Drawing Arc Length?
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Category: EN
Forum Name: AutoCAD
Forum Description: Discussion about AutoCAD and AutoCAD LT, viewers, DWG and DWF formats, Design Review, AutoCAD 360, add-ons
URL: https://www.cadforum.cz/forum_en/forum_posts.asp?TID=12965
Printed Date: 31.May.2026 at 22:58
Topic: Drawing Arc Length?
Posted By: ARCBOY
Subject: Drawing Arc Length?
Date Posted: 10.Oct.2018 at 19:54
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Hello all, newbie here with very little to none of formal training and have a question as to how to draw an arc length. We don't anything really crazy or complex but we do draw a lot of pipe related drawings and need to use circumferential arc lengthsa lot. I only know of two ways to make a specific arc length and both seem to be a little archaic. 1. Do the math and draw a start and stop point for a specific dia and then draw that arc length on that dia then snap the arc length dim. I can do this accurately within 0.0000 deg. 2. As slightly easier way is to draw a arc length (ex. 1.45) that is close to the desired length on that specific dia. Then highlight that arc and hover over an end point and select lengthen then type in difference (0.05) between the desired arc length (ex: 1.5) and the originally drawn arc length to get the desired arc length of 1.5. I have found this to only be accurate if you are really close to desired arc length other wise it will be off a few thousandths. if someone has a link or suggestion it would be much appreciated. If this belongs in another section please move or i can post it somewhere else. Thanks in advance.
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Replies:
Posted By: ARCBOY
Date Posted: 10.Oct.2018 at 20:29
| I think I know why option 2 is a little off since it seems to want to draw a chord length and not an arc length. |
Posted By: philippe JOSEPH
Date Posted: 10.Oct.2018 at 21:11
| LENGTHEN is the command as explained in the related tip 3789. |
Posted By: ARCBOY
Date Posted: 10.Oct.2018 at 21:30
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Sorry for my ignorance , but I'm not sure what related tip 3789 means. I see the LENGTHEN command, but it is references something about chord length. I can't do much with a chord length and need the arc length. |
Posted By: philippe JOSEPH
Date Posted: 11.Oct.2018 at 07:24
 Arcboy, the LENGTHEN command will modify an arc length to the desired value that you will enter on your keyboard.
Please see here above the steps of the command ( in french sorry ), note that you will have to select 2 times the arc to be modified. An other option would be to use the parametric constraints. PS The related TIPS are just in the low left of your screen.
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Posted By: Kent Cooper
Date Posted: 12.Oct.2018 at 16:08
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LENGTHEN command, Total option, enter your desired Arc length, pick the end of the Arc that you want adjusted [the other end will stay where it is]. Or, I made an ArcLength.lsp routine defining a command called ARCL to draw an Arc directly to a specified length -- available http://cadtips.cadalyst.com/curved-objects/draw-arc-length-0" rel="nofollow - >here< .
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Posted By: ARCBOY
Date Posted: 12.Oct.2018 at 18:39
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Yeah the LENGTHEN command seems to be the same as hovering over the endpoint and selecting, lengthen, then entering the extra length you want it to be. I clicked on your link and downloaded it, but it gave me something in a notepad. I'm not familiar with what an isp is, maybe you could help me out with that or explain how I can use the download.
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Posted By: Kent Cooper
Date Posted: 12.Oct.2018 at 19:00
Hovering over the end of a selected Arc only seems to let you set either the angle from the center toward the new endpoint, or the radius of the Arc. Neither is the same as the LENGTHEN command and its Total-length option, with which you can enter the specific overall length you want the Arc to be, and make it so, precisely. To use the draw-Arc-by-length command, start the APPLOAD command, navigate to wherever you downloaded the .lsp [and that first letter is a lower-case L, not an I] file to, and Load it. Then type in ARCL [the command name that it defines] and follow the prompts.
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ARCBOY wrote: