BluePrint Reading Technical Drawings

1. Blueprint Reading

2. Lesson Objectives
• Locate the title, and revision blocks on a blueprint and
state the information given in them.
• State the information given in the bill of material.
• Explain the purpose of the notes, specifications and legend
found on a blueprint.
• Identify common symbols and abbreviations found on
blueprints.
• Locate a particular point on a print using zone numbers.
• State the purpose of lines, dimensions and scale on
blueprints.
• Identify different views used in blueprints.

3. What is a blueprint?
• Blueprints are reproduced copies of
drawings used to represent clearly
understood pictures of objects,structures,
and systems. Basic information relevant to
the item shown on the print is found in the
title, revision and application blocks.

4. Location and Parts of the title
block
• The title block is usually located in the
lower right hand corner and contains:
– The drawing number.
– Name or part of the assembly.
– Basic required information.
– Name of preparing organization.
– Scale

5. Location/Parts of a title block
(Cont)
– Drafting record
– Authentication
– Preparation date of print.
– Reference numbers to identify the numbers of
related blueprints, modified or improved parts,
or to indicate right- or left-handed parts of an
assembly.
– Number of sheets enclosed.

6. Title Block

7. Revision Block
• The revision block is usually located in the
upper right hand corner.
• It includes a record of changes to the
original drawing. A revised print is
indicated by adding a letter to the original
number.

8. Revision Block

9. Application Block
• Located near the title block.
• Identifies directly or by reference the larger
units of the detailed part on the drawing
forms a component.

10. Application Block

11. Zone numbers
• Zone numbers on a blueprint are like grid
references on a map. To locate a particular
point on a print:
– Locate each zone number on the borders.
– Trace an imaginary line from each number
toward the opposite side.
– The area where the two lines meet gives you
the location of the point.

12. Bill of Material
• A list of parts or materials required by or
used on the blue print. Not only does the
bill of material list the material used, but it
also gives a description of the item.
( Weight, thickness, quantity, milspecs and
other applicable information.)

13. Bill of Material

14. Lines and Symbols
• To properly read blueprints, you must be
familiar with the lines and symbols used on
a blueprint. Various types of lines are used
to show different objects and their
positions.

15. Symbols and Abbreviations
• Symbols and abbreviations have been
developed to simplify blueprint reading.
• Refer to the appropriate technical
documentation as aids in identifying
abbreviations and symbols on blueprints.
• Symbols found on piping prints include:

16. Symbols (Cont)
– Pipe fittings-type of connections
– Elbows
– Tees
– Other pipe fittings
– Valves-types of connections
– Valve types
– Strainers
– Traps

17. Symbols (Cont. 2)
– Power and heating plant equiptment
– Gages, thermometers, and miscellaneous
– Refrigeration equiptment
– Pipeline Symbols

18. Piping Symbols

19. Piping Symbols 2

20. Abbreviations
• Some abbreviations commonly found on
piping blueprints include:
• Welding process abbreviations.
• Cutting process abbreviations.

21. Welding Process Abbreviations
• AAW AIR-ACETYLENE WELDING
• SAW SUBMERGED ARC WELDING
• CAW CARBON-ARC WELDING
• RSW RESISTANCE-SPOT WELDING
• RSEW RESISTANCE-SEAM WELDING
• SMAW SHIELDED METAL-ARC
WELDING

22. WELDING PROCESS (CONT)
• AU AUTOMATIC
• ME MACHINE
• MA MANUAL
• SA SEMI-AUTOMATIC

23. Cutting Process
• AAC AIR-CARBON-ARC CUTTING
• AC ARC CUTTING
• AOC OXYGEN-ARC CUTTING
• CAC CARBON -ARC CUTTING
• PAC PLASMA-ARC CUTTING

24. Notes or Specifications
• Notes or specifications on a blueprint provide
additional information about a drawing or
assembly.
• Notes clarify specific objects.
• Leader lines point out the exact part being noted.
• Specifications provide a description of particulars
or objects shown on a print and describe
performance requirements and items to be
obtained or maintained.

25. Lines
• Lines are used to indicate the shape of an
object, the limit of dimensions, and to form
blueprint symbols. Line characteristics such
as width, breaks, inline, and zigzags have
special meanings.

26. Lines used in Blueprints

27. Lines (Continued)

28. Dimensions
• Dimensions indicate size and location. They
are indicated by whole numbers, fractions,
decimals, or angles. Dimensions are also
used to outline shapes of objects on
drawings and prints. There are six major
kinds of dimensions:

29. Six Major Dimensions
• (1) Conventional dimensions give the
overall dimensions, length, width, and
height of an object.
• (2) Baseline dimensions give all the
dimensions of an object and are indicated in
relation to a designation baseline or
centerline. Baseline dimensioning is used to
mark precision parts on a drawing or print.

30. Six Major Dimensions (cont)
• (3) Chamfer and bevel dimensions are used
to indicate the linear and angular
dimensions of the edges of an object.
• (4) Radius and arc dimensions are used to
indicate circular or rounded portions of
objects

31. Six Major Dimensions (cont)
• (5) Drilled hole dimensions are shown on a
print by using a leader and a note. The
leader indicates the location of the hole; the
note lists drill size, the number of holes to
be drilled, and usually the depth of the hole
to be drilled. If the depth is not given, the
hole is to be drilled completely through the
object.

32. • (6) Tolerance dimensions represent the
amount by which a dimension can vary and
remain within the limits of the
specifications. Tolerances are indicated by a
plus/minus symbol _ . For example _ 1/2
inch means that the specifications allow for
a variation of 1/2 inch more or less than the
basic dimension.
Six Major Dimensions (cont)

33. Size and Location Dimensions

34. Conventional and Baseline
Dimensions

35. Chamfer and Bevel Dimensions

36. Radius and Arc Dimensions

37. Views
• Orthographic Views
• Section Views
• Developed Views
• Detail Drawing and Assembly Print

38. Orthographic Projection
• An orthographic projection shows the form
of an object by presenting various views
that have either horizontal or vertical
alignment. These views are arranged in a
particular order to present an accurate
picture of the object.

39. Orthographic View

40. Section Views
• Section views give a clearer picture of the
interior of an object or of a hidden feature
that is not visible in conventional outside
views. Section views are made by cutting
away part of the object along a given
cutting plane. Full section (cross section)
and half section views are the most
commonly used in drawings.

41. Section Views (cont)
• A full section ( cross section) shows an
object as if it were cut completely through
along a certain plane.
• A half section is used when the object to be
shown is symmetrical in both inside and
outside details. Only half the object is
sectioned; the other half is shown as a
standard view.

42. Section Views

43. Developments
• Developments are special views used to
show the fabrication of parts from sheet
metal. Development (pattern making or
stretchout) is the method used to make a
pattern.

44. Developed View

45. Detail Drawing and Assembly Print

46. Summary
• Location of title, revision, and bill of material blocks and
information contained therein.
• How to locate a particular point on a blueprint using zone
numbers.
• Identifying common symbols and abbreviations found on
blueprints.
• Explanation of the purpose of notes, specifications, and
legend found on blueprints.
• Explanation of the purpose of lines, dimensions and scale
on blueprints.
• Identification of different views used in blueprints.