Reading an engineering drawing is hard.
It's a foreign language and it takes practice and it takes skill
to know how to read those engineering drawings.
In this particular course,
I know you've been given some complex drawing sets that you need to try to digest.
It can be frustrating and it is definitely difficult.
In this particular video,
I'm gonna take you straight into my iPad and together
we're gonna look around at the engineering drawing for the NES
front cover for the Nintendo game controller for the NES system.
And what I'm going to do is talk through
how to extract essential information
from
the engineering drawing set.
All right,
so just pulling a chair up over here,
looking at the engineering drawing now.
Any time you have an engineering drawing,
you've got to spend time actually reading the engineering drawing
and so what I've what I'm doing right now,
I'm taking a look at a couple of things,
maybe I'll highlight where I'm sort of looking.
First thing I'm doing is I've come down here to
see how many pages or sheets are in this drawing set
that's alerting me to
the extent of the information that I need to be looking for
and through.
I'm also taking a look at what's going on up here with the revision block.
I'm seeing that there was a corrected dimension on a rim groove.
I like to just know what rev I'm looking at and why I'm looking at it.
I
like to start by just sort of glancing through each of the sheets
and understanding what I might be seeing on each of the pages.
In this case,
I
am seeing the front face and I'm seeing the front face again
with a bunch of dimensions here for the whole cutouts,
and then there seems to be this little rim
that goes around this stuff right here,
these seem to be defined in this view.
Right here,
seeing another cross-section and another note.
OK,
on this one, I'm seeing all of the underside
objects
as well as having an ISO view here which is helpful,
so don't have to go all the way back to sheet 1.
I can see that this page is going to be
helping me understand how to create these thin-walled
features that are sort of in these areas.
OK,
and then I see there's at least 3 cross-sections here,
just trying to get a sense for what's in the drawing.
And then here all these screw bosses,
this is a screw boss right here by the way,
all these screw bosses are defined, their location,
their heights,
etc.
And then in the last page of the drawing,
we have this whole,
this whole situation that's going on in detail
'J'
is being defined out
on this sheet.
That's where the cable comes out of the controller.
And so, I've spent about a minute
just glancing through these five sheets.
I have a sense for what's in here.
I haven't absorbed any
deep information yet,
but I have
checked to just sort of see what is there,
OK?
I've also spent a little bit of time glancing at the title block,
particularly in this area,
to understand a couple of things.
This model needs to be created in millimeter units.
The model material
needs to be ABS,
and then there is a texture on it,
MT11010,
and there is a color specification that's given.
So, there's a lot of stuff that's been given right there that's
going to be essential for me as I create this model,
especially as I begin the modeling process,
I've got to absolutely make sure that my units are right,
that can cause a bit of trouble if I'm starting in inches.
And then I need to switch this to millimeters.
The other thing I'm noticing here that's quite helpful for me
is this data right here that shows what the mass
of this finished top cover is.
That's going to be helpful for me as I
analyze my model and go along,
during
the modeling process,
that's going to be helpful
to me.
OK,
so that's the first part of just sort of absorbing
an engineering drawing set is just to
give it a once over,
then we need to start thinking about how to extract out
the essential information that's in this drawing.
Now,
a couple of tips.
Item number 1
is that engineering drawings are often
created in a sort of hierarchical way,
meaning that the top level information is on page 1
and the more detailed information is later
in the process.
So, if you're getting started with your model,
the first CAD modeling steps are likely going to be coming from
the details found in the first couple of pages of the drawing
versus the latter
pages
or sheets in the drawing.
So, for example,
if I was going to start the process of making this model,
I've got to ask myself some key things like
what is the overall width and what is the overall height,
and what is the overall thickness
of this basic prism
that this thing is made of?
Take a look at the drawing now and see if you can extract that out
in a reasonable
way.
What you should be looking for here is
the largest dimension,
here is my length.
My next dimension here is my total sort of height as it would appear in this
or
the width,
I guess we could say
in this view,
and then I have the height or the thickness
of this
overall part shown right here.
These three dimensions are essential for me as I get started in my CAD model
because I'm gonna start by creating
some chunk of material out of which I will cut out a bunch of holes and other stuff
like this
and these three dimensions,
the width.
Excuse me,
the length,
the width,
and the height
are super helpful.
But I can also notice a really important thing that's going on here and that is that
we
have
basically
like
a trapezoidal
prism
in this shape.
In other words,
they do not have
vertical walls.
And this means I'm going to have to start my CAD work in a particular way,
because the first piece that I wanna pop in here
that isn't actually going to be
a rectangular prism,
it's going to be more like a trapezoidal prism,
and I have to start to understand
that shape.
This is what it looks like from the right side,
also from the front view right here,
we're seeing the same thing,
OK,
we're seeing a
trapezoidal
inward sort of
slanting to those walls.
So, this is a really,
really important bit of information to extract from
this drawing set.
Now,
the major question is how much does it slant in?
Well,
we luckily have this detail view right here
that is telling us that something important is going on in this section,
and we can go find that in Detail A.
Let's go find Detail A.
Here's Detail A.
And
Detail A has
some important information and frankly,
we need to step back just a second
and say,
"One of the first things we have to do whenever we start the drawing,
reading,
the drawing,
the
reading of the drawing is we need to really pay attention to the notes.
The notes are there to help,
like,
to guide and to give direction and to help,
you know what
the creator of the drawing wanted you to know.
So, we can see,
for example,
hidden lines are removed for clarity.
OK,
there's a virtual sharp in Detail A that's
interesting because we're looking at Detail A right now,
and there's something about detail A that's being told to us.
General wall thicknesses are shown in section AA.
Well,
here's section AA,
OK?
And section AA is shown as a slice and not a full cross-section.
If it was a full cross-section,
what this would mean
is that we would actually see
the rest of the object here
without a crosshatch,
but we'd be able to see,
you know,
there'd be like posts and some other stuff,
and it
would get quite cluttered.
So, in this case,
for clarity's sake,
section AA was provided as only a slice.
OK,
now what is a virtual sharp?
OK,
we need to go understand what a virtual sharp is. Because a virtual sharp
is appearing in detail A
and this is an important
part of knowing how the trapezoidal prism
geometry should be made.
So, this little thing that we have here,
I'm going to point to it right now before I draw on it,
that little plus that's there
is the virtual sharp.
What this means is
that if this object
did not have a fillet
in its corner,
right up there,
there's a fillet right in there.
It would have a sharp point,
like what we're seeing right over here.
And that sharp point
would be something that could be dimension too.
And when that sharp point goes away,
such as when there's a filet that's added to something like this,
then
a
marker can go right here.
Let's see if I can switch this color
and
make this even more obvious,
OK?
Then a marker can go right there exactly where the sharp point would have been,
therefore
it is called a virtual sharp.
That can be valuable because
if we want to dimension
to that
we can and we do the dimension to
the virtual sharp and that's actually what's going on
right here.
This 0.85 typical
is going to this virtual sharp.
That helps us to know
what size
that trapezoidal prism
is made at.
All right,
so I'm seeing those 3 or 4 critical dimensions that help
me get my first chunk of material into the CAD system.
Once I have that basic chunk of material into the CAD system,
it's a matter of me starting to chip away
at producing
the geometries associated with that.
So,
I
can see that
because there is
some attempt to describe,
I'll switch colors here for a second,
there's some attempt to describe a general wall thickness,
it's most likely that a shell is used
somewhere in this set,
because the shell gives us a nice constant
wall thickness, and I can see that the wall thickness is shown in section AA,
(whereas it's shown),
it's right here.
OK.
If we're going to look at something that's called general.
Then we're gonna look for something that's called typical
because typical 'TYP'
means that
this same thickness
that's here
also exists here, and also exists here, and also exists here, and also exists here, and
here, and here
and
throughout.
It's a little different over here,
but
nevertheless,
everywhere
in those areas, we would have constant wall thickness.
So,
what have I done?
I have gone into my drawing.
I've tried to figure out how am I going to create my first basic shape.
I've looked at the drawing to pick out
the, the dimensions that are most likely the
ones that I need to create that basic geometry.
Now
it's worth knowing
that there's a lot of information here that's not needed yet.
OK,
so I'm trying to build out my basic trapezoidal prism.
There's some stuff I just don't have to worry about,
OK?
I don't have to worry about,
you know,
this dimension,
for example,
or this dimension.
Those are going to come later.
And the reason why this is important is because
there's a lot of information on these drawing sets
and
you have to be able to start to pick out what
is the important information and what is the not important information
for the given step that you're working on.
And if you had a CAD strategy and your CAD strategy looked something like this,
like you're going to
draw one plane and then I'm gonna switch colors here for a second.
You're gonna draw another plane like this,
OK?
And then you are going to extrude between them
and create some sort of trapezoidal prism.
You would need to know how to first draw
one of those sketches and then how to draw the other sketch,
and what those dimensions would be.
So, you're
looking for those in the drawing set.
All right,
now,
what
else
should we say about this,
OK?
It's important to know,
while you are
looking around drawings for particular bits of information,
there's a couple of rules that you should know about.
Number one,
well,
we don't have any hidden lines on this drawing,
and that's actually good for you right now,
but
you should know that
you're not allowed to dimension to hidden lines on drawings.
This is part of the ASME standards.
You're not allowed to dimension to a hidden line,
and that would mean that if I wanted to know,
for example,
how tall is this post?
Can we go look at the isometric view for a
second so we can know what we're talking about.
I want to know how high is that post.
There's only one way for me to know this in this drawing set
and that is that I have to look for a cross-section,
OK?
And so, let's go see if we can find that cross-section.
Well,
there's a cross-section B right here.
OK,
this is cross-section B and there's no post in that one,
so that's not gonna be it.
OK,
here's some other cross-sections here,
but
none of them go through the post I was wanting,
which was that one.
OK.
So that's a little bit
difficult.
See
what else we have going on here.
OK?
"Oh,
here
we go.
Section-F
goes right through the exact post that I want,
and here's section-F.
Right here,
and it is telling me
the height of that post,
the height of that post is 5.68.
All right,
the height of that post is 5.68.
Another thing you should know about drawings
is you're extracting information from drawings,
and that is
that
lines that,
for example,
I'm gonna look right in here,
OK?
Lines that appear to be right angles
are assumed to be right angles,
that's supposed to be 90,
OK.
Lines
that appear to be on the same line
such as this
are actually on the same line.
And these are important things to know about drawing.
So, for
example,
because,
let's see if I can undo that one that I just did,
OK.
The
height of this post
is this much
and the height of that post is also that same amount,
5.68, because they appear to be on the same line,
OK?
Same thing goes with lines that are flat
appear to be flat
are actually flat,
and all that kind of wonderful stuff.
OK,
what else do we need to know about this?
We need to know that
there are some symbols on here that
need to be described.
OK.
This is a complex one,
for example,
OK?
This means that there are 6
features that have a diameter of 1.44,
see if we can think about what that is,
there's 1,
there's 2,
there's 3,
there's 4,
there's 5,
and there's 6.
How do I know that those are the ones?
Because when you come over here and you look at this,
all 6 of those look similar.
OK,
I got to get back to sketching and not erasing
that one,
and that one and that one.
All appear similar. And in this
drawing image they also all appear similar
and the fact that there's a dimension that says 6X
means
that they are.
Now what does this symbol here mean?
This means that there is a hole,
and it's pointing to a hole,
OK,
you can see it pointing right there to that hole.
This hole that's right here
is
5.68 millimeters deep.
Now,
if we couple that together with what we saw in the cross-section,
we can actually see that hole,
it's right there.
OK,
it goes all the way down right there and it
is in line with this.
And so, we know actually that we've interpreted that
correctly.
Let's see if there's anything else in here that's
interesting to talk about right now
other than
the stuff we have already talked about.
I think this is a good one right here.
Let's take a look at this for a minute.
Maybe this drawing has more than one that will help us,
OK,
this is good.
There are two things going on on this drawing that
are on this view that are worth thinking about.
One is the fact that sometimes
8X is used
and sometimes a thing called typical is used.
'TYP' means typical.
Well,
we already know the 8X version of this.
It means that there's 8 radii
of the same exact
size,
and they should be easily pick out a ball
in this drawing.
There's 1,
there's 2,
there's 3,
there's 4,
there's 5,
there's 6,
there's 7,
there's 8.
All 8 of those are 1.3.
But over here,
we have something different going on,
OK?
We don't have
a certain number,
you know,
like 12X or something in front of this 1.00.
We instead just have 1.00 typical.
Why is that the case?
Well,
if we take a look at this guy,
OK,
and let's go erase some of this stuff that I had on here earlier.
OK,
if we look at this guy,
I'm gonna turn this one to blue for a minute.
I've got 1-2-3-4-5-6-7-8-9-
10-11-
12,
but then I also have
this one in red
13-14-
15-16-
17-18-
19-20.
20 geometric features that have a dimension of 1,
just in this particular part of the image.
And so, the way that that's dealt with is not
to say,
well,
what number did I say?
I don't know,
is it 16.
No,
it was 20.
It's not to do this.
But instead,
it's to say 1.00 TYP.
Because it's more obvious that that's what's going on
in this area.
OK,
erasing those.
All right,
what
else do we need to talk about?
It's important to know that circles
will always be designated
by the standards as a diameter and arcs,
not complete circles,
will always be designated by a radius.
It's also important to know that in engineering drawings,
according to the standards,
circles will only be dimensioned where they look like a circle.
So, if I had a shaft,
for example,
that looked like this,
and I had an engineering drawing that looked like this,
I would dimension this one
in this view,
not
like this.
OK,
this one is diameter something.
This is no good.
And the reason why I'm telling you that is because as you look for information,
you want to make sure
that you
are
looking in the right spot.
So, if you're looking for the dimension of a circle,
look where it actually appears
like
a circle.
OK,
a few things I want to just go over here for a second.
As you're trying to extract out the information from these drawings,
(let me just zoom out here for a second).
We want to start
by getting an overall view of the drawing by just scanning through it,
understanding what images are there,
trying to absorb a little bit of stuff,
OK?
We want to take a look at the title block,
see what information is given there.
We definitely want to read the notes,
OK?
And then we want to start getting the top level information
that will help us
to start building out the geometry.
OK.
While
you're doing this,
you want to learn to look for clues
in the drawing,
and I don't mean this from an educational perspective.
I just mean that there are certain things like
general wall thickness that's going to tell you
there's going to be a shell somewhere,
right?
Or
there are
things like these virtual sharps that we saw here that mean that
really we're trying to give a dimension before a radius would occur in a CAD model,
right,
or before a radius occurred in a manufacturing
step.
Also,
we
want to take a look at the cross-sections.
We want to know that the cross-sections are there to help us
and we want to really try to absorb the cross
sections and understand what's going on with the cross-sections.
Then we want to do our best to soak in the details
of the detail view,
right?
What is this telling us?
This is an interesting one right here,
OK?
Because
this line
and this line
are parallel to each other and this line and this line are parallel to each other.
This is interesting because
there are other ways
to
have measured this.
Yeah,
we did this one and this one,
OK?
We could have measured like this,
and these give us two different numbers actually,
and this is something that can cause trouble in this particular
model.
So,
understand
what
these things are telling you,
OK?
Also,
most
important,
I think as you're looking through these engineering drawings is just to realize
that the information is there.
You don't need all of it at once.
You need to use your CAD strategy
to help you know just what bit you need,
what feature you want to create so that you can get into this
set of drawings and go find the essential
dimensions
that will help you get it.
So, I'm coming back now to
just sort of end of this and say that it
is indeed really hard to read these engineering drawings.
It is a foreign language in my view
and it takes practice.
It takes
patience
and it takes a willingness
to actually read them,
and to try to
see what they're telling you, and to envision the geometry
that's being described.
And as you do that,
your mind will be able to
notice certain dimensions,
certain features,
certain patterns,
certain other things
that will help you
during the CAD modeling process.