Basic Technology

Type of Lines in Technical Drawings

Biola Emmanuel - Fri, 05th July, 2019 @ 12:48: PM

Lines in Technical Drawings:

We have various type of lines in technical drawings and geometric constructions. Each of these lines will serve a different purpose by providing a specific detail or information to those looking at your construction or drawing. As a student, an understanding of the various type of lines will prove generally useful, especially to those with great interest in Mathematics and Basic Technology. Also, those who are into buildings (Building Engineers) will need to read and interpret various architectural drawings in order to effectively implement their job.

Lines are used for the interpretation of drawings by the technical people involved.

Type of lines is a form of language communication between technical individuals.


Type of lines

Image Credit: Chegg


1. Thin Continuous Line


A thin continuous line could be a straight or curved line but the main point is that it’s a tiny (thin) line with no dot or dashes within it. A thin continuous line is used for representing the followings:

  • Projection lines
  • Hatching lines
  • Construction lines
  • Short center lines
  • Measurement lines
  • Diagonal lines used to state plane surfaces
  • Intersections
  • Leader lines
  • Backside section lines


2. Thick Continuous Line


It has a stronger outline than the thin continuous line. It could be straight or curved, but with no dot or dashes within it. It is mainly used for:

  • Representing visible Outline and Edges
  • Surrounding the sides that matter in technical drawings


3. Short/Thin Dash Lines


These lines contain short tiny (thin) dashes within it. They are used for:

  • Representing hidden details and edges on an object.
  • Representing hidden outlines.


4. Dashed Thin Lines with Dots

Please see the diagram above

  • They are used for center lines.
  • They are used as line of symmetry.
  • They serve as axis lines of symmetrical drawings.


5. Dashed Thin Lines with Double Dots

This line is similar to the Dash Thin Lines with Dots EXCEPT that it has double dots within it

  • It is used for ghost outlines and bend.


6. Arrowhead Lines

Image Credit: Indezine

They are lines with pointed edges at one or both end (pointed edges are in the form of an arrow). They are used:

  • At the end of dimensional lines.
  • As measurement lines.


7. Continuous Thin Straight Zigzag Line

This is a straight line in the zigzag direction. Please see the diagram above

  • They are used for representing long break lines.
  • They are used for limits of partial views if the limit is not an axis.
  • They are used for limits of interrupted sections if the limit is not an axis.


8. Free Hand Line

These lines are drawn only with the hands and without a ruler or another similar ruling material.

The Free Hand Line is similar in function to the Continuous Thin Irregular Line

The free hand line serves the following:

  • Limits partial views.
  • Interrupts views and sections.
  • Used as the limit to an interrupted view when an axis is not present.


9. Chain Thin Line with Thick Ends

Please see the diagram above

  • They are used on cutting planes

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