WEBVTT

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>> This lecture is
about adding text

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and dimensions to our drawings.

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Starting with adding text,
some basic rules are,

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we want it to be as
simple as possible.

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In order to do that we
use the TXT font style.

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And all drying notes are
added in capital letters.

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So nothing fancy; easier
and simpler is better.

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The minimum text height
should be .125 inches

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or three millimeters
in the final print out.

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And the text height
in the drawing notes

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and the text height

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of all dimensions should
be equal to each other.

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Notes and dimensions
should be placed outside

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of the part geometry so
that it doesn't interfere

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in the drawing itself and
confuse your audience.

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Now, some dimensioning
terminology:

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a dimension is a numerical value
that defines either the size

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or position or geometric
characteristics

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of a feature in a drawing.

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One type of dimension
is term basic dimension.

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It's one in which it is given
a theoretical exact size

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of the feature.

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Of course that's only--
that's an idealization.

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The basic dimension is
indicated by a box around it.

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Here's an example
of a dimension.

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It's showing the width
of this feature here.

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Here's an example of
a basic dimension.

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It's showing this height here
but we indicate that it's basic

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by putting a box around
the number itself.

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A dimension line
is the thin line--

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thin, solid line
which shows the extent

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and direction of a dimension.

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Dimension lines are
broken for insertion

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of dimension numbers
right in the middle.

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So there's an example here.

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Here's the dimension line
and here's the dimensions.

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There's two numbers here
because it indicates tolerance.

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So an extension line also known

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as a witness line is a thin
solid line perpendicular

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to a dimension line
used to indicate

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which feature is associated
with a given dimension.

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And there should be a visible
gap between the feature

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that you're to mention
and the end

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of the extension
or witness line.

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So the audience doesn't
get confused

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between what are object
lines in the drawing

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and what are extension lines.

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So here's an example of a
long extension line, okay.

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It's pointing to this feature
here being dimensioned,

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and notice that there is
a visible gap in all of--

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here's another dimension
line; there's a visible gap.

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Leader line is a thin solid line
used to indicate the feature

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with which a dimension, note,
or symbol is associated.

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Sometimes instead of using
a dimension line we use a

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leader line.

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Here's an example
here of a leader line.

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It's a dimension
for the diameter

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of this small circle here

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and this arrow here is
called a leader line.

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The phi, the Greek letter phi,

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in front of the dimension itself
indicates that it's a diameter.

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Other terminologies: arrows,
of course we use arrows

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that are placed at the
ends of the dimensions

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to show the limits of the
part we're dimensioning.

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The arrow should be uniform
in size and of the same style.

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You notice that all dimensions
here have arrows pointing

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towards the dimension line.

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Tolerance is the amount a
particular dimension is allowed

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to vary.

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So as opposed to
a basic dimension

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which is theoretically
exact, okay,

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sometimes we indicate tolerance,
meaning that it can vary

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within certain limits.

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Here's an example
of a tolerance here.

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So it's saying here that the
dimension here is acceptable

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as long as it's between
a minimum of 2.490

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and a maximum of 2.510.

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That's an example
of a tolerance.

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And that's an example
of what's called a limit

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of size tolerance.

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You indicate the largest and
the smallest acceptable size

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of that feature as opposed to
a plus and minus dimensioning,

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another method of
indicating tolerance.

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Okay, and you give
a positive allowable

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and a negative allowable
variance

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from a target specified
dimension.

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Here's an example of a plus
and minus dimensioning.

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The target is 1.250, and
the positive error is .032

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and a negative error is .01.

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What that means is that this
part here, this dimension here,

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which to the location
of the center

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of the circle here
is acceptable as long

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as it's not smaller
then what's that,

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1.24 and not bigger then 1.283.

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I'm just adding and
subtracting this positive

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and negative errors.

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The datum is a theoretically
exact point used

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as a reference for dimensioning.

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A technical datum dimensioning
or baseline dimensioning is one

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in which all the dimensions

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and positions are
calculated relative

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to an origin point
defined by datum.

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Here is an example of datum
or baseline dimensioning.

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Here's the origin, so
here's one datum here

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for vertical dimensions
here's another datum here

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for horizontal dimensions.

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And take note all dimensions are
referred to these two datum's.

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Some illustrations regarding
the height of dimensions,

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it should be at least .125
inches if you're going to do it

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by hand, make sure that it's--

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you can use horizontal
guidelines for hand drawings.

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There's not enough room
for both the dimension line

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and the dimension itself, I
can put the arrows outside,

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or you can put the arrows
inside and the dimension outside

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or if it's really really
small, both the arrows--

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both the dimension lines and
the dimensions could be outside.

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Similarly for millimeters,

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looks like the minimum
height is three millimeters

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in the final print out drawing.

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Size and location dimensions
are used to describe the size

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of parts and locations of
features within the parts.

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So of course the
dimensions we're talking

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about are the depth, the
width and the height.

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And location would be
locating say, centers of--

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center lines for circles.

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Staggering the dimension
text illustrated here,

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these are dimensions--
diameter dimensions.

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Very important-- okay you want

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to put the dimensions
outside the part geometry.

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Look at all these dimension
lines inside the boundary

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of the drawing.

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Okay, you don't want that
because the arrows here,

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the dimensions, will interfere
with the drawing itself,

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so you indicate that the
dimensions outside the part

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geometry and notice
again, the extension lines

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or the witness lines that
indicate the locations

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that you are trying
to dimension,

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and notice the visible
gaps as well.

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For repeated dimensions,
such as this,

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instead of dimensioning all
four of the small circles,

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you can use the X.
4X; diameter .375,

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that means that the diameter of
appears in these for circles.

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Regarding detailed
dimensioning, some rules.

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Diameter is specified for
holes and blind holes.

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A blind hole is one that
does not go through, okay,

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if you don't specify
the depth, okay,

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the assumption is it's a true
hole; the hole goes all the way.

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So if it's not-- if
it's a blind hole,

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you have to specify the depth
of the hole by using the depth.

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Drilling operations, okay,
pertain to counterbores

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and countersinks and
spotface as well.

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A counterbore symbol is placed
before the diameter callout,

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and the depth of the counterbore
is added with a depth symbol.

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So these are two examples of
holes that are not true holes.

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Okay, if the depth's
stated, it's a counterbore.

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If it's not, it's a spot face.

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Okay, so if you look at the
way to dimension a counterbore,

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it should show the diameter
of the true hole followed

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by the diameter of the
counterbore and then

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to that of the counterbore.

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Here's an illustration
for the counterbore.

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Here's the counterbore
symbol, and here's an example

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of a counterbore, and here's the
front view of the counterbore.

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So basically, it's too
circles in the top view, right,

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the outer circle
is the counterbore,

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and then you have a smaller
circle that is a true hole.

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Instead of dimensioning the
depths here, or the heights here

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in the front view, it indicates
the depth of the counterbore,

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we collect all of the pieces

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of information regarding
the geometry

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of this counterbore
by using three parts.

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With a leader, okay,
pointing to the counterbore,

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the first line here is the
diameter of the true hole,

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which is the smaller one,
counterbore symbol, okay,

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than the diameter of the outer
circle, the bigger circle,

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and then the depth symbol.

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So this is the depth
symbol here.

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All right, and I
will show you how--

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where you can find
these symbols--

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the counterbore and
the depth as well

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as the countersing symbol
in AutoCAD.

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On the other hand,
for the countersink,

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here is the cross-section
of a countersink.

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They look similar from the
top, but they're really not.

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So for the countersink, you
use the countersink symbol

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to indicate the diameter
followed

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by the angle specifications.

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You don't give the depth because
the depth will be determined

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by the outer diameter and
the angle of the countersink,

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so here's an illustration here.

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You have two circles
here, the diameter here is

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for the smaller diameter is
for the middle two holes,

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so that's 10, and here's
the countersink symbol.

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And the second diameter symbol
is for the outer circle,

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the countersink,
and then instead

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of indicating the
steps here, down here,

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we indicate the angle,
and that's the angle

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between in the front view you
just line here and this line.

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So the depth here will turn
out to be what it is based

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on the given diameters and
the angle of the countersink.

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So if you think about drilling
operations, this angle here

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of 90 will determine how
deep this countersink is

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from this elevation
here to this elevation.

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So no need to indicate
the depth.

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The spotface is very
similar to a counterbore.

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So instead of having to capture
all the little details here

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in the front, regarding
the size and configuration

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of these two drills
here, we capture them

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in one counterbore symbol here
and countersink symbol here.

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Here is an illustration
of another blind hole.

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That means this hole here
doesn't go all the way through.

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If it doesn't go
all the way through,

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you have to indicate
the depth here.

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That's the depth.

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Otherwise, if you indicate this
depth here, it would be assumed

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that this hole is a true hole;
it goes all the way through.

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These are the diameters of all
of these concentric circles,

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okay, and we tried to stagger
the X of the dimensions.

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Avoid over dimensioning okay,

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because an over-dimensioned
part might confuse

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whoever is trying to
manufacture this part.

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And so here's an example here.

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You indicate this with A,
and indicate the width,

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B. You don't need to indicate
the difference between the A

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and B here which is
this dimension here,

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because chances are
both A and B are going

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to be slightly in error.

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Which means that B
minus A is not going

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to be exactly what this is.

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If you remember, manufacturing
operations are subject to error.

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So say if I indicate the exact
value of A here, and the value

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of B here, and also indicate
C, that's going to be

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over determined, and if
A and B are in error,

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A plus B is not necessarily
going to be equal to C. Okay.

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Also, when deciding where
to show a dimension,

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you select the view that
is most descriptive.

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So we're trying to indicate here
in this example in the height

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of this part of the L. Okay,
and it's preferred to mention it

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in this view, right, because
you can clearly see that this is

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for the lower part of the
L rather this one here.

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So this one is technically
not wrong,

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but putting the dimension
here is preferred.

00:13:21.846 --> 00:13:24.996 A:middle
Some-- I'll summarize
some fundamental rules

00:13:24.996 --> 00:13:25.956 A:middle
of dimensioning.

00:13:25.956 --> 00:13:28.586 A:middle
You will need size
and dimensions

00:13:28.636 --> 00:13:32.266 A:middle
to indicate length width,
height, or with depth

00:13:32.266 --> 00:13:35.466 A:middle
and height, as we called them
before, as well as diameters

00:13:35.466 --> 00:13:37.896 A:middle
of circles and radii of arcs.

00:13:38.026 --> 00:13:40.826 A:middle
So if it's a whole
circle, at the diameter.

00:13:40.826 --> 00:13:42.916 A:middle
If it's just an arc or part

00:13:42.916 --> 00:13:46.316 A:middle
of the circle, it
would be a radius.

00:13:46.316 --> 00:13:49.796 A:middle
You also need to add
the position dimensions

00:13:49.856 --> 00:13:53.986 A:middle
to locate all centerlines
of all circles as well

00:13:53.986 --> 00:13:55.216 A:middle
as other key features.

00:13:56.366 --> 00:13:57.446 A:middle
The size and position

00:13:57.446 --> 00:14:00.186 A:middle
of its feature must
only be defined once

00:14:00.756 --> 00:14:02.426 A:middle
to avoid over dimensioning.

00:14:02.866 --> 00:14:08.086 A:middle
So if you already indicated the
height of, say, the centerline

00:14:08.286 --> 00:14:10.126 A:middle
in the front of you, you
don't you don't need to do

00:14:10.126 --> 00:14:11.366 A:middle
that in the right side view.

00:14:11.526 --> 00:14:14.166 A:middle
Remember, the height
dimensions are--

00:14:14.596 --> 00:14:17.586 A:middle
can be shown both in the front
and in the right side view.

00:14:17.636 --> 00:14:20.156 A:middle
The depth can be shown
both in the south

00:14:20.156 --> 00:14:23.266 A:middle
and right side view while
the width can be shown

00:14:23.266 --> 00:14:26.216 A:middle
in the front or the top view.

00:14:26.306 --> 00:14:27.646 A:middle
You only need to show it once.

00:14:28.456 --> 00:14:32.876 A:middle
And as we said earlier,
you of dimensioning.

00:14:32.876 --> 00:14:36.716 A:middle
The view where it's-- showing
the most characteristic

00:14:36.716 --> 00:14:39.786 A:middle
or descriptive shape
of the object.

00:14:39.786 --> 00:14:44.426 A:middle
All English parts or dimensioned
into decimals and not fractions.

00:14:44.546 --> 00:14:50.056 A:middle
So architects like 1/16, 1834.

00:14:50.886 --> 00:14:52.176 A:middle
We use decimals.

00:14:53.006 --> 00:14:53.826 A:middle
Even for inches.

00:14:53.826 --> 00:14:58.326 A:middle
For metric parts, we use
millimeters also in decimals.

00:14:58.716 --> 00:15:01.766 A:middle
And we do not need to
indicate the units.

00:15:02.176 --> 00:15:04.936 A:middle
Because it will be very
apparent from the--

00:15:06.056 --> 00:15:11.126 A:middle
and understood from the drawing
itself whether it's in metric

00:15:11.326 --> 00:15:14.926 A:middle
or Imperial, whether it's
in millimeters or inches.

00:15:15.986 --> 00:15:21.356 A:middle
We always need to leave enough
spaces between the object

00:15:21.606 --> 00:15:23.266 A:middle
and the first row of dimensions.

00:15:23.266 --> 00:15:26.526 A:middle
You don't want the dimensions
to be too close to the object.

00:15:27.246 --> 00:15:29.336 A:middle
Successive rows of
dimensions should also have

00:15:29.786 --> 00:15:35.826 A:middle
at least .25 inch or six
millimeter spaces between them.

00:15:36.716 --> 00:15:41.156 A:middle
Very important place dimensions
outside of the views, okay,

00:15:41.156 --> 00:15:42.566 A:middle
because you don't
want to dimensions

00:15:42.746 --> 00:15:46.566 A:middle
in the dimension lines interfere
with the drawing itself.

00:15:46.566 --> 00:15:49.236 A:middle
Except for very,
very large circles.

00:15:49.236 --> 00:15:50.746 A:middle
If I have a very large circle,

00:15:50.746 --> 00:15:53.186 A:middle
I can put the dimensions
inside the circle.

00:15:53.756 --> 00:15:57.186 A:middle
One very important thing
here is illustrated here

00:15:57.186 --> 00:15:58.976 A:middle
for rule number 10.

00:15:59.486 --> 00:16:02.306 A:middle
You need to place
longer dimensions outside

00:16:02.306 --> 00:16:03.226 A:middle
of shorter ones.

00:16:03.226 --> 00:16:04.326 A:middle
Here's illustration here.

00:16:04.456 --> 00:16:09.316 A:middle
We're trying to-- notice the
dimensions 1.10 for the height

00:16:09.316 --> 00:16:14.776 A:middle
of the centerline here, and 1.70
for the height of this age here.

00:16:15.316 --> 00:16:16.926 A:middle
This is the correct way to do it

00:16:17.006 --> 00:16:21.846 A:middle
because the 1.70 is a longer
dimension compared to the 1.10

00:16:21.846 --> 00:16:24.046 A:middle
so you put 1.70 outside.

00:16:24.116 --> 00:16:26.986 A:middle
If you do it the
other way, like this,

00:16:27.496 --> 00:16:30.816 A:middle
the smaller dimension being
outside the longer dimension,

00:16:30.816 --> 00:16:34.006 A:middle
what happens is the
witness line here

00:16:34.006 --> 00:16:37.376 A:middle
for the 1.0 will cross
the dimension line.

00:16:37.496 --> 00:16:41.156 A:middle
You don't want witness lines
crossing dimension lines

00:16:41.156 --> 00:16:42.946 A:middle
or dimension lines
crossing each other.

00:16:43.906 --> 00:16:46.706 A:middle
Place the dimension text
between the dimension lines

00:16:46.706 --> 00:16:49.476 A:middle
so there should be a break
in the dimension lines

00:16:49.476 --> 00:16:50.816 A:middle
and the inserted
text in between.

00:16:51.726 --> 00:16:54.086 A:middle
Use the arrow heads
as shown here.

00:16:54.296 --> 00:16:56.476 A:middle
Same era size for
all the dimensions.

00:16:56.946 --> 00:16:58.126 A:middle
Inch drawings do not--

00:16:58.736 --> 00:16:59.756 A:middle
okay, here's one way

00:16:59.756 --> 00:17:02.226 A:middle
to distinguish whether
the dimensions are

00:17:02.486 --> 00:17:04.316 A:middle
in inches or millimeters.

00:17:04.756 --> 00:17:08.986 A:middle
Four inches, the preceding
zero is not included.

00:17:08.986 --> 00:17:13.906 A:middle
So for instance, for half of an
inch, one half inch, we use .50.

00:17:14.556 --> 00:17:17.786 A:middle
The fact that there's no zero
in front of the point we know;

00:17:17.946 --> 00:17:19.886 A:middle
we're implying that
it's in inches.

00:17:19.886 --> 00:17:21.846 A:middle
On the other hand,
for metric dimensions,

00:17:22.076 --> 00:17:24.206 A:middle
you include the preceding zero.

00:17:24.306 --> 00:17:30.676 A:middle
So one half of a
millimeter is shown as .0 .50

00:17:30.676 --> 00:17:32.326 A:middle
with a zero in front of it.

00:17:33.836 --> 00:17:37.036 A:middle
Okay before you submit your
lab on dimensioning's, okay,

00:17:37.346 --> 00:17:38.856 A:middle
what I want you to do is go

00:17:38.856 --> 00:17:41.396 A:middle
through the dimensioning
checklist to make sure

00:17:41.396 --> 00:17:44.406 A:middle
that you satisfy
all the requirements

00:17:44.446 --> 00:17:46.456 A:middle
and you are following
all the rules.

00:17:46.726 --> 00:17:49.216 A:middle
You're not violating any
of the dimensioning rules.

00:17:49.366 --> 00:17:53.166 A:middle
Number one overall dimensions
of the objects should be shown.

00:17:53.266 --> 00:17:56.936 A:middle
Front, the width, the
height, and the depth.

00:17:58.316 --> 00:18:00.576 A:middle
Dimensions are not
duplicated in two views.

00:18:00.576 --> 00:18:02.276 A:middle
If you are he showed
in the front,

00:18:02.316 --> 00:18:06.566 A:middle
for the height you're not show
it on the right side view.

00:18:07.416 --> 00:18:08.066 A:middle
And vice versa.

00:18:08.396 --> 00:18:10.176 A:middle
No dimension is included,
it's not needed

00:18:10.376 --> 00:18:13.276 A:middle
to produce the object. Remember that the
reason why you're putting the

00:18:13.276 --> 00:18:16.106 A:middle
dimensions is because
you're trying to make sure

00:18:16.106 --> 00:18:18.176 A:middle
that whoever looks at
your drawing will be able

00:18:18.176 --> 00:18:20.386 A:middle
to create whatever
parts you design.

00:18:21.096 --> 00:18:25.166 A:middle
So if a particular dimension is
not needed to proceed to produce

00:18:25.166 --> 00:18:28.416 A:middle
that object you don't
need included.

00:18:28.616 --> 00:18:31.916 A:middle
There's no need to calculate
scale or assume any dimension

00:18:31.916 --> 00:18:33.956 A:middle
to define or check features.

00:18:33.956 --> 00:18:38.316 A:middle
So it has to be completely
defined okay and also you want

00:18:38.436 --> 00:18:42.876 A:middle
to minimize errors on the part
of whoever's manufacturing it

00:18:42.916 --> 00:18:45.056 A:middle
by requiring them to
make calculations.

00:18:45.606 --> 00:18:48.276 A:middle
They don't need to
do any calculations

00:18:48.276 --> 00:18:50.636 A:middle
or make any assumptions
to create it.

00:18:51.226 --> 00:18:53.126 A:middle
The dimensions are
related to the view

00:18:53.406 --> 00:18:55.696 A:middle
that best describes
or shows the feature.

00:18:56.006 --> 00:18:57.256 A:middle
We are he talked about that.

00:18:58.226 --> 00:19:02.956 A:middle
Okay, whenever possible, you
try to place dimensions okay

00:19:03.026 --> 00:19:07.236 A:middle
in between the two views for
which they are applicable.

00:19:07.336 --> 00:19:10.596 A:middle
So height dimensions,
heights are shared

00:19:10.596 --> 00:19:13.356 A:middle
within the front
and the right views.

00:19:13.356 --> 00:19:16.876 A:middle
So you put it whenever
possible in between the front

00:19:16.876 --> 00:19:18.806 A:middle
and the right side views.

00:19:19.146 --> 00:19:22.306 A:middle
The other hand width
dimensions are shared

00:19:22.306 --> 00:19:24.026 A:middle
within the top and the front.

00:19:24.266 --> 00:19:27.576 A:middle
So whenever possible, put
width dimensions in between.

00:19:28.016 --> 00:19:31.266 A:middle
Multiple dimensions
should be uniformly spaced

00:19:31.266 --> 00:19:34.296 A:middle
and there should be a
minimum space in between them

00:19:34.296 --> 00:19:35.256 A:middle
in the final print out.

00:19:36.566 --> 00:19:39.536 A:middle
We Artie talked about this
longer dimensions are placed

00:19:39.536 --> 00:19:43.426 A:middle
outside shorter ones because
we don't want witness lines

00:19:43.506 --> 00:19:45.136 A:middle
crossing dimension lines.

00:19:46.496 --> 00:19:49.916 A:middle
All strings of dimensions are
lined up so if you have a series

00:19:49.916 --> 00:19:55.736 A:middle
of dimensions along a single
line they should be perfectly

00:19:55.736 --> 00:19:56.146 A:middle
lined up.

00:19:56.146 --> 00:19:59.516 A:middle
So one way to do that is
you can either you can rely

00:19:59.516 --> 00:20:01.816 A:middle
on your Osnaps or
maybe even your snap

00:20:02.236 --> 00:20:03.976 A:middle
when you're doing
it in AutoCAD.

00:20:04.046 --> 00:20:06.496 A:middle
Whenever possible when
dimensions are not given,

00:20:06.776 --> 00:20:10.846 A:middle
okay so this is kind of
emphasizing we said earlier.

00:20:11.376 --> 00:20:14.186 A:middle
You want to choose the view
where it's most descriptive.

00:20:14.566 --> 00:20:17.366 A:middle
And usually when it's a
hidden line it's not easy

00:20:17.416 --> 00:20:18.626 A:middle
to describe or visualize.

00:20:18.936 --> 00:20:22.956 A:middle
So whenever possible avoid
dimensioning hidden lines.

00:20:23.416 --> 00:20:26.346 A:middle
Of course, sometimes it's
not possible because may be

00:20:26.666 --> 00:20:29.816 A:middle
that feature only appears as
hidden in order to get the view.

00:20:30.676 --> 00:20:32.686 A:middle
Dimensions do not cross
other dimension lines

00:20:32.686 --> 00:20:33.426 A:middle
or witness lines.

00:20:33.856 --> 00:20:38.966 A:middle
Okay, again, so dimension lines
cannot cross each other witness

00:20:38.966 --> 00:20:41.246 A:middle
lines cannot cross
dimensions lines, however,

00:20:41.246 --> 00:20:42.936 A:middle
witness lines can
cross each other.

00:20:44.396 --> 00:20:49.426 A:middle
See this is a witness line
this is a witness line.

00:20:50.016 --> 00:20:52.326 A:middle
And they cross each
other perfectly fine.

00:20:52.916 --> 00:20:56.816 A:middle
Okay. Centerlines of all
arcs and circles are located

00:20:56.816 --> 00:20:59.156 A:middle
with respect to the important
features of the object.

00:20:59.156 --> 00:21:01.856 A:middle
So when you ever you
have a circle or any arc,

00:21:02.986 --> 00:21:04.806 A:middle
you need to make
sure that number one,

00:21:04.806 --> 00:21:08.756 A:middle
the centerline symbols are
indicated in the drawing.

00:21:08.756 --> 00:21:10.956 A:middle
Number two, that the locations

00:21:10.956 --> 00:21:14.286 A:middle
of the centerlines are
indicated by dimensions.

00:21:15.416 --> 00:21:18.656 A:middle
The radius of all arcs
and fillets and diameters

00:21:18.656 --> 00:21:20.766 A:middle
of all circles have
been specified.

00:21:20.766 --> 00:21:22.726 A:middle
Again, if it's a whole circle,

00:21:23.506 --> 00:21:26.196 A:middle
you use the diameter
symbol indicate the diameter

00:21:26.196 --> 00:21:26.686 A:middle
of the circle.

00:21:26.966 --> 00:21:30.156 A:middle
It's only part of a
circle, such as an arc,

00:21:30.906 --> 00:21:33.226 A:middle
or a fillet, use radius.

00:21:33.696 --> 00:21:35.776 A:middle
A little bit more
about tolerances.

00:21:36.656 --> 00:21:41.576 A:middle
Two different ways of indicating
tolerance again tolerance means

00:21:41.576 --> 00:21:43.786 A:middle
that were allowing that
particular dimension

00:21:43.856 --> 00:21:48.346 A:middle
to deviate slightly
from the ideal value.

00:21:49.196 --> 00:21:52.216 A:middle
So in the limit tolerance
you indicate the highest

00:21:52.216 --> 00:21:54.406 A:middle
and the lowest possible
limits of the object.

00:21:55.016 --> 00:21:59.886 A:middle
Example, you indicate
12.0 to 12.5 saying

00:21:59.886 --> 00:22:03.766 A:middle
that that dimension is
acceptable as long as it's

00:22:03.766 --> 00:22:06.806 A:middle
at least 2.0 and at most 12.5.

00:22:07.166 --> 00:22:08.886 A:middle
On the other hand, the plus

00:22:08.886 --> 00:22:16.396 A:middle
and plus minus tolerance gives
a targets or nominal value okay

00:22:16.396 --> 00:22:21.526 A:middle
and then you get a plus
error and then a minus error.

00:22:22.106 --> 00:22:23.256 A:middle
Plus or minus okay.

00:22:23.256 --> 00:22:28.416 A:middle
That's followed by a plus
minus expression of tolerance.

00:22:28.526 --> 00:22:33.906 A:middle
So example is 12.5
plus or minus .25.

00:22:34.286 --> 00:22:38.256 A:middle
So this plus minus severance
expression is equivalent

00:22:38.256 --> 00:22:38.816 A:middle
to this.

00:22:39.306 --> 00:22:43.056 A:middle
Okay were saying that
here the target is 12.25.

00:22:43.476 --> 00:22:49.206 A:middle
It could be smaller by up
to -.25 or bigger by up

00:22:49.276 --> 00:22:52.366 A:middle
to .25 giving exact
limit tolerance.

00:22:52.366 --> 00:22:54.406 A:middle
This is an example of
plus minus tolerance

00:22:54.456 --> 00:22:56.616 A:middle
but it's bilateral and equal.

00:22:57.726 --> 00:23:01.816 A:middle
So here's some illustrations
in terms

00:23:01.816 --> 00:23:04.186 A:middle
of representing tolerance
values.

00:23:04.186 --> 00:23:07.516 A:middle
So this is limits
minimum here in maximum

00:23:08.536 --> 00:23:10.976 A:middle
and here's plus minus.

00:23:12.126 --> 00:23:13.966 A:middle
Here's the target
value, nominal value,

00:23:13.966 --> 00:23:16.036 A:middle
and the plus minus,
and this is the error.

00:23:16.706 --> 00:23:19.356 A:middle
Now, for the plus minus,
you have something called

00:23:19.446 --> 00:23:23.076 A:middle
by lateral tolerance which
means that you are allowed

00:23:23.706 --> 00:23:27.856 A:middle
or you can have an error both in
the plus or the minus direction.

00:23:27.946 --> 00:23:34.786 A:middle
If they are equal, meeting the
error in the positive is as big

00:23:35.266 --> 00:23:38.366 A:middle
or can be as big as the
error in the negative,

00:23:38.366 --> 00:23:39.786 A:middle
it's called equal bilateral.

00:23:40.656 --> 00:23:45.326 A:middle
On the other hand, it's an
equal bilateral if the variation

00:23:45.326 --> 00:23:48.396 A:middle
in the positive is not the
same as the variation--

00:23:48.396 --> 00:23:50.196 A:middle
allowable variation
in the negative.

00:23:51.106 --> 00:23:53.196 A:middle
Okay sometimes you for plus

00:23:53.196 --> 00:23:57.056 A:middle
or minus tolerance you can only
have a unilateral tolerance.

00:23:57.056 --> 00:23:59.416 A:middle
Meeting you only
allow it to be--

00:23:59.596 --> 00:24:02.836 A:middle
to vary, or be an
error in one direction.

00:24:03.626 --> 00:24:05.566 A:middle
And no error in the
other direction.

00:24:05.566 --> 00:24:10.896 A:middle
So for example if you look
at a bolt and a nut, okay,

00:24:10.896 --> 00:24:12.396 A:middle
you want to make
sure that the nut,

00:24:12.926 --> 00:24:15.746 A:middle
the bolt will go inside
the nut which means

00:24:15.846 --> 00:24:19.826 A:middle
that the bolt can be slightly
smaller but not bigger

00:24:20.016 --> 00:24:22.576 A:middle
because otherwise it will
not go into the bolt.

00:24:22.946 --> 00:24:26.936 A:middle
On the other hand, the
knot can be slightly bigger

00:24:27.366 --> 00:24:31.096 A:middle
but not smaller than the target
area otherwise it will not be

00:24:31.186 --> 00:24:33.246 A:middle
big enough to accommodate
the diameter.