how to create half - arc

[ReMark]

I have question, I want to create this, but any advice how to build that? and need what command to handle. any advice please!

 

You asked "What command to handle (create) this?" The answer is many commands as you no doubt are realizing. They include such commands as....line, circle, fillet, offset, copy, mirror, donut and a few dimension commands with dim aligned being a critical one along with dim linear, radius and diameter. You may also find Snapang and Polar Tracking useful as well.

 

Perhaps these next four series of images will help you understand one way to accomplish the task.

 

The process starts here. I used a metric template.

 

 

Next comes this.

 

 

Followed by this. Oops...I think 8 is just a repeat of 7. Sorry.

 

 

Finally we dimension the object.

 

 

Remember that this is just one of a handful of ways to accomplish the task. AutoCAD gives the user many different ways to do the same thing. It is up to you to find the way that works best for you.

 

Notice that I make use of different layers (with different colors assigned) for different entities. My layers included Object (magenta), Centerline (green), Construction (beige), Holes (cyan) and Dimensions (red). Create and use layers that have meaning for you.

 

My best advice for you is to get some training as you appear to be lost right now.

 

Good luck.

Edited February 11, 2015 by ReMark

[yaim229]

thanks, I'm from taiwan, chinese language, I use google translation to translation. maybe something ... may be not understand. I'm so sorry. that original image is for reference, boss request me to changed something. but major knowledge as same as that.

[ReMark]

There is no need to apologize.

 

What did your boss ask you to change?

 

Do you know how to do it?

[yaim229]

focus that offset, RO, lengthen, is vert helpful. but basic need knowledge that circle, 360 degree , maybe adjust need -90, -180, -270. +90, +180, +270, get that correct degree. is look fine, thanks all.

[ReMark]

What changes did your boss ask you to make to the drawing?

[yaim229]

maybe changed that width, that arc degree , total of that small circle some adjust.., if future some case I not understand how to do it, I will post again.

[ReMark]

You would do it much as I outlined in the images I posted previously. In the image above one approach might be to do half the object then mirror it to the other side to complete it. Do you understand?

[yaim229]

I understand. for first time to handle this job. even I got that CAD hardcopy. I not understand that YELLOW point why need? step by step, found that orginal line, finial , erase . so far I not understand that. but hardcopy show this information. maybe reason.

[ReMark]

Those lines appeared in the image you first posted so I recreated them. I refer to them as "construction" lines. Since I put mine on a separate layer all I would have to do is freeze the layer when it came time to print and they would not show up.

 

Do you have any dimensions to go with the image in post #26? Any angles or radii?

 

This is one way to get started. Draw half then mirror. Understand?

 

In this example I increased the width from 28 to 36. The green centerline is 18 units in from each side.

 

Edited February 11, 2015 by ReMark

[yaim229]

thanks, I not undetstand how to Draw half then mirror. begin, I use very bad method handle "construction" lines. , left to right (150 degree, line 180, 30 degree)

[ReMark]

If you do not know how and when to use the MIRROR command then stop what you are doing and go through the tutorial here at CADTutor about the Modify commands and/or read about the command in your AutoCAD Help file.

[yaim229]

thanks, I found that how to used mirror, is it helpful command. also that rotate command, also helpful. both. I known how to used.

[yaim229]

Now, I have some part, not undetstand, how to make this. any advice please!

sw1.dwg

[ReMark]

You should not be dimensioning your drawing as you are going along. First finish all the geometry. When you are done and have verified it is correct then do your dimensioning along with any callouts (notes/text).

 

By the way, what did I tell you about using layers? You should not be putting everything on one layer all using the same color. Have a layer for geometry and one for your dimensions at the very least. It will be easier to distinguish the entities if each layer is assigned a different color too. Do you understand?

 

Next thing I noticed is you used the radius of 300 for the wrong line. Look at the image you posted. That radius should be applied to the arc on the right side not to the arc on the left side.

 

Can we get a close up view of the end that you circled please? It's difficult to see exactly what is being dimensioned. Also, it looks like some dimensional information is missing for that end as well. You need to find out what it is. Thanks.

 

OK, I noticed something else. I think you have misread the image regarding the distances 140 and 165. They are to the point of intersection of the tangent lines.

 

My recommendation: Erase what you have and start over.

Edited February 14, 2015 by ReMark

[yaim229]

thanks., that close up. that layer is it: that drawing that lines used (white) that dimensions use (RED) color that construction lines used (BLUE) color that? I not undetstand that Left/Right, if again see that hardcopy, how to draw it? is it used offset and RO that command to draw that arc?

[yaim229]

here, redraw again. I want to draw that green circle. first. am i correct?

[ReMark]

Yes, draw everything in the green circle first. Do NOT dimension anything. You do see what the 140 and 165 dimensions are referencing don't you?

 

 

Missing info at the end of the object includes a distance and arc information. It's possible there is even an angle that is missing but I can't be sure. Without the necessary information the drawing cannot be completed.

[yaim229]

for my undetstand that circle rule, my step is : draw line 165, degree 152, line 140 offset 90 arc rotate mirror lengthen 165 to 140 lengthen 140 to 165 offset 300 ro 169 offset 300 arc. EDIT: I not sure that value, I think 80 is fine, also ending, not ARC, line is fine. but I not understand that left (R20. degree 150, 1.5) and right (3 that blue lines) what mean of that?

[ReMark]

You draw the right side as a series of three lines (140, 165 and 80 units in length). Join them using the PEDIT command to create a single polyline. Offset that line 29.5 to the left. Then go back and using the FILLET command apply the radii of 90, 119.5, 300 and 270.5 and you are ready to move to the next part of the drawing.