In the examples of the cornflake packet shown in Figure 2.11 and the small bracket shown in Figure 2.12, six views of each component were shown. There can only ever be six views of an artefact in a full orthographic projection. The central view is invariably the front view.
Other views can be included but these will be auxiliary views. Such auxiliary views are placed remote from the orthographic views. If an artefact contains a sloping surface, the true view of the inclined surface will never be seen in orthographic projection. This can be seen in the small bracket in Figure 2.12. The bracket contains a stiffening wall which is shown on the right-hand side of the front view. This has a sloping surface as shown by the left-side view and the right-side view. However, there is no view that shows the true view of this place. This could be provided by an auxiliary view, projected from the left-side view or the right-side view that would be a view perpendicular to the inclined face. Such an inclined view would not fit comfortably within the six views of the bracket and therefore would be placed off at the side but with a note making clear that it was a view on an arrow perpendicular to the face. It is normal practice to label such arrows with some alphanumeric designation. There needs to be a title associated with the true view that relates the arrow to the view. A typical title would be 'View on arrow Z'.
Unless a part is very complex, six views of an artefact are unnecessary and over the top. The number of views will be dependent on the transmission of full and complete information of the artefact. Thus, considering the bracket in Figure 2.12, only three views would probably be needed. These would be the front view, the plan view and the left-side view. These three views would then be dimensioned and the three views plus the dimensions would be sufficient for the bracket to be made. Three such views are shown in Figure 2.14 (but the projection lines need to be rubbed out). Figure 2.16 shows two views of a flange. Since one view is a sectional view through the centre line, sufficient information can be transmitted when this part is dimensioned for it to be manufactured. In the small hand vice assembly drawing in Figure 1.11, three views are shown. The only reason that the left-hand view is shown is to give details of the screws (part number 8) which hold one of the hardened inserts to the body. An alternative method of drawing these bolts would be by adding dotted lines to the side view such that the hidden detail of the bolts was shown. In this case the balloon references would go to these dotted lines and the left-hand view would be unnecessary. However, I drew the three views because I thought it would be clearer than adding dotted lines.
The three drawings in Figure 1.11 are sufficient to assemble the various parts of the small hand vice. However, this cannot be said for the parts necessary to assemble George Stephenson's Rocket. In this case the two views would only give the barest of information about the outside shape and form. Numerous other views and indeed additional drawings would be needed to give full details on how to make and assemble the locomotive.
No hard and fast rules can be given with respect to the number of views required on any engineering drawing. The decision on the number required will be dependent on the complexity of the artefact and its internal features. In all cases the number of views will be driven by the need to give sufficient information for the part to be manufactured. One should try to avoid giving more views than is necessary because this just tends to complicate a drawing. On the other hand, if an extra view helps in the understanding of the part design, then it is a useful addition!
References and further reading
Bailey R B and Glithero J P, The Engineering History of the Rocket, a Survey Report, National Railway Museum, York, 2000.
ISO 128-24:1999, Technical Drawings - General Principles of Presentation -Part 24: Lines on Mechanical Engineering Drawings, 1999.
ISO 128-30:2001, Technical Drawings - General Principles of Presentation -Part 30: Basic Conventions for Views, 2001.
ISO 128-34:2001, Technical Drawings - General Principles of Presentation -Part 34: Views on Mechanical Engineering Drawings, 2001.
ISO 128-40:2001, Technical Drawings - General Principles of Presentation -Part 40: Basic Conventions for Cuts and Sections, 2001.
ISO 128-44:2001, Technical Drawings - General Principles of Presentation -Part 44: Sections on Mechanical Engineering Drawings, 2001.
ISO 5456-1:1996, Technical Drawings - Projection Methods - Part 1: Synopsis, 1996.
ISO 5456-2:1996, Technical Drawings - Projection Methods - Part 2: Orthographic Representations, 1996.
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