Wacky UCS

Just when I thought I had it figured out, this UCS thing throws me a curve.

I'm trying to draw a circle at the end of a line I created so that I can extrude the circle along the path of the line. The line exists and then I set my UCS to have the XY plane perpendicular to the line, the Z axis then runs parallel to the line....follow?

I then try to draw a circle and choose the end of this line as the centerpoint for it. The ucs then shows up but it's rotated out of the plane I just set it in and I cannot draw the circle like I want it. I can draw the circle somewhere off in the 3D space and it forms like I want it, but if I choose the end of this line as the centerpoint the UCS rotates and I end up with a circle not in the plane I'm intending.

Is there some variable that got set to the wrong value that I need to change?

I have two lines in this sketch that I want to PEDIT into a single polyline. But when I attempt to do this it says the lines must be coplanar.

When I check the properties on the lines, both of them have a Start X and an End X of 1/4.

I'm still new to this but I just don't get why this lines would not be coplanar if the Start and End X's are equal for both lines.

Not sure about the ucs problem, but when i get the non-coplanar

issue i go in to the "Draw" drop down list and select 3D Polyline and

trace over the sections that are not joining.

I'm pretty sure there's a better way but as haven't done much 3D

that's the best I can give.

Hopefully somebody with more brains than me will have a better

answer

Yes, that's what I figured out too and that's what I did to get the results I wanted, or at least what I think is the resultes I wanted.

What's a bumer about this is just as I thought I was really understanding AutoCAD 3D practices, I'm hit with something like this. I'm no geometry major so perhaps there is something I'm missing here but if two lines have the same Start and End X values, they should, IMHO be coplanar.

you'd think - this problem used to drive me round the bend when was at college.

Is there some variable that got set to the wrong value that I need to change?

Perhaps. Try setting the UCSDETECT variable to 0.

Thanks for all the replies. But here is the problem. I quit doing drugs many years ago, but darned if I'm not seeing this happen more than once so it cannot be halucinations.

I am drawing a set of simple stairs in 3D. There are several runs of steps which make 90° angles to each other so I'm having to move the UCS all around. I set the UCS in the desired plane and orientation and then attempt to draw a circle. Expecting the circle to be drawn the XY plane, I chose the end of a line where I want the center of the circle to be and then poof...the UCS changes to show a different XY plane and the circle gets drawn 90° from the plane I want.

I have played around with UCSFOLLOW and that does not seem to be the issue. But for some reason my UCS changes once I select the end of the line to locate the center for my handrail circles.

Now last night it seemed to be selective on when it would work and when it would screw up. Because several of my attempts to get the handrails drawn would work. I gotta believe some variable is getting changed and I just don't know which one.

I found the problem was that UCSDETECT was set to 1. Funny it unless (1) is the default, I wouldn't know how else it got that way. I didn't even know of this variable until now. I don't think any of the AutoLISP files I run would do this but I cannot say for sure. In any case, once I set it back to zero, the problem resolved itself.