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Alphabet Of Lines

Introduction - Alphabet of Lines

! To better understand an engineering drawing, there must be good contrast between the different kind of lines.

! Each line type has a definite form and line weight or thickness.

! Each line type has a different purpose and communicates a different meaning to the person reading the drawing.

Main Line Types

! Visible Object Lines ! Hidden Lines ! Center Lines ! Section Lines ! Dimension Lines ! Extension Lines ! Leader Lines

! Cutting Plane or Viewing Plane Lines

! Break ! Phantom

Visible Object Lines

! Thick, dark solid lines. ! Shows the outline and shape of an

object. ! Defines features (edges and details)

you can see in a particular view.

Hidden Lines

! Thin, short dashed lines. ! Shows the outline of a feature that can

not be seen in a particular view. ! Used to help clarify a feature, but can

be omitted if they clutter a drawing.

Center Lines

! Thin line consisting of long and short dashes.

! Shows the center of symmetrical features such as of holes, round objects or slots.

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Section Lines

! Thin lines usually drawn at a 45 degree angle.

! Indicates the different materials of an object that has been cut through in a sectional view.

Section Lines

Center Line

Dimension Lines

! Thin lines. ! Shows the size of a feature of an

object. (example: length, width, height, diameter.)

! Terminated with arrowheads at the end.

Extension Lines

! Thin lines. ! Used to show the starting and stopping

points of a dimension. ! Must have at least 2mm space between

the object and the extension lines.

Extension Line

Dimension Line

Leader Lines

! Thin lines. ! Used to show the dimension of a

feature or a note that is too large to be placed beside the feature itself.

Leader Line

Cutting / Viewing Plane Lines

! Thick broken line that terminates on both ends with short 90 degree arrowheads.

! Shows where a part is cut in half to better see the interior detail.

Break Lines

! Used to shorten a view or eliminate repetitive details.

! Two types of break lines with different line weights.

! Short Breaks. ! Long Breaks.

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Short Break Lines

! Thick wavy line. ! Used to reduce the length of an object

to a feasible length that can fit on a page.

Long Break Lines

! Long, thin lines. ! Used to show that the middle section of an

object has been removed so it can be drawn on a smaller piece of paper.

! Mainly used for architectural design.

Phantom Lines

! Thin lines made up of long dashes alternating with pairs of short dashes.

! Three purposes in drawings. 1. To show the alternate positions of moving parts. 2. To show adjacent parts that fit together. 3. To show repeated detail.

Alternate Position

! Phantom lines can show where a part is moving to and from.

! Eliminates the confusion of thinking there may be 2 parts instead of just 1.

Phantom Lines

Relationship of Adjacent Parts

! Phantom lines can also show how two or more adjacent parts go together without having to draw and dimension both parts.

Repeated Detail

! Phantom lines can show repeated detail of an object.

! Saves the drafter time.

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Summary

! Now that we have discussed the 10 main line types, you should be able to do the following:

1.  Identify the alphabet of lines. 2.  Identify where the line types are

used. 3.  Produce the lines by hand as part

of technical drawings.