Make Circle go through point with a certain distance from other point

[jacob]

Just to learn more about AutoCAD, since I switched CAD software.

See on the attached image.

How can a make this circle go through a point with a certain distance (blue) from the polygon corner (red)?

How do i practically do that.

I tried the "From" command etc. however everything i tried puts the setted distance from the center fo the circle/polygon ...

Advices appreciated 😉

Cheers, Jacob

[pendean]

Your hexagon's points (if a true hexagon) will fit in a circle: since you have the center poinf of the hexagon drawn, you know the distance to any one of those points. Now just add the blus distance to it.

Example: CIRCLE command, RADIUS option, click in the center point to start the dim then enter the total final distace OR click on one of the points of the Hexagon to finish the circle then use OFFSET command for the blue distance.

[jacob]

sure, however, thats not a sober CAD solution 🙂

[JDMather]

Offset isn't "sober"?

What CAD program did you switch from?

For rock solid CAD, you might want to look at the Parameters tab.

[pendean]

LOL, sometimes high school geometry is all you need, cad is overkill 😉

[jacob]

Coming from Nemetschek Allplan, verry beautiful programm, however not for
micrometer scale drawing, which is what I need atm.

Topic: There must be a way to accomplish that with a handy worlflow.

[JDMather]

---

@jacob wrote:
Topic: There must be a way to accomplish that with a handy worlflow.

---

There is - it is a trivially simple geometry problem.

[jacob]

Yeah, but how can I accomplish it without calculating the total radius.

How can this be done in AutoCAD just with your mouse?

Thanks,

Jacob

[JDMather]

I teach my students how to use geometry without any calculations.
Typically, I will have them start out with simple numbers (dimensions) and then work backwards to general solutions that involve only the geometry and don't require knowing any of the dimensions.  Once they understand general geometric solution, then they can enter known parameters and the CAD program figures out the unknown parameters.

Can you sign up for a class?

What are you trying to design?

Do you have a specific problem that someone can walk you through step-by-step?

You might look into geometric constraints and parametric dimensions.  (this functionality is a little bit harder to use in AutoCAD than in other CAD programs, but might serve as a good introduction to geometry)

[jacob]

Thats my point, I dont wanna calculate any dimensions. I want do solve the described issue by using nice CAD techniques, step by step, in a convenient workflow.

So does anyone know how to draw this circle?

Maybe an way to solve it:

How can I offset a temporary point along a line?

[sthompson1021]

OK, stupid question time. Do you know how to use grips and snaps because if you don't the attached dwg won't do you any good.

Here's 2 ways to do it without any math involved.

[sthompson1021]

sorry forgot the dwg

[JDMather]

---

@jacob wrote:

Thats my point, I dont wanna calculate any dimensions.  

---

You are trying to skip a step in the learning process I use as described previously,

"Typically, I will have them start out with simple numbers (dimensions) and then work backwards to general solutions that involve only the geometry and don't require knowing any of the dimensions.  Once they understand general geometric solution, then they can enter known parameters and the CAD program figures out the unknown parameters."

I know your end goal is to do without calculations, but first give me something verifiable that I know we are communicating on the same page - then I can go to general geometric solutions.

[jacob]

Dear sthompson1021,

thank you for the instructions. The first solution is way more sober than I did ...

I did the second way by drawing a perpendicular with a certain distance.

However both are not perfect as you have to draw additional object (a second circle or the perpendicular)

Isn't it possible to do that on the first and only circle you draw?

Something like: Draw circle -> define center -> define the point where it should go through -> set this point distance x from the hexagon point in line direction - FINISH

???

Cheers,

Jacob

[sthompson1021]

I don't know of any OOTB command to do what your asking. It may be possible with a LISP routine or possibly with parametric constraints. I don't use them so I not sure.  

[doni49]

---

@sthompson1021 wrote:

I don't know of any OOTB command to do what your asking. It may be possible with a LISP routine or possibly with parametric constraints. I don't use them so I not sure.  

---

Yes it's possible.  But I wouldn't want to type it everytime (assuming you're doing it often -- if you are then I'd suggest saving it in a lisp file).

When prompted for your radius enter the following (make sure to include the parenthesis).

(+ (getdist (getpoint "Pick center point:  ") "Pick point from which to offset:  ") 2)

This will prompt you for the center point, then the point from which to offset (the corner of the polygon in this case), then draw your circle 2 units larger than the distance you selected.

If you are going to do this often, then save the follwing to a file with an extension of lsp (for example:  radplus2.lsp).  (and do a google search for instructions on loading and using a lsp file -- search terms:  "Autocad load autolisp file".  Once you've loaded the file into acad, you'll type 'radplus2 when prompted for the radius.

(defun c:radplus2()

 (+ (getdist (getpoint "Pick center point:  ") "Pick point from which to offset:  ") 2)

)

[sthompson1021]

Can't figure out why it keeps coming up that I'm replying to myself. Anyway, I figured someone would come thru with a lisp. If you replaced the 2 with a blank space at the end of the lisp, could you enter a offset distance when running the command instead of having it set at 2?

[doni49]

---

@sthompson1021 wrote:

Can't figure out why it keeps coming up that I'm replying to myself.

---

Two possibilities:

1. Did you click Reply and then have to deal with the login prompt and then after that enter your message?  If so, that's just the way this site works.  If you want to reply and have it correctly ID as "reply XXXXX", click sign and THEN do your reply.
2. Are you sure you didn't click "Reply" at the bottom of your message?  That would certainly do it.

---

@sthompson1021 wrote:

Anyway, I figured someone would come thru with a lisp. If you replaced the 2 with a blank space at the end of the lisp, could you enter a offset distance when running the command instead of having it set at 2?

---

 No -- the routine as written expects to add two numbers:  a number returned by the "Getdist" function and the number 2.  If you want to allow for entering the desired offset distance at runtime, you could replace the 2 by the following (getreal "Enter the offset distance:  ").

[sthompson1021]

It was the login that did it. Just curious about the LISP.

To me it stills seems easier to to just offset the circle.

[doni49]

---

@sthompson1021 wrote:

It was the login that did it. Just curious about the LISP.

To me it stills seems easier to to just offset the circle.

---

I would definitely agree with that.  UNLESS there are a bunch of them to do -- in such a case, I might very well use a lisp routine.