1. ## Tan Tan Radius question

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Hi,

I'd like to draw the image below in 2D but I hit a problem with the bottom part in relation to the side radius of 3.5mm.

Drawn the circle with a radius of .75 so I can use the "Circle>Tan Tan Radius" command to make the radius 4.25mm. Trimmed the excess edges and used PEDIT so I can apply offset .75mm outwards. The offset polyline showed some error that did not gel well with the bottom portioon. (the error is encircled in red). Edges would not meet as in the drawing exercise.

Now redone it using the Tan Tan Radius based on the bigger diameter but the result is the same as that of the .75 offset polyline result.

Now if I tried to drag the endpoints to meet the end of the 1.5mm x 4mm base but the radius will change. It says there that the radius will change to 4.008mm. Drawing exercise says it should be radius of 3.5mm.

Same with the bottom portion. If I drag the bottom part to meet the excess of the circle/arc created via the tan tan radius, 1.5mm x the 4mm dim will be affected. See image attached.

The other dims are correct but this radiius of 3.5mm is not. There could be something wrong with the way I did the circle with the Tan Tan Radius....

How will you do the drawing if it were you....?

Can you teach a self-studier some tips and tricks please...

Thank you!

2. Can you attach an image or the drawing
its hard to follow what you are trying to do without a picture

3. In my opinion the dimensions are all correct. It is your approach that is in error. Draw the perimeter first then offset to the inside. Trim as required. Like this...

DwgExercise.PNG

4. Originally Posted by MinaRAI
Drawn the circle with a radius of .75 ....
This dimension is not on your drawing...
Work from the outside towards the inside as ReMark suggested.

1. You know that the center of the arc is somewhere in space 3.5 from the endpoint of the 1.5 vertical line.
2. You know that the center of the arc is somewhere in space 5 (1.5+3.5) from the center of the smaller circle.

There are only two points in space that satisfy both of those conditions.
One of the two possible solutions does not make logical sense.
You have found the unique solution. (the construction lines in the image below are not needed - I included them only for illustration)
Solution.png

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Oh wow! Thank you for the set of instructions there. I really went from slow to very slow understanding or trying to remember drafting 101...I had the chance to do it in a different version. Please see below.

Someone mentioned also that this can be done via a point_tan_radius..

Can you guys help me understand that too...

I really appreciate the guide drawings. Thanks very much for that. Please bear with me as I am currently having trouble with where to go for self-study at the moment as the previous location I did went is having problems. Had to do the drawing based on the illustrations and a couple help from other concerned gurus on a different version(2013). And it took me hours for just this one...(no kidding on it. I think I went blank trying to grasp the newer version from 2010 from which I also am trying to use. Had just started late June till now intermittently.)

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