In the process of creating a drawing, an engineer is faced with a whole range of problems, the ability to solve which is the degree of his qualifications. Determining the visibility in the drawings of complex parts is one of the problems mentioned. The most common method for determining visibility in a drawing is the concurrent point method.
Images of a part without definite visibility in at least two main views capturing a front view, for this, a front and top view, marked key points in the drawing, in which visibility will be determined, are better suited
Find points in the drawing, the projections of which on any plane coincide, without coinciding at the same time on another projection plane. Such points are called competing and they will be used by us as reference points when building visibility, informing us about the location of those objects in space to which these points are anchored.
Through the points you marked earlier, intended for determining the visibility, draw lines so that they are perpendicular to one of the main projection planes, while automatically becoming parallel to the other projection plane.
Mark the intersection points of the lines you drew in the previous step with the part. These points will be competing because their projections on one plane will coincide without coinciding on the other plane. If the projections of the points coincide on the frontal plane (P1), then such points are called frontally competing. If the projections of points coincide on the horizontal plane (P2), then such points are called horizontally competing.
Determine your visibility. For frontally competing points, visibility is determined from the top view. The point, the horizontal projection of which is located below, that is, closer to the observer, will be visible in the front view. Accordingly, another point competing with this one will be invisible. For horizontally competing points, visibility is determined from the front view, while the point that is higher than the others will be visible, and all others competing for this point will be invisible.