to use on single view drawings because the shape could not be confirmed without...

Scale used in geometric construction

Geometric Construction Drawing

Figure 7.16 shows the method of dividing a given line AB, 89 mm long, into a number of parts say 7 . Draw line AC, and measure 7 equal divisions. Draw line B7, and with the tee-square and set-square draw lines parallel to line B7 through points 1 to 6, to give the required divisions on AB. Fig. 7.18 Diagonal scale where 40 mm represents 1000 mm Figure 7.16 shows the method of dividing a given line AB, 89 mm long, into a number of parts say 7 . Draw line AC, and measure 7 equal divisions. Draw...

Sections and sectional views

Section Views Engineering Drawings

A section is used to show the detail of a component, or an assembly, on a particular plane which is known as the cutting plane. A simple bracket is shown in Fig. 8.1 and it is required to draw three sectional views. Assume that you had a bracket and cut it with a hacksaw along the line marked B-B. If you looked in the direction of the arrows then the end view B-B in the solution Fig. 8.2 , would face the viewer and the surface indicated by the cross hatching would be the actual metal which the...

Engineering applications

Horizontal Structural Irregularities

The following examples show varied uses of engineering adhesives in industry. Locking screw threads The liquid is applied to the cleaned thread of a bolt or stud. When the nut is tightened the liquid fills the gaps between mating threads and hardens to form a tough plastic joint which is shock, vibration, corrosion and leak proof. The joint will remain in place until it needs to be undone again using normal hand tools. Threadsealing pipe fittings The sealant is applied to the clean thread and...

Ball and roller bearings

Pressed Powder Bearings

Each type of bearing has characteristic features which make it particularly suitable for certain applications. However, it is not possible to lay down hard and fast rules for the selection of bearing types since several factors must be considered and assessed relative to each other. The following recommendations will, for a given application, serve to indicate those details of greatest importance in deciding the type of bearing to be used. In many instances at least one of the main dimensions...

Helical extension springs

Helical Coil Drawing

A helical extension spring is a spring which offers resistance to extension. Almost invariably they are made from circular-section wire, and a typical selection is illustrated in Fig. 25.12. The conventional representations of tension springs are shown in Fig. 25.13 and a schematic drawing for detailing is shown in Fig. 25.14. Coils of extension springs differ from those of compression springs in so far as they are wound so close together that a force is required to pull them Fig. 25.13...

Circular runout

Circular run-out is a unique geometrical tolerance. It can be a composite form control relating two or more characteristics, and it requires a practical test where the part is rotated through 360 about its own axis. The results of this test may include errors of other characteristics such as circularity, concentricity, perpendicularity, or flatness, but the test cannot discriminate between them. It should therefore not be called for where the design function of the part necessitates that the...

Taper pins and parallel pins

Taper Engineering Drawings

Taper pins, with a taper of 1 in 50, and parallel pins are used on both solid and tubular sections to secure, for example, levers to torque shafts and control rods to fork ends. Some taper pins are bifurcated, or split, and the legs can be opened out for locking. Plain taper pins and parallel pins may also be locked by peening. To prevent slackness, these pins are assembled in accurate reamed holes. Undue force should not be used during the peening process or the security of the fittings may be...

Involute gear teeth proportions and relationships

Number of teeth, T Circular pitch n x module Addendum module Clearance 0.25 x module Dedendum addendum clearance Involute gears having the same pressure angle and module will mesh together. The British Standard recommendation for pressure angle is 20 . The conventional representation of gears shown in Fig. 24.16 is limited to drawing the pitch circles and outside diameters in each case. In the sectional end elevation, a section through a tooth space is taken as indicated. This convention is...

Assembly drawings

Technical Drawing Bolt

Machines and mechanisms consist of numerous parts, and a drawing which shows the complete product with all its components in their correct physical relationship is known as an assembly drawing. A drawing which gives a small part of the whole assembly is known as a sub-assembly drawing. A sub-assembly may in fact be a complete unit in itself for example, a drawing of a clutch could be considered as a sub-assembly of a drawing showing a complete automobile engine. The amount of information given...

Maximum material condition applied to position

A typical drawing instruction is given in Fig. 22.8, and the following illustrations show the various extreme dimensions which can possibly arise. Minimum distance between hole centres and the maximum material condition of holes. Maximum distance between hole centres and maximum material condition of holes To give the same assembly condition as in A, the minimum distance between hole centres is reduced when the holes are finished away from the maximum material condition. To give the same...

First angle projection examples with plotted curves

Third Angle Projection

In orthographic projection, all widths in the end view are equal in size to depths in the plan view, and of course the opposite is true that some dimensions required to complete end views may be obtained from given plan views. Figure 4.21 shows part of a solid circular bar which has been cut at an angle of 30 with the horizontal axis. Point A is at any position along the sloping face. If a horizontal line is drawn through A across to the end view then the width of the chord is dimension X. This...

The application of tolerances to a restricted length of a feature

Figure 20.12 shows the method of applying a tolerance to only a particular part of a feature. Figure 20.12 shows the method of applying a tolerance to only a particular part of a feature. The tolerance frame in Fig. 20.13 shows the method of applying another tolerance, similar in type but smaller in magnitude, on a shorter length. In this case, the whole flat surface must lie between parallel planes 0.2 apart, but over any length of 180 mm, in any direction, the surface must be within 0.05....

Unified threads

Standard For Engineering Drawing

The Unified system of screw threads was introduced by the United Kingdom, Canada and the United States to provide a common standard thread for use by the three countries. The International Standards Organisation ISO recommends the system as an international system of screw threads in inch units, in parallel with a similar system in metric units. Both of these systems use a similar form of thread profile which is illustrated basically in Fig. 15.4. Fig. 15.4 Unified screw thread H 0.86603P, Rc...

Torsion springs

Engineering Drawing Spring

Various forms of single and double torsion springs are illustrated in Fig. 25.8. Figure 25.9 gives a schematic diagram for a torsion spring. This type of drawing, adequately dimensioned, can be used for detailing. Figure 25.9 gives a schematic diagram for a torsion spring. This type of drawing, adequately dimensioned, can be used for detailing. ends of the wire in the spring may be straight, curved, or kinked.

Mech Soft

Gearbox Engineering Drawing

The MechSoft program contains many wizards, used to assist in the design of a large variety of mechanical solutions, which conform to National and Company Standards. The detailed component drawings are of the parametric type all are mechanically correct and used to create automatically, new components. All of these parts are compatible with the Autodesk Inventor Series. A typical small assembly is shown in Fig. 3.21. A gearbox is to be manufactured in a range of sizes using standardized...

Maximum material condition applied to coaxiality

Datum Axis

In the previous examples, the geometrical tolerance has been related to a feature at its maximum material condition, and, provided the design function permits, the tolerance has increased when the feature has been finished away from the maximum material condition. Now the geometrical tolerance can also be specified in relation to a datum feature, and Fig. 22.13 shows a typical application and drawing instruction of a shoulder on a shaft. The shoulder is required to be coaxial with the shaft,...

Keys and keyways

A key, Fig. 17.1, is usually made from steel and is inserted between the joint of two parts to prevent relative movement it is also inserted between a shaft and a hub in an axial direction, to prevent relative rotation. A keyway, Figs. 17.2, 17.3 and 17.4, is a recess in a shaft or hub to receive a key, and these recesses are commonly cut on key-seating machines or by broaching, milling, planing, shaping and slotting. The proportions of cross-sections of keys vary with the shaft size, and...

Dimensioning principles

Dimensioning Rules

A drawing should provide a complete specification of the component to ensure that the design intent can be met at all stages of manufacture. Dimensions specifying features of size, position, location, geometric control and surface texture must be defined and appear on the drawing once only. It should not be necessary for the craftsman either to scale the drawing or to deduce dimensions by the subtraction or addition of other dimensions. Double dimensioning is also not acceptable. Theoretically...

Development of patterns from sheet materials

Many articles such as cans, pipes, elbows, boxes, ducting, hoppers, etc. are manufactured from thin sheet materials. Generally a template is produced from an orthographic drawing when small quantities are required larger quantities may justify the use of press tools , and the template will include allowances for bending and seams, bearing in mind the thickness of material used. Exposed edges which may be dangerous can be wired or folded, and these processes also give added strength, e.g....

Product development and computer aided design

Work undertaken by a drawing office will vary considerably with different branches of industry. Generally, work of a 'design and make' nature will follow a plan which sets out stages in development from the time a potential client makes an enquiry until the completed product is delivered. The function of the product will dictate many of the associated activities. A vehicle manufacturer will not design and make all of the parts used but subcontract components from specialists. The engine...

Cam followers

Various types of cam followers are shown in Fig. 24.1. Knife-edge followers are restricted to use with slow-moving mechanisms, due to their rapid rates of wear. Improved stability can be obtained from the roller follower, and increased surface area in contact with the cam can be obtained from the flat and mushroom types of follower. The roller follower is the most expensive type, but is ideally suited to high speeds and applications where heat and wear are factors. Fig. 24.1 Plate cams a Plate...

Machine drawing

Bs8888 Drawing Fixings

The draughtsman must be able to appreciate the significance of every line on a machine drawing. He must also understand the basic terminology and vocabulary used in conjunction with machine drawings. Machine drawings of components can involve any of the geometrical principles and constructions described in this book and in addition the accepted drawing standards covered by BS 8888. Figure 7.15 illustrates many features found on machine drawings and the notes which follow give additional...

Reading engineering drawings

Reading Engineering Drawings

The following notes and illustrations are intended to assist in reading and understanding simple drawings. In all orthographic drawings, it is necessary to project at least two views of a three dimensional object - or one view and an adequate description in some simple cases, a typical example being the drawing of a ball for a bearing. A drawing of a circle on its own could be interpreted as the end elevation of a cylinder or a sphere. A drawing of a rectangle could be understood as part of a...

Chain dimensioning and auxiliary dimensioning

Draw Charcoal Colored Paper Landscape

Chains of dimensions should only be used where the possible accumulation of tolerances does not endanger the function of the part. A plan view of a twist drill stand is given in Fig. 14.5 to illustrate chain dimensioning. Now each of the dimensions in the chain would be subject to a manufacturing tolerance since it is not possible to mark out and drill each of the centre distances exactly. As a test of drawing accuracy, start at the left hand side and mark out the dimensions shown in turn....

Geometrical constructions and tangency

Across The Flats Hexagon

Students will often experience difficulty in handling problems involving two and three dimensional geometrical constructions. The examples in Chapters 9 to 13 are included in order to provide a background in solving engineering problems connected with lines, planes and space. The separate chapters are grouped around applications having similar principles. Copying a selection of these examples on the drawing board or on CAD equipment will certainly enable the reader to gain confidence. It will...

Requirements

Requirements Engineering Cartoon

Figure 14.43 shows mandatory positions of associated surface texture requirements. Note that in accordance with BS EN ISO 1302 2002 the position 'X' is no longer used. Only positions a, b, c, d and e should be used. Position 'a' indicates one single surface texture requirement. Positions 'a' and 'b' indicate two or more surface texture requirements. Position 'c' indicates manufacturing method, treatment, coating or other process. Position 'd' indicates surface lay. Position 'e' shows machining...

Socket head screws manufactured to Bs En Iso and BS

It is often required to draw these screws and although the head type and the length are generally quoted in parts lists it is necessary to know the proportions of the head. Dimensions follow for each of the most commonly used screws. Before specifying screws it is advisable to consult a manufacturers list for availability. In the interest of standardization and economy, designers are urged to use stock lengths wherever possible and standard lengths of screws include the following 3, 4, 5, 6, 8,...

Disc springs

Disc Spring Stack

For bolted connections a very simple form of compression spring utilizes a hollow washer manufactured from spring steel, although other materials can be specified. Table 25.1 shows a selection of Belleville washers manufactured to DIN 6796 from spring steel to DIN 17222. If the disc has its top and bottom surfaces ground to approximately 95 of the appropriate thickness in the table above then bearing surfaces will be formed. These surfaces improve guidance where several discs are used together....

Mockups and prototypes

Mockups and prototypes show how products and mechanisms look and perform but building them is a time-consuming process. A 3D model is life-like, popular and can be of considerable assistance for publicity purposes especially where the client has limited technical experience. Recent developments are easy to use and an economical method of demonstrating engineering design concepts. Drawings can be communicated by email and have the advantage that they can be viewed by anyone who has a Windows PC....

Fig Air engine assembly illustrated below

Orthographic Assembly Drawing

The engine operates through compressed air entering the cylinder via one of the connecting pipes shown as item 15. The other pipe serves to exhaust the cylinder after the power stroke. The cylinder oscillates in an arc and a hole through the cylinder wall lines up with the inlet and exhaust pipes at each 180 of rotation of the flywheel. The spindles Parts 4 and 18 , grub screw Part 5 and the pin Part 11 would not normally be sectioned. A part section is illustrated at the bottom of the...

Isometric projection

Engineering Drawing Isometric Projection

Figure 6.1 shows three views of a cube in orthographic projection the phantom line indicates the original position of the cube, and the full line indicates the position after rotation about the diagonal AB. The cube has been rotated so that the angle of 45 between side AC1 and diagonal AB now appears to be 30 in the front elevation, C1 having been rotated to position C. It can clearly be seen in the end view that to obtain this result the angle of rotation is greater than 30 . Also, note that,...

Locking plates

Locking Plates Engineering

Locking plates are manufactured usually from mild steel and fit over hexagonal nuts after these have been tightened on assembly. The locking plate is then secured on the component by a separate screw which may itself be fitted with a shakeproof or spring type of washer. Locking plates may be used repeatedly, provided they remain a good fit, around the hexagon of the nut or the bolthead. Locking plates may be cranked, as in Fig. 16.28 or flat. Figure 16.29 shows a selection of locking terminals...

Dimensioning keyways parallel keys

Keyway Slot

The method of dimensioning a parallel shaft is shown in Fig. 17.15, and a parallel hub in Fig. 17.16. Note that in each case it is essential to show the dimension to the bottom of the keyway measured across the diameter of the shaft and the bore of the hub. This practice cannot be used where either the shaft or hub is tapered, and Fig. 17.17 shows the method of dimensioning a keyway for a square or rectangular parallel key in a tapered shaft, where the keyway depth is shown from the outside...

Oblique projection

Plan Oblique Projection

Figure 6.8 shows part of a plain bearing in orthographic Fig. 6.3 Construction principles for points in space, with complete solution Figure 6.8 shows part of a plain bearing in orthographic Fig. 6.3 Construction principles for points in space, with complete solution Fig. 6.4 Views b , c and d are isometric projections of the section in view a Fig. 6.4 Views b , c and d are isometric projections of the section in view a Fig. 6.6 Isometric constructions for corner radii Fig. 6.6 Isometric...

Split cotter pins

Ferrous and non ferrous split cotter pins are covered by BS 1574. The designating size of a split cotter pin is the size of the hole for which it is intended to fit. When reference is made to a split cotter pin in a parts list, this nominal dimension is followed by the length required. The closed legs of the shank of the pin form a circular cross section. The legs should be straight and parallel throughout their nominal length. Figure 16.32 shows alternative pins in detail. Alternative shape of...

Plain bearings

Drawing Plain Bearing

Plain bearings may be classified as follows Plain bearings a Solid inserts b Lined inserts c Wrapped ii Medium walled insert liners iii Thin walled insert liners. The bearing metal should have a low coefficient of sliding friction, be able to conduct heat generated away from the bearing surfaces, resist wear in use and be tough enough to withstand shock loading in service. In the event of breakdown due to lack of lubrication, it may be desirable when overheating occurs for the bearing material...

Cams and gears

A cam is generally a disc or a cylinder mounted on a rotating shaft, and it gives a special motion to a follower, by direct contact. The cam profile is determined by the required follower motion and the design of the type of follower. The motions of cams can be considered to some extent as alternatives to motions obtained from linkages, but they are generally easier to design, and the resulting actions can be accurately predicted. If, for example, a follower is required to remain stationary,...

Projection exercises

It is clear to us after teaching draughting and CAD for many years that visualizing a proposed new product in three dimensions, which is how you naturally view a finished article, is difficult when it is necessary to read more than one complex two dimensional drawing simultaneously. The draughtsman also ultimately needs to produce technically correct drawings, often from vague initial ideas. The very action of making proposal drawings stimulates many questions and their answers allow...

Worked examples in machine drawing

Machine Drawing

Examination questions generally relate to single parts or assemblies of detailed components, and test the students' ability to draw sectional and outside views. British Standards refer to 'views' but other terms have been traditionally used in technical drawing. The front or side view of a house is quite likely to be known as an elevation and a 'birds eye view' as a plan. These expressions are freely used. The examples which follow are of examination standard and a student draughtsman would be...

Bushed bearing bracket

Hand Drill Technical Drawings

Front and end views of a bushed bearing bracket are shown in Fig. 18.1. Copy the given front view and project from it a sectional end view and a sectional plan view taken from cutting planes A-A and B-B. Figure 18.2 shows details of a table for a drilling machine. Draw half full size the following views a A front view taken as a section along the cutting plane A-A. b The given plan view with hidden detail. c An end view projected to the left of the front view with hidden detail included. 5...

General engineering graphical symbols

Construction Drawing Series lists the following Part 1 - Buildings and parts of buildings Part 2 - Room names and numbers Part 3 - Room identifiers BS EN ISO 6284 Indication of Limit Deviations BS EN ISO 8560 Representations of modular sizes, lines and grids BS EN ISO 9431 Spaces for drawing for text and title block on drawing BS EN ISO 3766 Simplified representation of concrete reinforcement BS EN ISO 7518 Simplified representation of demolition and rebuilding BS EN ISO 11091 Landscape drawing...

Profile tolerance of a surface

Profile tolerance of a surface is used to control the ideal form of a surface, which is defined by theoretically exact boxed dimensions and must be accompanied by a relative tolerance zone. The profile-tolerance zone, unless otherwise stated, is taken to be bilateral and equally disposed about its true-form surface. The tolerance value is equal to the diameter of spheres whose centre lines lie on the true form of the surface. The zone is formed by surfaces which touch the circumferences of the...

The involute

Engineering Drawing Involute

The involute is defined as the path of a point on a straight line which rolls without slip along the circumference of a cylinder. The involute curve will be required in a later chapter for the construction of gear teeth. 1 Draw the given base circle and divide it into, say, 12 equal divisions as shown in Fig. 10.8. Generally only the first part of the involute is required, so the given diagram shows a method using half of the length of the circumference. 2 Draw tangents at points 1, 2, 3, 4, 5...

Typical product requirement

Dimensioning Equispaced Holes

In the example shown in Figs 23.2 and 23.3, the hole axis must lie within the cylindrical tolerance zone fixed Some advantages of using this method are 1 interpretation is easier, since true boxed dimensions fix the exact positions of details 2 there are no cumulative tolerances 3 it permits the use of functional gauges to match the mating part 4 it can ensure interchangeability without resorting to small position tolerances, required by the coordinate tolerancing system 5 the tolerancing of...

Typical example using Professor Unwins approximate construction

Addendum Circle Radius

Module, 12 mm Number of teeth, 25. Pitch-circle diameter module x no. of teeth 12 x 25 300 mm Addendum module 12 mm Clearance 0.25 x module 0.25 x 12 3 mm Dedendum addendum clearance 12 3 15 mm Circular pitch n x module n x 12 37.68 mm Tooth thickness 1 x circular pitch 18.84 mm a Draw the pitch circle and the common tangent. b Mark out the pressure angle and the normal to the line of action. c Draw the base circle. Note that the length of the normal is the base-circle...

Dimensioning of welds

Throat Thickness Leg Length Fillet Weld

The dimensions of a weld may be added to a drawing in the following manner. Dimensions relating to the cross section of the weld are symbolized by b and are given on the left-hand side of the symbol. The cross-sectional dimension to be indicated for a fillet weld is the leg length. If the design throat thickness is to be indicated then the leg-length dimension is prefixed with the letter b and the design throat thickness with the letter a. Longitudinal dimensions are symbolized by l and are...

International Organization for Standardization ISO

ISO is made up of national standards institutes from countries large and small, industrialized and developing, in all regions of the world. ISO develops voluntary technical standards, which add value to all types of business operations. They contribute to making the development, manufacturing and supply of products and services more efficient, safer and cleaner. They make trade between countries easier and fairer. ISO standards also serve to safeguard consumers, and users in general, of...

Parametric design

Cad Drawing M20 Spindle

It is a common drawing office practice, where a range of parts are similar, to produce a single drawing with a table of dimensions for the features of each separate component. The user will then need to sort out the appropriate sizes of each detail relating to the part required. The drawing itself being representative of a number of similar parts cannot be drawn true to scale for them all. A study of Fig. 3.1 will show a special screw, which has a family of parts. It is defined on a single...

The psychrometric chart

Psychrometric Chart

In air conditioning technology, it is necessary to define thermodynamic processes and the properties of moist air. This may be achieved by a good knowledge of physics, with theoretical calculations using complicated formulae and tables. The procedure can be time consuming. By presenting the interrelated factors on a psychrometric chart, an immediate decision can be made regarding the feasibility of controlling an air conditioning system and the means required to carry this out. For a given air...

The application of welding symbols to working drawings

The following notes are meant as a guide to the method of applying the more commonly used welding symbols relating to the simpler types of welded joints on engineering drawings. Where complex joints involve multiple welds it is often easier to detail such constructions on separate drawing sheets. Each type of weld is characterized by a symbol given in Table 26.1 Note that the symbol is representative of the shape of the weld, or the edge preparation, but does not indicate any particular welding...