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What is the easiest way to draw center line for a circle?


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Sengna

I was wondering if there is any easier way to draw center line for a circle, i usually draw 2 construction lines perpendicular to each other and trim or draw a outer reference circle and extend the line as this image below. the yellow lines showed as continue I have to set LTS so the center line show properly. thanks.

 

 

center line.png

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Dana W

You seem to be getting the idea. You did figure out how to use the center line type. You are putting all your center lines on their own layer, with the line type and line properties controlled by layer, right?

 

Here is an easy way.to draw exactly equal length perp CL's.

 

You will want Ortho OFF, Object snaps ON, especially center, Auto Track, and Polar Tracking ON(drafting settings). You ALWAYS are going to want tracking vectors on. (Options, Drafting tab) Full screen tracking vectors are up to you. Most of this stuff should already be set right, with the exception of ortho and polar tracking, both of which you can toggle at will. None of the above set up needs to be part of the center line drawing exercise if it is ready to go before.

 

Draw one center line the length you like. It does not matter which one of the two you draw first. Make sure the midpoint of the center line is snapped to the center snap of your circle. The offset temp circle you made is a good guide, or simply draw a center line someplace and move it by the midpoint to the circle center snap.

 

Now mirror that line across a 45 deg tracking vector passing through the center of the circle rather than using an actual line for a mirror plane. Bang, done.

 

Here's how to mirror that way. Start the mirror command. Select the first center line as your object to mirror. "draw" the mirror line by selecting the center snap of your circle as the first point of the mirror line. Now for the other point of your mirror line move the cursor out from the center point of your circle for a bit at an approximate 45 deg angle, into some empty modelspace. It doesn't matter which of the 4 possible directions you move. What you want to see is a tracking vector (feint dashed line) to develop between your cursor and the other end of the mirror line at the center of the circle. You will see that angles are displayed, and that the tracking vector seems to LOCK on to certain angles.

 

When you see the vector LOCK onto 45 deg or any of the reciprocals of 45 deg. You can click the second point of your mirror line, and you are done. You now have exactly equal, and symmetrical center lines for your hole. It takes a lot of words to describe how to do this, but very little time and effort. Once you get used to utilizing tracking vectors, you can mirror most anything across any nonexistant line at any angle. In Drafting Settings, Polar Tracking tab, you will see that your tracking angle increment defaults to 15 deg. Your tracking vector will LOCK onto each of those angles. The angle increment can be changed, and you can add additional increments. You can have tracking increments of every 4 deg and every 15 deg at the same time if you want. The polar tracking angle can be set to relative to the last segment or absolute, which is relative to the modelspace X axis.

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Dadgad

The hands down easiest way to draw a centerline for a circle, or even for say 2000 different sized circles

all at once in under a second, with custom fitted lengths is http://www.lee-mac.com/associativecenterlines.html .

If you aren't using it, you are wasting a lot of time.

This is in my startup lisp folder, and it sees a lot of use.

When you open the lisp you will see where you can define how long the lines should be

relative to the diameter of the circles.

 

Just remember to set the appropriate layer current before running it.

 

Brilliant, of course we would expect no less from Lee Mac!

I choose to use NONASSOCIATIVE centerlines, so after running it on my circles,

defined with a crossing window, I then invoke CLR (for centerline REMOVE associativity) at the commandline,

and accept the default , just hit ENTER, without making any additional selection.

 

Lee also has another one for drawing non-orthogonal centerlines, can also handle ellipses, equally brilliant,

but I have much less call for that in my detailing work.

 

http://www.lee-mac.com/centreline.html

 

Done deal. Thanks Lee! :beer:

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Sengna

[quote name=Dana W

Now mirror that line across a 45 deg tracking vector passing through the center of the circle rather than using an actual line for a mirror plane. Bang, done.[/b].

Little confuse Dana, why use 45 deg tracking vector for mirror line not 90 deg?

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Dadgad

Dana is fast asleep by now. :|

When you use the 45 degree tracking vector as your MIRROR LINE, and crossing the center of your circle, the new line will be at 90 degrees relative to the original line.

Try it, and you will understand it.

 

Another easy analog solution is to make a custom Tool Palette which includes a good library of hole centers.

 

But Lee's lisp is the way to go if you want to save some serious time and effort.

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Dana W
Little confuse Dana, why use 45 deg tracking vector for mirror line not 90 deg?
Yes, I was asleep.

Because mirroring at 45 deg. makes a reflection 90 deg off the original. It's geomonometry, not rocket sergoery.:P:;):lol:

 

Light bounces away in the opposite direction (mirroring) at exactly the incoming angle of intersection with a surface. 45 + 45 = 90.

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Dana W

You could also build a dynamic block which stretches both center lines the same distance at the same time.

 

Another way is to have a dim style with one extension line being a center line.

 

All of the above can mix depending on circumstances.

 

Personally, I think all of the suggestions in this thread are like killing a fly with a shotgun. I just eyeball the center lines in and move on. Then again, I do architectural drawings, and they should look like a human did 'um.

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Sengna

[quote name=

If you aren't using it' date=' you are wasting a lot of time.

 

When you open the lisp you will see where you can define how long the lines should be

relative to the diameter of the circles.

 

Just remember to set the appropriate layer current before running it.[/quote] Thank Dadgad! I have already downloaded from Lee Mac and i am reading the instruction of how to install this lisp right now, will let you know it this will work..

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Sengna

If you aren't using it, you are wasting a lot of time.

This is in my startup lisp folder, and it sees a lot of use.Just remember to set the appropriate layer current before running it.:beer:

 

Thank Dadgad! I have already downloaded from Lee Mac and i am reading the instruction of how to install this lisp right now, will let you know it this will work..

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Dadgad
Thank Dadgad! I have already downloaded from Lee Mac and i am reading the instruction of how to install this lisp right now, will let you know it this will work..

 

Glad to hear it, you will be glad you did. :)

Maybe it is overkill if you are just drawing one, but in my drawings I might have 100 or more on a steel detail sheet,

and they might be half a dozen different sizes. I define my centerline length as 1.5 times the diameter, whatever you like.

As soon as you invoke the command, and window your selection area, no need to choose the circles, just define the window

where they are to be found, ENTER, bingo they are all done, and the centers are spot on. Very efficient.

 

Thanks Lee! :beer:

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Sengna

It looks like i got the lisp file install succesfully. now i opened up Autocad, i have 3 circles on the screen and what is the lisp command prompt to use for center line?

centerline.jpg

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Dadgad

You call the lisp at the commandline with CL.

Remember to switch to the layer upon which you want the centerlines to be created

before running it.

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Sengna
You call the lisp at the command line with CL.

Remember to switch to the layer upon which you want the center lines to be created

before running it.

I switched to one layer called " Center line", i typed CL--select objs then i selected multiple circles then entered, i can see the center line was placed automatically one by one, How come the center line didn't show as center, they look like contentious lines, do i fix that by LTS or am i missing some steps?

Work great so far I can see a light at the end of the tunnel Lol.

Layers.jpg

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Dadgad

The lisp will create lines indicating the middle of the holes, on whichever layer is current, and the linetype used for them will be the linetype which

is assigned to that layer. I should think that the Line Type of a layer named Center line would most likely be CENTERLINE.

If you open your layer properties manager you can check the layer definition, and if you need to, you can change the linetype of that layer to centerline

in the layer properties manager.

 

The length of the lines created is defined by the ratio you set in the lisp, based on the diameter of the circle.

 

Please look at the snippet I took of Lee's code, on Line 13.

This is where you can set the ratio of line length to circle diameter.

If you open Lee's lisp with NOTEPAD, you can edit it, and change the red circled value to whatever

ratio you think is the best, Lee's default length is 1.25.

Then save and close Notepad.

 

Thanks to Lee Mac for this awesome tool! :beer:

this is where you set the ratio in Lee Mac's associative centerline lisp.JPG

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Sengna
The lisp will create lines indicating the middle of the holes, on whichever layer is current, and the linetype used for them will be the linetype which

is assigned to that layer. I should think that the Line Type of a layer named Center line would most likely be CENTERLINE.

If you open your layer properties manager you can check the layer definition, and if you need to, you can change the linetype of that layer to centerline

in the layer properties manager.

 

The length of the lines created is defined by the ratio you set in the lisp, based on the diameter of the circle.

Layer defination on layer properties assigned as centerline but the center lines on circles did not appear as center line.

center2.jpg

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Dadgad

Then your problem is LTS (linetype scale), try adjusting that.

 

Write LTS at the commandline, it will reply with a number representing your current linetype scale.

To change it, just enter a new value, and hit ENTER.

You may need to REGEN, if you don't see an immediate change in the line display.

Edited by Dadgad
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