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Draw an Arc to Length
Tip# 4218 By Jerri Thompson On 25-Nov-2013
Rated By 0 users
Categories : Curved Objects
Software type : AutoCAD 2014
Rename File To : No Files to download.
This AutoCAD command allows users to draw an arc with a specific length.

Editor's note: If you cannot see the backslashes in the macro code in the tip below, please refer to the two highlighted portions of this image for correct placement; there should be two slashes as indicated by the first highlight, then one slash at the second highlight. 

Tipster Jerri Thompson created a new AutoCAD command that will allow users to draw an arc with a specific length.

"There may be a way to draw an arc with a specified length in AutoCAD 2012, but if there is, I could not find it. I created another button. It asks for center point, start point, and length of the arc. It draws the arc using your desired length as the chord length, then changes it using the length command:

^C^Ca;c;l;(setq L1(getstring"Enter Arc Length:"));ID'@;(setq P1(getpoint));@;len;t;!L1;!P1;;

"I hope you find this useful. I know I do."

Notes from Cadalyst tip reviewer Brian Benton: In the ribbon there is an ARC button. It has an option arrow. Click it to get options on the ways to create an arc. One of them will allow you to draw an arc based on length. Or start the Arc command on the Command line by typing ARC. Pick a start point or type C to create the center point of the arc. If your first point was a starting point, then make your second the center. Then type L for length and type in the length. If you start with the center, then a start point, then type L for length and type in your length. The command macro created in the tip automates this process. Most commands have more options available to them. Keep an eye out for those options in the Command line.


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User comments
Comment by Cooper,Kent
Posted on 2013-11-25 09:39:59
See also Tip #3392, "Arc Length" [one of several with that title, so go by the number]
Comment by Smith,Rob
Posted on 2013-11-25 14:29:04
Brian, your notes miss an important point - after automating the process of setting a length for a CHORD, Jerri's macro then calls the LEN command and sets the Total length of the object to the exact value desired. An arc is longer than its chord, and the ARC command only allows the user to specify CHORD LENGTH. Also, the macro as printed is missing two back-slashes collowing the "c;". Finally, users may want to start with "^C^Carc;" for those whose PGP file has reset the alias "a" to other commands, like ARRAY.
Comment by Vuchkova,Galina
Posted on 2013-11-26 03:08:49
Rob has right, you cannot draw a arc with a specific length because the option L for the Arc command is the length of a CHORD. But you can draw a arc with random length with the radius and and center desired and then change the length with the command LENGTHEN - Total to the desired value.