Understanding Engineering Drawings
Summary
TLDRThis video script provides an in-depth guide to understanding engineering drawings, essential tools for engineers to communicate design and manufacturing specifications. It covers the different types of drawings, including assembly, detail, layout, and interface control drawings, and their adherence to standards like ASME Y14 and ISO. The script explains the structure of drawings, projection methods, and the importance of views, dimensions, and tolerances. It also touches on advanced concepts like geometric dimensioning and tolerancing (GD&T), and hints at future trends like model-based definition and statistical tolerance analysis. The video aims to equip viewers with the skills to decipher and effectively use technical drawings in engineering.
Takeaways
- 🔍 Technical drawings are essential tools for engineers to communicate design and manufacturing details.
- 📐 There are different types of engineering drawings, such as assembly, detail, layout, and interface control drawings, each serving specific purposes.
- 📜 Drawings follow conventions defined in standards like ASME Y14 and ISO, with companies often having their own requirements.
- 🏢 The title block, usually at the bottom right, contains vital information like company logo, drawing title, number, scale, and author details.
- 👷♂️ Detail drawings provide all the information needed to fabricate and inspect a specific part, without defining manufacturing methods.
- 📈 Primary views, including front, side, and top views, are key to defining a part's geometry in three dimensions through orthographic projection.
- 🌐 Projection methods differ between first angle and third angle projection, with the latter being more common in North America.
- 📊 Additional views like isometric and exploded views can enhance clarity, while sectional views reveal internal geometry.
- 📝 Drawings often include tables, notes, and bills of materials to provide extra information and instructions.
- 📏 Dimensions on a drawing provide all the necessary measurements for part manufacturing, with best practices guiding their placement and presentation.
- ⚙️ Threads are specified using standardized systems like ISO for metric and Unified Thread Standard for U.S. customary units, detailing diameter, pitch, and fit class.
- 🔄 Tolerances define acceptable deviations from nominal sizes and are crucial for part inspection and acceptance, with best practices advocating for as宽松 as necessary.
Q & A
What is the primary purpose of technical drawings in engineering?
-Technical drawings are used to define how a part should be manufactured and inspected, as well as to explain how different parts of a system fit together. They serve as essential communication tools for engineers.
What are the different types of engineering drawings mentioned in the script?
-The script mentions assembly drawings, detail drawings, layout drawings, and interface control drawings. Assembly drawings show how components fit together, detail drawings define the geometry of a single component, layout drawings illustrate a design approach without much detail, and interface control drawings identify interfaces with other components.
What are the common standards that drawings often follow?
-Drawings often follow conventions defined in technical standards such as ASME Y14 and various ISO standards. These standards provide detailed guidelines that companies typically adhere to, with some having their own specific requirements.
What is the general structure of a drawing according to the script?
-A drawing generally has a title block, a revision history table, and the drawing space. The title block is usually located at the bottom right corner and contains important information such as the company logo, drawing title, drawing number, scale, and details about the author, checker, and approver.
Can you explain the concept of primary views in technical drawings?
-Primary views in technical drawings include the front, side, and top views. They are created by projecting the visible edges of the part onto an imaginary plane aligned with the face of the object, a method known as orthographic projection. These views are essential for defining a part in three dimensions.
What is the difference between third angle projection and first angle projection?
-Third angle projection arranges views based on the projection plane being placed between the camera and the object, with the left view placed to the left of the front view and the top view above it. First angle projection places the projection plane behind the object, resulting in the left view being placed to the right of the front view and the top view below it.
What is an isometric view and how does it differ from primary views?
-An isometric view is an additional view that shows the object in three dimensions, which can improve the clarity of a drawing. Unlike primary views, which are aligned and show the object from specific orthogonal directions, isometric views provide a more intuitive representation of the object's shape.
What is the purpose of a bill of materials in assembly drawings?
-A bill of materials in assembly drawings is a table that lists the parts that make up the assembly and the required quantities. It serves as a reference to identify and quantify the components used in the assembly.
What are some best practices to consider when dimensioning a drawing?
-Best practices for dimensioning include placing dimensions outside the part, not using hidden lines for dimensioning unless necessary, avoiding dimensioning 90-degree angles as they can be assumed, and adding centerlines to circular features to aid in dimensioning and clarity.
What is the purpose of geometric dimensioning and tolerancing (GD&T)?
-Geometric dimensioning and tolerancing (GD&T) is a method for applying tolerances that allows for the control of a range of different characteristics such as flatness, roundness, and perpendicularity. It complements traditional dimensional tolerancing by considering the function and shape of an object, not just its size.
What does the script suggest about the future of engineering drawings and design?
-The script suggests that the future of engineering drawings and design may involve model-based definition and statistical tolerance analysis. These topics indicate a shift towards more sophisticated and data-driven approaches in engineering design.
Outlines
📚 Understanding Engineering Drawings
This paragraph introduces the importance of technical drawings in engineering, which serve as essential tools for communication among engineers. It explains that these drawings can define manufacturing and inspection processes, as well as illustrate how system components interact. The video aims to demystify the often complex nature of these drawings. It outlines the various types of drawings, such as assembly, detail, layout, and interface control drawings, and mentions the common standards like ASME Y14 and ISO. The paragraph also describes the general structure of a drawing, including the title block, revision history, and drawing space, and explains the concept of primary views in orthographic projection, highlighting third and first angle projection methods.
📐 Primary and Additional Views in Drawings
This section delves into the specifics of primary views, which include front, side, top, and bottom views, essential for defining a part in a detailed drawing. It uses the example of a bracket to illustrate how these views are created through orthographic projection. The paragraph explains the process of unfolding projection planes to arrange views on a drawing and contrasts third-angle projection, common in North America, with first-angle projection, prevalent in Europe. It also introduces additional views like isometric and exploded views, which enhance the clarity of the drawing, and discusses the use of section views to reveal internal geometry. The paragraph emphasizes the flexibility in layout and the inclusion of tables, notes, and bills of materials in assembly drawings.
📏 Dimensioning and Tolerances in Technical Drawings
This paragraph focuses on the critical aspect of dimensioning in technical drawings, providing the necessary dimensions for manufacturing a part. It discusses best practices for dimension placement, the use of center lines, and the specifics of hole representation, including plain, counterbored, countersunk, and threaded holes. The paragraph explains standardized thread types, such as ISO for metric and Unified Thread Standard for U.S. customary units, and how to specify them. It also addresses the concept of tolerances, which define acceptable deviations from nominal sizes, and the importance of avoiding overly tight tolerances to prevent increased manufacturing and inspection costs. The distinction between chain dimensioning and datum dimensioning is highlighted, with the latter being preferred to avoid tolerance accumulation and facilitate inspection.
🔍 Advanced Tolerance Application and Emerging Trends
This section introduces advanced tolerance application methods like geometric dimensioning and tolerancing (GD&T), which complement traditional dimensional tolerancing by controlling object function and shape characteristics. It mentions feature control frames and how GD&T can control perpendicularity and positional accuracy. The paragraph also touches on the evolution of engineering drawings and design, hinting at the impact of model-based definition and statistical tolerance analysis. It suggests that these topics, although not fully covered in the video, are explored in a companion video available on Nebula, a platform for independent educational creators, and好奇心流, an educational streaming service offering a discount for viewers.
🌟 Conclusion and Additional Resources
The final paragraph wraps up the discussion on engineering drawings, thanking viewers for their attention. It also promotes a bundled offer between Nebula and CuriosityStream, providing a discount for an educational streaming service that includes a wide range of documentaries and exclusive content. The paragraph encourages viewers to take advantage of the offer to access a wealth of informative and engaging material on both platforms.
Mindmap
Keywords
💡Technical Drawings
💡Engineering Drawings
💡Assembly Drawings
💡Detail Drawings
💡Orthographic Projection
💡Title Block
💡Revision History Table
💡Projection Methods
💡Tolerances
💡Geometric Dimensioning and Tolerancing (GD&T)
💡Model Based Definition
Highlights
Engineering drawings are essential tools for communication in engineering, defining manufacturing and inspection processes.
Different types of drawings include assembly, detail, layout, and interface control drawings, each serving specific purposes.
Drawings follow conventions defined in technical standards like ASME Y14 and various ISO standards.
The general structure of a drawing includes a title block, revision history table, and drawing space.
Primary views in a drawing include front, side, and top views, essential for defining a part's geometry.
Orthographic projection is used to create primary views, aligning with the object's face for visibility.
Third angle projection and first angle projection are two common methods for arranging views on a drawing.
Exploded views in assembly drawings illustrate how different parts fit together.
Sectional views provide a detailed look at internal geometry by showing the object as if it's been sliced.
Drawings often contain tables and notes for additional information, such as bills of materials.
Dimensioning in drawings provides all necessary measurements for part manufacturing.
Best practices for dimensioning include placing dimensions outside the part and avoiding hidden lines for dimensioning.
Tolerances define acceptable deviations from nominal sizes and are crucial for part inspection and acceptance.
Chain dimensioning and datum dimensioning are two approaches to applying dimensions, with datum dimensioning often preferred.
Geometric Dimensioning and Tolerancing (GD&T) is a method for controlling shape and function through feature control frames.
Model-based definition and statistical tolerance analysis are emerging topics indicating the future of engineering drawing and design.
Nebula and CuriosityStream offer ad-free educational content and documentaries for a comprehensive learning experience.
Transcripts
technical drawings are everywhere in
engineering they can be used to define
how a part should be manufactured and
inspected or to explain how the
different parts of a system fit together
ultimately they're tools that Engineers
use to communicate so being able to
understand them is an important skill
but it can sometimes feel like they're
quite difficult to decipher in this
video we'll cover everything you need to
know to make sense of them so let's get
started
engineering drawings come in all shapes
and sizes assembly drawings show how all
of the different components of an
assembly fit together and the functional
relationship between them
detail drawings on the other hand fully
Define the geometry of a single
component although they don't normally
Define the manufacturing methods that
should be used they provide all the
information needed to fabricate and
inspect a specific part
other types of drawings include layout
drawings that are used to illustrate a
design approach and so don't include
much detail
and interface control drawings that
identify any interfaces with other
components
drawings often follow conventions that
are defined in technical standards with
the most common being as me y14 and the
various ISO standards
standards go into a lot of detail and
companies usually have their own
requirements anyway so in this video
we'll just cover the fundamentals and
some best practices without focusing on
any one particular standard
regardless of the standard being used
drawings all have the same general
structure
the title block is usually located in
the bottom right corner
it contains important information like
the company logo
drawing title
drawing number
the scale of the drawing and information
about the author Checker and approver
on detail drawings the title block might
also include information about the part
material finish and surface roughness
next there's the revision history table
usually in the top right corner that
lists changes to the drawing
and finally there's the drawing space
which is where views of the component or
assembly are shown
if there are a lot of different views on
the same page it can be confusing but
there's always an underlying structure
to how they're laid out
let's start by looking at primary views
which are the front side and top and
bottom views that are a key part of any
detailed drawing
we'll illustrate how they're drawn using
this bracket
a primary view is created by projecting
the visible edges of the part onto an
imaginary plane that's located between
the part and the Observer and is aligned
with the face of the object
this is called an orthographic projected
View
the orthographic part means that the
projection lines are at right angles to
the plane
one view is chosen to be the front view
this is usually the view that provides
the most information about the object
additional projected views showing its
other sides are then needed to fully
Define the object in three dimensions
this is the view of the left side of the
object
this is the rear view
[Music]
and we can generate the top bottom and
right views in the same way
[Music]
the projection planes are then unfolded
and this is how the views are placed on
a drawing
because the projection plane was between
the camera and the object the left view
ends up being placed to the left of the
front view the top view is placed above
it and so on
only enough views need to be used to
ensure that the part is fully defined
here the right bottom and rear views
aren't needed and can be removed
this way of arranging the views based on
the projection plane being placed
between the camera and the object is
called third angle projection
but there's another common method called
first angle projection where the
projection plane is located behind the
object instead of in front of it
thank you
when this method is used the left view
is placed to the right of the front view
and the top view is placed below it
first angle projection is more commonly
used in Europe and third angle
projection is more common in North
America
to understand why these methods are
called first and third angle projections
consider two perpendicular planes that
create four quadrants
if an object is located in quadrant one
and is being viewed either from above or
from the right the views are projected
onto planes that are behind the object
which is first angle production
but in the third quadrant the views are
projected onto planes that are in front
of the object which is third angle
projection
foreign
showing a tapered cone is used to
indicate which projection method has
been used on a drawing
when drawn using first angle projection
the view from the left where both
circular edges are visible is placed to
the right of the front view
and for third angle projection it's
placed to the left
one of these two symbols is usually
added to the drawing title block
on this drawing of the bracket there's a
third angle projection symbol in the
title block
so we immediately know that the view
above the front view shows the top of
the part
in the view to the left of it shows the
left side of the part
primary views always line up with each
other perfectly which makes it easy to
locate the same feature in different
views
but other views can be added to the
drawing to complement the primary views
and they can be placed anywhere on the
page they don't have to be in alignment
a very common additional view is the
isometric view it shows the object in
three dimensions which can do a lot to
improve the clarity of a drawing
[Music]
assembly drawings sometimes contain just
a single isometric View
a variant on this is the exploded view
which illustrates how the different
parts of an assembly fit together
if a drawing includes small features
that can't be properly shown in the
primary views detailed views showing
them at a larger scale are used
foreign
has internal geometry hidden lines can
be shown on any of the views usually as
dashed lines
but another option is by turning a view
into a sectional view which shows the
object as if it's been sliced
solid areas that have been cut through
or drawn as hatched surfaces and The
Cutting plane and viewing direction are
defined on one of the other views
foreign
of course there's always more than one
way to lay out a drawing it's up to the
author to use the different views in a
way that best presents the important
information
drawings will often contain tables and
notes that provide additional
information
assembly drawings for example usually
include a bill of materials a table that
lists the parts that make up the
assembly and the required quantities
foreign
balloons are added to the drawing to
identify the different parts in the
table
[Music]
notes are used to specify any important
additional information
on assembly drawings this might be
recommended torque ranges for bolts or
instructions to be followed during
assembly
if a note is shown inside a flag it
means it refers to a specific part of
the drawing
on detailed drawings the notes could
include material and coding information
if these haven't been specified in the
title block or information about how
Parts should be marked for example
foreign
pieces of information on a detailed
drawing is dimensions
the drawing should provide all of the
dimensions needed to manufacture the
part which includes lengths
the diameter of holes
or the radii of fillets for example
some features like this fillet are
defined by an arrow and a short string
of text which is called a call out
the same feature appears more than once
in a view it's common to only Dimension
at once
the word typical is sometimes added to
the callout to indicate that the feature
appears several times although the best
approach is usually to explicitly State
how many times it appears
each Dimension is normally only defined
once although redundant Dimensions can
sometimes be shown if it makes the
drawing clear to indicate the total
length of a part for example
these are called auxiliary dimensions
and are enclosed in Brackets to make it
clear that they're provided for
information only
foreign
if you're preparing a drawing there are
quite a few best practices to bear in
mind when it comes to dimensioning
here are a few examples
Dimensions shouldn't really be placed
inside a part
they should always be on the outside
hidden lines shouldn't normally be used
for dimensioning if a specific detail
can only be dimensioned from a hidden
line you should probably be using a
sectional view instead
it's not usually necessary to Dimension
90 degree angles lines that look like
they're at 90 degrees can be assumed to
be right angles
it's a good idea to add center lines to
Circular features Central lines
reinforce the fact that the features are
circular which may not be obvious from a
single View and can be useful for
dimensioning
holes appear in so many drawings that
it's worth discussing them in a bit more
detail
the call out for a plain hole is simple
it needs to include two things the
diameter of the hole and the depth of
the hole
if no depth is specified it's assumed
that the hole goes all the way through
although often this will be stated
explicitly
if a hole is counter bored or
countersunk this will be indicated in
the callout by using the correct symbol
and specifying the diameter and depth or
the diameter and angle as appropriate
things get a bit more complicated when
it comes to threaded holes which are
drawn as two concentric circles that
represent the crest and root of the
thread
the call out has to Define all the
information needed to create the thread
and this is usually done by referring to
one of several standardized thread types
the two most common are the iso standard
for metric units and the unified thread
standard for U.S customary units
the call out for an iso thread starts
with the letter M for metric followed by
the thread nominal diameter in
millimeters and then the letter X and
the thread pitch
the pitch is the distance between
threads
the ISO standards Define preferred
combinations of diameter and Pitch which
includes options for coarse and fine
thread pitches
the call out might also include
information about the thread class of
fit which essentially describes how
tight the fit will be between the two
mating parts
6h and 6G are standard fits with
uppercase or lowercase letters being
used to indicate whether the fit refers
to the internal or external thread
and that's all the threat information
that needs to be specified on the
drawing because everything else is
defined in the ISO standards
the call out for a unified thread
follows a similar approach it starts
with a nominal size which is the
diameter in inches for sizes larger than
a quarter inch or a number from 0 to 12
for smaller sizes
the size is followed by a dash in the
thread pitch which is specified in
Threads per inch instead of as a
distance
next is some text specifying the thread
grade which is usually UNC for coarse
pitch UNF or a fine pitch or unef for an
extra fine pitch
and finally there's the class of fifth
which is a number from one to five that
defines the closeness of the fit
followed by the letter A for an external
thread or B or an internal thread
it's obvious that no part can be
manufactured exactly to a set of
specified dimensions
if we take this drawing and make 10 of
these brackets they'll all have slightly
different sizes
there needs to be a way of defining
what's an acceptable deviation from the
nominal size and that's what tolerances
are used for
there are a few different ways of
applying tolerances to a specific
dimension
there's the limit approach that states
the upper and lower acceptable limits
for the dimension
or the plus and minus approach that
states the acceptable deviations
then there are general tolerances which
are specified in the title block
they apply to any Dimension that doesn't
have an explicitly defined tolerance
a drawing that contains Dimensions but
no tolerances is incomplete
manufactured parts will be inspected and
their Dimensions measured using tools
like calipers or a coordinate measuring
machine depending on the required
accuracy and the measurements will be
compared against the tolerances on the
drawing to determine whether the part is
acceptable
the Golden Rule when it comes to
tolerancing is to avoid specifying
tolerances that are tighter than is
absolutely necessary
this chart shows typical tolerances that
can be achieved for different
manufacturing processes
specifying very tight tolerances will
limit the methods that can be used to
fabricate the part and will result in it
being far more expensive to manufacture
and to inspect
the way a part has been dimensioned can
also have a big impact on tolerancing
and this should be taken into account
when adding Dimensions to a drawing
[Music]
this part has been dimension in two
different ways the method on the left is
called chain dimensioning where
dimensions are applied from one feature
to the next
and the method on the right is called
datum dimensioning where the dimensions
are applied from a chosen feature or
Surface called a datum which in this
case is the left surface of the part
because each Dimension has a tolerance
chain dimensioning can result in an
unwanted accumulation of tolerances
datum tolerancing is often preferred
because it avoids stacking up tolerances
it can also make it easier to inspect
the part since all measurements are made
from the same surface
of course there are scenarios where
chain dimensioning might be the best
approach for example when you want to
control the relative distances between
several holes
the important thing is to think
carefully about how your dimensions and
their tolerances will affect the shape
of the part
the traditional approach to applying
tolerances does have limitations for one
thing it only considers the size of an
object it doesn't consider function or
shape it doesn't allow you to properly
control how flat a particular surface
should be
or how round the cross section of a
cylinder should be for example
geometric dimensioning and tolerancing
is a different method for applying
tolerances that allows you to do exactly
that it complements traditional
dimensional tolerancing by allowing you
to control a range of different
characteristics
[Music]
you'll know if a drawing has used gdnt
because it will contain blocks called
feature control frames that Define these
additional requirements
this feature control frame controls the
perpendicularity of this surface
relative to datum a for example
and this one controls the position of
the center of the hole
if a drawing has Dimensions enclosed in
a box it means that normal tolerances
don't apply to that feature because the
position is controlled using gdnt
instead
g d and T is quite a complex topic that
deserves its own video so I'll cover it
separately on this channel
engineering drawings as we know them
have been around since the time of the
Industrial Revolution and GD T came
along in the 1940s but the established
drawing conventions and the way parts
are designed are slowly changing
two topics that may give us some idea of
where the future of engineering drawing
and design is headed are model based
definition and statistical tolerance
analysis these are particularly
interesting topics I wanted to cover but
they didn't quite fit into this video so
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can watch right now over on nebula where
I explore how model-based design works
and where I cover the basics of
Tolerance Stack Up analysis
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[Music]
and that's it for this look at
engineering drawings
thanks for watching
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