Machine Drawing

16 Machine Drawing

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d:\N-Design\Des2-1.pm5 Seventh Print

2.4.2 Order of Priority of Coinciding Lines

When two or more lines of different types coincide, the following order of priority should be

observed:

(i) Visible outlines and edges (Continuous thick lines, type A),

(ii) Hidden outlines and edges (Dashed line, type E or F),

(iii) Cutting planes (Chain thin, thick at ends and changes of cutting planes, type H),

(iv) Centre lines and lines of symmetry (Chain thin line, type G),

(v) Centroidal lines (Chain thin double dashed line, type K),

(vi) Projection lines (Continuous thin line, type B).

The invisible line technique and aixs representation should be followed as per the

recommendations given in Table 2.5.

Table 2.5A Invisible lines

Instructions Correct Incorrect

Begin with a dash, not with a

space

Dashes intersect without a gap

between them

Three dashes meet at the

intersection point

As a continuation of a visible

line/arc, begin with space

Invisible arcs begin with a dash

Small arcs may be made solid

Two arcs meet at the point of

tangency