ASME Y14.3-2003 pdf 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 holein 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 projection 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 in the United States. See Fig. 2.
1.6.2 First Angle Projection. First angle projection places the object between the observer and the plane of projection. This method of projection used in some
countries is herein described, in consideration of the need to interchange engineering drawings in an international market. See Fig. 3.
1.6.3 View Relationships. Note that the orthographic views of the object have the same configuration in both the first and third angle projections, but the placement of the views with respect to one another is different. The visibility of lines is always taken from the observer's point of view. See Figs. 4 and 5.
1.7.2 Removed Views. Under certain conditions it may be impracticable to place a view in its normal aligned position. In this instance, viewing indicators are
used to indicate from where the view was taken, and the view is removed to another location on the field of the drawing. See Fig. 9. Removed views are preferably
shown on the same sheet from which the view has been taken. The removed view is identified using the view letters. The removed view may be drawn at the same
scale as the view from which it is taken, or it may be drawn at a noted scale. It is also permissible to use a combination of numbers and letters for removed view identification.
1.7.3 ldentifying Removed Views. To relate the viewing plane or cutting plane to its removed view, capital letters such as A, B, C, etc., are placed near each arrowhead. The corresponding removed views are identified as VIEW A-A, VIEW B-B, VIEW C-C, etc. View letters should be used in alphabetical order excluding I, O, Q, S, X, and Z. When the alphabet is exhausted, additional
removed views shall be identified by double letters in alphabetical order, as in AA-AA, AB-AB, AC-AC, etc.