Visible outline or object line:
Outline is the outstanding feature in any drawing. These are thick conditions lines and are use to the represent the outline or overall shape of an object. Every edge or surface that is visible is represented by these lines.
Section lines used in engineering drawing :
These are thin continuous lines, uniformly spaced and are used to show a part in section. these lines are usually drawn at an angle of 45° (may e 60° or 30° ) to the horizontal. These lines extend edge to edge of the surface in which these are drawn.
Hidden lines used in engineering drawing :
Shape which cannot be seen, when an object is looked at form an outside viewing position, can be drawn in hidden detail. They are also called dotted lines. They are of medium thickness and made up of short dashes of approximately equal length of about 2mm spaced at equal distance of about 1mm. When a dashed line meets or intersects another dashed line or an outline, their point of intersection or meeting should be clearly shown.
Centre lines used in engineering drawing :
Centre lines are drawn to indicates the axes of cylindrical, conical or spherical objects or details, and also to show the centres of circles and arcs. They are thin and long chain lines composed of alternately long and short dashes spaced approximately 1mm apart. The longer dashes are about 6 to 8 times the short dashes which are about 1.5 mm long for the purpose of dimensioning or to correlate the views they may be extended as required. The point of intersection between two centre lines most always be indicated . Focus lines, extreme positions of moveable parts and pitch circles are also shown by this type of line.
Dimension lines and dimensioning used in engineering drawing :
These lines are continuous thin lines. They terminated at the outer ends by pointed arrow heads touching the outlines, extension lines or centre lines.
Break lines used in engineering drawing :
1) short breaks and irregular boundary lines :
These are thin lines drawn free hand and are used to show a break of an object which extends over a short length of the drawing or to indicate the irregular boundary of an object. these result in a saving in space and time used for drawing without loss of detail.
2) long breaks lines.
These are thin ruled lines having freehand zigzag sat suitable intervals and are used when the break extends over a considerable length of t he drawing.
Extension lines used in engineering drawing :
These lines also are continuous thin lines. They extend by about 3mm beyond the dimension lines.
Header of pointer lines used in engineering drawing :
header line is drawn to connect a note with the feature to which it applies. It is a continuous thin line.