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# How to Draw Arc in the Draftsman Method?

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dery
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Post Options    Thanks(0)    Quote  Reply Topic: How to Draw Arc in the Draftsman Method?
Posted: 13.Apr.2018 at 18:02
How to draw an arc that tangent to both green line and blue line (please see below image for detail) in draftsman way?

'I know that in AutoCAD we can use the Ttr or Arc command.

Kent Cooper
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Post Options    Thanks(0)    Quote  Reply Posted: 13.Apr.2018 at 18:56
If you're talking about doing it on paper, the Arc approach in AutoCAD can probably be duplicated on paper more easily than the Circle/TTR approach [unless you have a circle template with a circle hole of the right radius].  It would be to OFFSET both Lines by the Radius distance, toward the center, then ARC command, Center option at the Object-snapped INTersection of the resulting Lines, start point Osnapped PERpendicular from there to the right-edge original Line, end point PERpendicular to the other.  [It could also be done by FILLETing the Lines to the desired radius, then again to zero radius, but that can't be duplicated in paper drafting.]

To do it on paper, you would duplicate the above process -- draw lines parallel to the originals by measuring the radius distance off them perpendicular to each at two locations to get the parallel lines, put the compass point at their intersection, set the drawing point to meet one line, and sweep the arc.

Edited by Kent Cooper - 13.Apr.2018 at 19:05
dery
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Post Options    Thanks(0)    Quote  Reply Posted: 16.Apr.2018 at 12:37
 Kent Cooper wrote: If you're talking about doing it on paper, the Arc approach in AutoCAD can probably be duplicated on paper more easily than the Circle/TTR approach [unless you have a circle template with a circle hole of the right radius].  It would be to OFFSET both Lines by the Radius distance, toward the center, then ARC command, Center option at the Object-snapped INTersection of the resulting Lines, start point Osnapped PERpendicular from there to the right-edge original Line, end point PERpendicular to the other.  [It could also be done by FILLETing the Lines to the desired radius, then again to zero radius, but that can't be duplicated in paper drafting.] To do it on paper, you would duplicate the above process -- draw lines parallel to the originals by measuring the radius distance off them perpendicular to each at two locations to get the parallel lines, put the compass point at their intersection, set the drawing point to meet one line, and sweep the arc.

Could you please explain it by using image/picture?
philippe JOSEPH
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Post Options    Thanks(0)    Quote  Reply Posted: 16.Apr.2018 at 13:10
Hello dery and kent, see the file : DRAW ARC DRAFSMAN METHOD.dwg in the CAD/BIM Blocks library here in the site.
Dery, please try and search a little...
AutoCAD is nothing else than an electronic drawing board ( it can be much more ) but if you don't know how to draw it won't do the job just for you.

Edited by philippe JOSEPH - 16.Apr.2018 at 13:15
Philippe JOSEPH
dery
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Post Options    Thanks(0)    Quote  Reply Posted: 16.Apr.2018 at 14:32
 philippe JOSEPH wrote: Hello dery and kent, see the file : DRAW ARC DRAFSMAN METHOD.dwg in the CAD/BIM Blocks library here in the site.Dery, please try and search a little...AutoCAD is nothing else than an electronic drawing board ( it can be much more ) but if you don't know how to draw it won't do the job just for you.

Could you please show me the link? I already searched for the one you mentioned above but still can't find it.
John Connor
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Post Options    Thanks(0)    Quote  Reply Posted: 16.Apr.2018 at 15:25
Put your glasses on.  This website (i.e. - The CADforum)....CAD/BIM Blocks.  The drawing is the very first one at the top of the list.  Doesn't get any easier than that.
"Humans have a strength that cannot be measured. This is John Connor. If you are reading this, you are the resistance."

Kent Cooper
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Post Options    Thanks(0)    Quote  Reply Posted: 16.Apr.2018 at 16:03
dery wrote:

 Kent Cooper wrote:.... draw lines parallel to the originals by measuring the radius distance off them perpendicular to each at two locations to get the parallel lines....
Could you please explain it by using image/picture?

I assume the challenge is to make the equivalent of OFFSET on paper, ensuring that the result is parallel to the original.  If you have had a class in plane geometry using straight-edge and compass techniques, you should have learned how to establish a line perpendicular to another line.  One way:
Yellow is the original Line.  Swing two arcs [of any radius -- they can even be different radii] with their centers on that Line [cyan and magenta], and the line between their intersections [red] will be perpendicular to the yellow Line.  Do that at two locations, and measure the Radius distance from the yellow Line along the red ones at each location, to establish points through which to draw the offset line.  Do that from both original Lines, and the intersection of those offset lines will be the center of the new Arc.

[By the way, in AutoCAD commands, in addition to Arc and Circle-TTR mentioned before, there's also FILLET with the Trim option set to No-Trim.  That's the fastest way, since it does not require Offsetting to find the center as the Arc method does, nor Trimming as the Circle-TTR method does.]
philippe JOSEPH
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Post Options    Thanks(0)    Quote  Reply Posted: 16.Apr.2018 at 18:46
Hello dery, the CAD/BIM Blocks library is here and you need 2 clics to reach the AutoCAD file.
Philippe JOSEPH
Gsourcetechnologies
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Post Options    Thanks(0)    Quote  Reply Posted: 20.Apr.2018 at 14:15
Hi Dery,
It is a very simple process, follow these steps,

1. Draw the triangle by using poly line command with the help of given dimensions.
2. Go to circle option from there select tan,tan,tan option
3. select the three sides of triangle that you have drawn
4. trim the unwanted circle part by keeping arc tangent to to the sides of triangle.

Gsource Technologies, https://www.gsourcedata.com/
Gsourcetechnologies
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Post Options    Thanks(0)    Quote  Reply Posted: 20.Apr.2018 at 14:19
There are other options too, if you know the radiun of arc, then use tan,tan,radius option. hope this solves your problem, keep me posted.
Gsource Technologies, https://www.gsourcedata.com/