ASME Y14.3:2003 pdf free download – MULTIVIEW AND SECTIONAL VIEW DRAWINGS
1.5 Orthographic View
An orthographic view is the figure outlined upon theprojection plane by means of the system of orthographicprojection. Such a view shows the true shape of a surfaceparallel to the projection plane (area ABCD with hole
in Fig.1). When an area is not parallel to the plane, theview of the area will be foreshortened (area BCEF inFig.1).
1.6 Projection Systems
The two internationally recognized systems of projec-tion are third angle projection and first angle projection.Unless otherwise stated,this Standard features thirdangle projection.
1.6.1 Third Angle Projection. Third angle projectionis the formation of an image or view upon a plane ofprojection placed between the object and the observer.Third angle projection is the accepted method used inthe United States. See Fig. 2.
1.6.2 First Angle Projection. First angle projectionplaces the object between the observer and the planeof projection. This method of projection used in somecountries is herein described, in consideration of theneed to interchange engineering drawings in an interna-tional market. See Fig.3.
1.6.3 View Relationships. Note that the orthographicviews of the object have the same configuration in boththe first and third angle projections, but the placementof the views with respect to one another is different. Thevisibility of lines is always taken from the observer’spoint of view.See Figs. 4 and 5.
1.6.3.1 Alternative Practice,Reference ArrowMethod. When it is desired to achieve compliance withISO practices, reference arrows and view letters may beused for all views. These practices are in agreement withISO 128-30. View identification for the reference arrowmethod does not include the word VIEW,and the identi-fying letter is placed above the view. Reference arrowsmay be shown in the CAD model, in an axonometricview, or on one of the principal orthographic views.When the reference arrow method is used, it shall beused for all views within the drawing. See Fig. 6. Refer-ence arrow proportions are defined in Fig.7.
1.7.2 Removed Views. Under certain conditions itmay be impracticable to place a view in its normalaligned position. In this instance, viewing indicators areused to indicate from where the view was taken, andthe view is removed to another location on the field ofthe drawing. See Fig. 9.Removed views are preferablyshown on the same sheet from which the view has beentaken. The removed view is identified using the viewletters.The removed view may be drawn at the samescale as the view from which it is taken, or it may bedrawn at a noted scale. It is also permissible to use acombination of numbers and letters for removed viewidentification.
1.7.5 Rotated Views. Due to the large size of depicteditems and limitations on the height or width of thedrawing format, a view may be rotated within theboundaries of a drawing sheet rather than maintain theorientation and split the view over two or more sheets.The angle and direction of rotation shall be placedbeneath the view title. See Fig.11.
1.7.6 Rotated Views Alternative Practice. When usingthe reference arrow method, the direction of rotation isindicated by an arc and arrow. The angle of rotation isnoted adjacent to the arc. See Fig. 12.Arc and arrowproportions are shown in Fig.13.The view letter isplaced to the left, and the angle is placed to the rightof the arc. Character sizes are in accordance with ASMEY14.2.