Extension lines for a radius dimension need to start at the center

Having used another CAD program for several years, I was used to the idea that all radius dimensions, like of a given arc, would easily start at the center of the arc, thereby denoting the position of the arc's center.

I'm slightly bugged with some CAD users, even books on the subject by autocad users, that give an arc's dimension from the outside of the arc, yet fail to show the location of the arc's center when it may not be self explanatory. Not good dimensioning practice from what little I've been schooled...

So, in AutoCAD 2007, how do I get an arc's radius dimension line to start at the center and point out to the edge. I can do all kinds of things to the position of the text, etc, but can't figure how to get it to start at the center. (The dimension line needs to start at the center.)

Thanx.

Dave N

I think you have to modify your dimension style, Fit, Text Placement, to be shown over the dimension line without a leader. For the center mark you'll have to place that separately. Look under Dimension, Center Mark.

Actually ReMark, ACAD will place a center mark for you with the radial dimension, just make sure you have it selected in the "Symbols and Arrows" tab.

As for what dniemeye wants:

Other than exploding a radial dimension and manipulating it that way, I'm not sure what to tell you. What you're after is not a way of dimensioning I ever learned.

-Crom

Hmmmm..... You've never heard of showing radial dimensions like this? See attachment. Like the 1 7/8 arc. Not that all arcs would have to be dimensioned like this, but sometimes it's required for clarity. If you DON'T denote where the center is along with the dimension line starting from the center, especially in a rather complicated drawing, it's almost impossible to know where it is without this method. Just showing "center marks" sometimes isn't enough 'cause there might be several centers of circles and arcs next to each other. Denoting the center along with the extended radius dimension line does just the ticket. It was common practice in hand drafting (like this very OLD book that the picture was from) and seems to have gone by the wayside by many CAD programs or is ignored by many draftmen... I've seen plenty of AutoCAD drawings in tutorial books where they do too simple of arc dimensions and I've had to tell my students "that's the way to NOT do it..." but seems to be common practice today for AutoCADer's, not with many other CAD programs like I just left (Microstation).

So my question remains: How can I get a radial dimension in AutoCAD 07 for an arc like shown in the attachment? (I feel really stupid 'cause a student started one project from scratch and his radial dimensions were always like I show in the attachment, and we couldn't figure it out. Couldn't change the settings, so I had real egg on face...)

Dave

Setup your dimension style to align the dimension with the dimension line.

Once you place the radial dimension on the drawing, select it, right click and select "Dim Text Position", these select "move text alone".

OK, now I see, that is indeed how I learned them, I just misunderstood your original question.

-Crom

Thanks guys for the help. That editing of text method was just the ticket. Sorry that I didn't specify what I wanted better ealier. I said extension lines and meant dimension lines. What a goof ball I was...

Now one more related question: Like I said before, a student of mine stumbled into a new file and the dimension style was totally different. Every time he dimensioned a circle or radius it was exactly as I was asking for in this original post, with dim lines starting in the middle of a radius or a circle diameter always in the middle of the circle. But we don't want dimensions like that every time. SO, how do you turn that off and on (or set up two styles) without having to edit every radial dimension? There must be a setting in dim style that I'm missing.

When your students start a new drawing, they may use the ACAD.DWT or ACAD-NAMED PLOT STYLES.DWG template. You can open each of the templates and make the change in the template and save it back to the template folder.

You could also create a standard template that they must use on all their projects.

For example in my introduction to CAD course I require each student to create a template named "OCCC Layout Template.dwt. They use this for all assignments. (I want them to know how to create a template, not just use one.)

Just an idea. I used sometimes the command DIMJOGGED to dimension arc and with this the dimension line start from the center.

Or did I missunderstood the problem?

Thanks guys for the help. That editing of text method was just the ticket. Sorry that I didn't specify what I wanted better ealier. I said extension lines and meant dimension lines. What a goof ball I was...

 

Now one more related question: Like I said before, a student of mine stumbled into a new file and the dimension style was totally different. Every time he dimensioned a circle or radius it was exactly as I was asking for in this original post, with dim lines starting in the middle of a radius or a circle diameter always in the middle of the circle. But we don't want dimensions like that every time. SO, how do you turn that off and on (or set up two styles) without having to edit every radial dimension? There must be a setting in dim style that I'm missing.

'DIMSTYLE' on the command line and the Dimstyle Manager will pop-up.

Highlight your current dimstyle on the left, select NEW on the buttons to the left. A new box will pop-up "Create New Dimension Style", select Radius Dimension (or whatever you want to change) in the "used for" dropdown box. Select the "continue button" at the bottom. Adjust the settings to your desire, when finished select the "Ok" button at the bottom. When finished close the Dimstyle Manager.

So my question remains: How can I get a radial dimension in AutoCAD 07 for an arc like shown in the attachment? (I feel really stupid 'cause a student started one project from scratch and his radial dimensions were always like I show in the attachment, and we couldn't figure it out. Couldn't change the settings, so I had real egg on face...)

 

Dave

All dimension styles are defined from the "Format" drop-down menu. Firstly the dimension shown is "Centered" with the dimension line, ie not "Above", which you can select on the "Text" tab. Centre marks are selected on the "Symbols & Arrows" tab.

Having said that I can't see it makes a blind bit of difference. I never use centre marks because they clutter the drawing in order to state the patently obvious. The centre of the radius can only be in one place, ie 'R' from any point on the radius. It wouldn't be a radius otherwise, and if it wasn't concentric to the bolt holes it would have dimensions specifying the eccentricity. For the same reason I never type 1.0 when 1 will do. I'd be much more concerned that your student is using imperial dimensions in what is generally accepted to be the 21st century.

Boro Nut

Thanks for all the previous posts because they enabled me to find the complete answer..

Steps:

If one is particular that the setting should be only for radius dimensioning, then follow SLW210 at the outset..(Under Dimension Style Manager, select the dimension style we are currently using. Select NEW tab. In the 'New Dimension Style' box, select 'Use for' and change it to 'radius dimensions')

Now under the new created dimension style(it appears as child in the tree), click modify tab. Go for the fit tab, select 'TEXT' or 'ARROWS' or 'BOTH TEXT AND ARROWS' instead of 'either text or arrows(best fit)' in fit options.

I suppose this solves the problem.

(this is my first post and hope it helped you guys)

What's the big deal here, isn't this something that you'd simply use DIMRADIUS for? If you need the 'R' after the dimension, instead of in front, that's another issue.

Not to hijack the thread, but I thought this was the original topic.

When I use radial dimensions, it's usually to show the radius of a curb. Often we will specify a staking point at the center of that radius. I would like to draw a radial dimension that has the arrow inside the curve and a mark at the center. From what I've learned through research and experimentation, the center mark only shows up when the arrow is outside the curve, and there's no way to position the end of the dimension line at the center. What I have to do is draw the dimension, explode it, and adjust the pieces as needed--which defeats the purpose of using the dimensioning system.

Edit: I'm learning these obtuse little things, slowly but surely.... Now I'm using a point for the center of the curb and letting a point table take care of northing and easting. I looked closer at this thread and got a style that goes to the center. Apparently, though, there's no way to modify a dimension style to make it for radius only, so you've got to delete it and start over? Thanks, Autodesk.

Change Dim Text position into Move text alone and put the value above or centered the dimension line.

I used to deal with what the OP was addressing. The fix is.....

AMOPTIONS-----Enter

Choose AMStandards

Double click Dimension

Under Default Representations choose Radius or Diameter-----I set both the same

Make sure the box is UNCHECKED for: When dimension text is inside, hide dimension line inside large arc/circle.

Don't forget to hit all of the Apply buttons on your way out.

This will give you a dimension line that starts at the center of your arc or circle and heads out radially to the edge.

I am not sure if my question is related, but I am trying to figure out how to do a radial dimension inside small arc without radial extension (past center of arc).