ALPHABET OF LINE
1. OBJECT OR VISIBLE LINES –
THICK DARK LINE USED TO SHOW
OUTLINE OF OBJECT, VISIBLE
EDGES AND SURFACES.
CONTINUOUS AND THICK (0.5 - 0.6
MM).
2. CONSTRUCTION LINE – VERY
LIGHT AND THIN LINES USED TO
CONSTRUCT LAYOUT WORK.
3. DIMENSION LINE – THIN AND
DARK LINES ARE USED TO SHOW
THE SIZE (SPAN) OF AN OBJECT
WITH A NUMERIC VALUE. USUALLY
TERMINATES WITH ARROWHEADS
OR TICK MARKINGS. THE LINE TYPE
IS CONTINUOUS AND THE LINE
WEIGHT IS THIN (0.3 MM).
4. HIDDEN LINE – SHORT DASH
LINES USED TO SHOW NON VISIBLE
SURFACES. USUALLY SHOWN AS
MEDIUM THICKNESS. DASHED AND
MEDIUM THICK (0.35 - 0.45 MM).
5. CENTER LINE – LONG AND SHORT
DASH LINES. USUALLY INDICATES
THE CENTER OF HOLES, CIRCLES
AND ARCS. LINE IS THIN AND DARK.
LONG DASH – SHORT DASH AND
THIN (0.3 MM).
6. EXTENSION LINE – THIN AND
DARK LINES ARE USED TO SHOW
THE STARTING AND ENDING OF
DIMENSION. THE LINE TYPE IS
CONTINUOUS AND THE LINE
WEIGHT IS THIN (0.3 MM).
7. CUTTING PLANE LINE – EXTRA
THICK LINES USED TO SHOW
CUTAWAY VIEWS OR PLANE OF
PROJECTION WHERE A SECTION
VIEW IS TAKEN. ARROW INDICATES
THE DIRECTION OF VIEW. THE LINE
TYPE IS PHANTOM AND THE LINE
WEIGHT IS VERY THICK (0.6 TO 0.8
MM).
8. SHORT AND LONG BREAK LINES
–SHORT AND LONG MEDIUM LINE
USE TO SHOW CUTAWAY VIEW OF A
LONG SECTION. THE LINE TYPE IS
CONTINUOUS AND THE LINE
WEIGHT IS USUALLY THICK (0.5 – 0.6
MM).
9. LEADER LINE – MEDIUM LINE
WITH ARROWHEAD TO SHOW
NOTES OR LABEL FOR SIZE OR
SPECIAL INFORMATION ABOUT A
FEATURE.
10. PHANTOM LINE – LONG LINE
FOLLOWED BY TWO SHORT DASHES
USED TO SHOW ALTERNATE
POSITION OF A MOVING PART. THE
LINE TYPE IS LONG DASH – SHORT
DASH – SHORT DASH AND THE LINE
WEIGHT IS USUALLY THIN (0.3 MM).
11. SECTION LINE – MEDIUM LINES
DRAWN AT 45 DEGREES USE TO
SHOW INTERIOR VIEW OF SOLID
AREAS OF CUTTING PLANE LINE.
THE LINE TYPE IS USUALLY
CONTINUOUS AND THE LINE
WEIGHT IS THIN (0.3 MM).
ORTHOGRAPHIC AND ISOMETRIC
PROJECTION
CREATING ORTHOGRAPHIC PROJECTION FROM AN ISOMETRIC VIEW
1. CHOOSE A FRONT VIEW. THIS IS THE VIEW THAT SHOWS THE MOST ABOUT THE
OBJECT.
2. DECIDE HOW MANY VIEWS ARE NEEDED TO COMPLETELY DESCRIBE THE
OBJECT. IF YOU ARE UNABLE TO DETERMINE WHICH VIEWS WILL BE NEEDED,
DRAW THE STANDARD VIEWS (FRONT, TOP AND RIGHT SIDE).
3. DRAW THE VISIBLE FEATURES OF THE FRONT VIEW.
4. DRAW PROJECTORS OFF OF THE FRONT VIEW HORIZONTALLY AND
VERTICALLY IN ORDER TO CREATE THE BOUNDARIES FOR THE TOP AND RIGHT
SIDE VIEWS.
5. DRAW THE TOP VIEW. USE THE VERTICAL PROJECTORS TO FILL IN THE VISIBLE
AND HIDDEN FEATURES.
6. PROJECT FROM THE TOP VIEW BACK TO THE FRONT VIEW. USE THE VERTICAL
PROJECTORS TO FILL IN ANY MISSING VISIBLE OR HIDDEN FEATURES IN THE
FRONT VIEW.
7. DRAW A 45° PROJECTOR OFF OF THE UPPER RIGHT CORNER OF THE BOX THAT
ENCLOSES THE FRONT VIEW.
8. FROM THE TOP VIEW, DRAW PROJECTORS OVER TO THE 45° LINE AND DOWN
IN ORDER TO CREATE THE BOUNDARIES OF THE RIGHT SIDE VIEW.
9. DRAW THE RIGHT SIDE VIEW.
10. PROJECT BACK TO THE TOP AND FRONT VIEW FROM THE RIGHT SIDE VIEW
AS NEEDED.
11. DRAW CENTERLINES WHERE NECESSARY.
CREATING ISOMETRIC PROJECTION FROM ORTHOGRAPHIC VIEW
1. LIGHTLY DRAW CROSS AXES WITH 30° FROM THE LOWER EDGE OF THE PAPER
AS GUIDELINES
2. BASED ON THE ORTHOGRAPHIC PROJECTION’S DIMENSION, PLOT THE HEIGHT
ON THE VERTICAL AXIS (SIMILAR DIMENSION WITH THE VERTICAL AXIS ON
ORTHOGRAPHIC VIEW), WIDTH ON THE LEFT 30° AXIS AND DEPTH ON THE
RIGHT SIDE OF THE 30° AXIS.
3. DRAW THE DETAILS OF THE FIGURE BY ANALYZING AND DETERMINING THE
POINTS IN RELATION TO OTHER POINTS REPRESENTING THE CORNERS,
SURFACES, AND EDGES
4. CHECK THE ACCURACY OF THE DRAWING
5. DARKEN THE LINES BY TRACING WITH HEAVIER LINES.
6. LABEL THE ISOMETRIC PROJECTION
DIMENSIONING
A DIMENSION IS FOR SIZE AND POSITION (OF THE DESIGNED/MODELED SHAPE).
A DIMENSION IS A NUMERICAL VALUE EXPRESSED IN APPROPRIATE UNITS OF
MEASUREMENT AND USED TO DEFINE THE SIZE, LOCATION, ORIENTATION, FORM OR
OTHER GEOMETRIC CHARACTERISTICS OF A PART.
SCALING
A SCALE IS DEFINED AS THE RATIO OF THE LINEAR DIMENSIONS OF THE OBJECT AS
REPRESENTED IN A DRAWING TO THE ACTUAL DIMENSIONS OF THE SAME.
DRAWINGS DRAWN WITH THE SAME SIZE AS THE OBJECTS ARE CALLED FULL SIZED
DRAWING. IT IS NOT CONVENIENT, ALWAYS, TO DRAW DRAWINGS OF THE OBJECT TO
ITS ACTUAL SIZE. E.G. BUILDINGS, HEAVY MACHINES, BRIDGES, WATCHES,
ELECTRONIC DEVICES ETC. HENCE SCALES ARE USED TO PREPARE DRAWING AT
• FULL SIZE
• REDUCED SIZE
• ENLARGED SIZE
TYPES OF SCALE
ENGINEERS SCALE - THE RELATION BETWEEN THE DIMENSION ON THE DRAWING AND
THE ACTUAL DIMENSION OF THE OBJECT IS MENTIONED NUMERICALLY (LIKE 10 MM =
15 M).
GRAPHICAL SCALE - SCALE IS DRAWN ON THE DRAWING ITSELF. THIS TAKES CARE OF
THE SHRINKAGE OF THE ENGINEER’S SCALE WHEN THE DRAWING BECOMES OLD
● PLAIN SCALE
● DIAGONAL SCALE
● VERNIER SCALE
● COMPARATIVE SCALE
SECTIONING
A SECTIONAL VIEW OR A SECTION LOOKS INSIDE AN OBJECT. SECTIONS ARE USED
TO CLARIFY THE INTERIOR CONSTRUCTION OF A PART THAT CANNOT BE CLEARLY
DESCRIBED BY HIDDEN LINES IN EXTERIOR VIEWS. BY TAKING AN IMAGINARY CUT
THROUGH THE OBJECT AND REMOVING A PORTION, THE INSIDE FEATURES MAY BE
SEEN MORE CLEARLY.
RULES OF SECTIONING
RULE 1: A SECTION LINED AREA IS ALWAYS COMPLETELY BOUNDED BY A VISIBLE
OUTLINE.
RULE 2: THE SECTION LINES IN ALL AREAS SHOULD BE PARALLEL. SECTION LINES
SHOWN IN OPPOSITE DIRECTIONS INDICATE A DIFFERENT PART.
RULE 3: ALL THE VISIBLE EDGES BEHIND THE CUTTING PLANE SHOULD BE SHOWN.
RULE 4: HIDDEN FEATURES SHOULD BE OMITTED IN ALL AREAS OF A SECTION VIEW.
EXCEPTIONS INCLUDE THREADS AND BROKEN OUT SECTIONS.
TYPES OF SECTIONAL VIEWS
1. FULL SECTIONS
2. OFFSET SECTIONS
3. HALF SECTIONS
4. BROKEN-OUT SECTIONS
5. REVOLVED SECTIONS
6. REMOVED SECTIONS
7. AUXILIARY SECTIONS
8. PHANTOM SECTIONS