Drafting Techniques

Drafting Techniques

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Distinguished Contributor kb
Distinguished Contributor
kb
Posts: 201
Registered: ‎11-25-2003
Message 1 of 54 (353 Views)

Dimensioning an isometric drawing

353 Views, 53 Replies
09-01-2003 10:06 AM
How can I dimension an isometric drawing? When I try to dimension an object, the dimension lines do not follow the object correctly. They dimension in a 2d view. It doesn't matter if I switch on the drafting setting to use isometric views. Or even change the to the top, left or right. It still dimensions strangely.

Is there another setting I'm missing? Please let me know. I'm using ACAD 2004.
*jonesr
Message 2 of 54 (353 Views)

Re: Dimensioning an isometric drawing

09-01-2003 11:18 AM in reply to: kb
DIMALIGNED?


style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
How
can I dimension an isometric drawing? When I try to dimension an object, the
dimension lines do not follow the object correctly. They dimension in a 2d
view. It doesn't matter if I switch on the drafting setting to use isometric
views. Or even change the to the top, left or right. It still dimensions
strangely.

Is there another setting I'm missing? Please let me know. I'm using ACAD
2004.

*Larsen, Henny
Message 3 of 54 (353 Views)

Re: Dimensioning an isometric drawing

09-01-2003 07:44 PM in reply to: kb
dimedit > select Oblique > select object >
enter angle to set extension lines for dimension.


style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
How
can I dimension an isometric drawing? When I try to dimension an object, the
dimension lines do not follow the object correctly. They dimension in a 2d
view. It doesn't matter if I switch on the drafting setting to use isometric
views. Or even change the to the top, left or right. It still dimensions
strangely.

Is there another setting I'm missing? Please let me know. I'm using ACAD
2004.

*Richardson, Randy
Message 4 of 54 (353 Views)

Re: Dimensioning an isometric drawing

09-01-2003 10:58 PM in reply to: kb
I have noticed that some people have a
misunderstanding of what an isometric drawing is.  Some people think that
an isometric view is an accurate view of an object, viewed from a certain skewed
angle.  If that is your understanding of an isometric drawing, then
attempting to dimension it using isometric options views will not work. 
Could that be the problem?


style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
How
can I dimension an isometric drawing? When I try to dimension an object, the
dimension lines do not follow the object correctly. They dimension in a 2d
view. It doesn't matter if I switch on the drafting setting to use isometric
views. Or even change the to the top, left or right. It still dimensions
strangely.

Is there another setting I'm missing? Please let me know. I'm using ACAD
2004.

*Richardson, Randy
Message 5 of 54 (353 Views)

Re:

09-01-2003 11:11 PM in reply to: kb
I'll expand on what I wrote for the benefit of
anyone who is unclear as to what I'm saying.  Isometric drawing is a 2D
method of drawing an object in such a way that a viewer of the drawing gets a
rough idea what the shape of the object is.  It was never meant to be an
accurate depiction, only an approximation.  The methods used to draw the
line lengths are meant for ease of use for a drafter using drafting tools,
rather than for creating an accurate picture.  Perhaps in the age of 3D
drafting it is no longer necessary to use the conventions of isometric
drawing.

 

Perhaps it would be helpful to compare it to the
various methods used to represent a map of the whole planet on a flat
sheet.  There is no way to accurately depict the entire planet on a flat
sheet without showing distortions.  The difference from one method to
another is deciding which features to distort.  The world-famous Merceator
(sp?) Projection shows the north pole as being the same length as the
equator.  We know that that is a distortion, but it is true to the rules
set forth to create a Merceator Projection.  In like manner, an isometric
drawing uses various agreed-upon rules to make a somewhat distorted image. 
It is based more on ease of drawing than absolute accuracy.

 

Computers perhaps render such concerns moot, but I
still have vivid memories of drawing everything by hand.  When AutoCAD was
created, they obviously wanted to mimic most of the conventions that draftsmen
have always used, whether they made sense for computers or not.  I only
wish they had paid more attention to how hidden lines should be represented in
various situations.  That is still done incorrectly, to this day, but now
it's become so common due to CAD ubiquity that what was once frowned upon is now
accepted.

 

-Randy Richardson


style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">

I have noticed that some people have a
misunderstanding of what an isometric drawing is.  Some people think that
an isometric view is an accurate view of an object, viewed from a certain
skewed angle.  If that is your understanding of an isometric drawing,
then attempting to dimension it using isometric options views will not
work.  Could that be the problem?


style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
How
can I dimension an isometric drawing? When I try to dimension an object, the
dimension lines do not follow the object correctly. They dimension in a 2d
view. It doesn't matter if I switch on the drafting setting to use isometric
views. Or even change the to the top, left or right. It still dimensions
strangely.

Is there another setting I'm missing? Please let me know. I'm using ACAD
2004.

Distinguished Contributor
old-cadaver
Posts: 5,183
Registered: ‎12-12-2003
Message 6 of 54 (353 Views)

Re:

09-01-2003 11:35 PM in reply to: kb
>>I only wish they had paid more attention to how hidden lines should be represented in various situations. That is still done incorrectly, to this day,<<

?? Isn't that the drafter's responsibility??
*Richardson, Randy
Message 7 of 54 (353 Views)

Re:

09-01-2003 11:47 PM in reply to: kb
You're right.  The entire drawing is the
drafter's responsibility.  To their credit, Autodesk has made it easy for
drafters to fulfill their responsibility correctly in most respects, so perhaps
I should not complain about one of the few areas where they have utterly failed
to do so.  I think that very few drafters in this day and age are aware
that it's not always desirable to start a hidden line with a segment instead of
a gap.  Perhaps this can be blamed on the fact that we there are fewer
drafting classes and more CAD classes these days.  To me it is frustrating,
and I'm powerless to affect things much.  Fortunately, I don't lose any
sleep over this.


style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">

>I only wish they had paid more attention to how hidden
lines should be represented in various situations. That is still done
incorrectly, to this day,<<

?? Isn't that the drafter's responsibility??

Distinguished Contributor
lsaapedd
Posts: 587
Registered: ‎12-10-2003
Message 8 of 54 (353 Views)

Re:

09-02-2003 02:58 AM in reply to: kb
>I think that very few drafters in this day and age are >aware that it's not always desirable to start a hidden >line with a segment instead of a gap.

Explain please. I can not remember EVER starting a hidden line with a gap, and the classes I took did not mention any reason to do so.

Jerry
*Richardson, Randy
Message 9 of 54 (353 Views)

Re:

09-02-2003 03:30 AM in reply to: kb
If an object line ends at the same point as a
hidden line, and if they depart from that same point in opposite directions, the
intent is clearer and it looks cleaner if the hidden line starts with a
gap.  This is how I was trained when I used a pencil instead of a
mouse.  Since AutoCAD cannot have a hidden line that starts with a gap, I
compensate by breaking the hidden line a little distance from the
end.  If your classes were CAD classes rather than drafting classes, I'm
not surprised that they never mentioned this.  If they were drafting
classes, then they should have (IMHO) mentioned it.

 

-Randy


style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">

I think that very few drafters in this day and age are
>aware that it's not always desirable to start a hidden >line with a
segment instead of a gap.

Explain please. I can not remember EVER starting a hidden line with a gap,
and the classes I took did not mention any reason to do
so.

Jerry

*jonesr
Message 10 of 54 (353 Views)

Re:

09-02-2003 03:41 AM in reply to: kb
Amen on the "CAD Operator" class vs. Drafting. CAD
training  is long on commands on short on technique.


style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">

If an object line ends at the same point as a
hidden line, and if they depart from that same point in opposite directions,
the intent is clearer and it looks cleaner if the hidden line starts with a
gap.  This is how I was trained when I used a pencil instead of a
mouse.  Since AutoCAD cannot have a hidden line that starts with a gap, I
compensate by breaking the hidden line a little distance from the
end.  If your classes were CAD classes rather than drafting classes, I'm
not surprised that they never mentioned this.  If they were drafting
classes, then they should have (IMHO) mentioned it.

 

-Randy


style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">

I think that very few drafters in this day and age are
>aware that it's not always desirable to start a hidden >line with a
segment instead of a gap.

Explain please. I can not remember EVER starting a hidden line with a
gap, and the classes I took did not mention any reason to do
so.

Jerry

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