Autocad 2015 units problem

[Anonymous]

I have very strange problem with Autocad 2015 units. When I enter command "units" it gives me "Drawing Units" dialog, where I can choose betweeen various units. I select "milimeters" and then I draw a circle with specified diameter of 10. After that I enter command "units" again and switch to "inches". I draw another circle with specified diameter of 10, and it is visually absolutely the same as previous circle. I've expeted it to be 2.5 times larger. Whats the catch?

[imadHabash]

Hi and welcome 

this drawing units dialoge is for insertion aims NOT for puposes as you expect. for selecting units and see real different you have to type and change sittings from   -UNITS 

Command: -UNITS
Report formats: (Examples)

1. Scientific 1.55E+01
2. Decimal 15.50
3. Engineering 1'-3.50"
4. Architectural 1'-3 1/2"
5. Fractional 15 1/2

Good Luck..

[Anonymous]

Thanks for answer but it's still pretty unclear for me. I've already tried -units but it gives me to choose units format scientific, decimal, engineering, arhitectual, fractional and to choose if my angles will be in radians, degrees, etc. It doesn't ask to switch between mm, inches, feet, etc. 

[Anonymous]

I want to change my units to milimeters, so when I draw a circle and enter 10 for diameter, I want it to be 10mm wide. After that I want to switch the same way to inches and when I draw a circle with same method I want it to be 2.5 times larger. Is this possible?

[wispoxy]

Set your workspace to 1:1 ratio.

[Anonymous]

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@Anonymous wrote:

Set your workspace to 1:1 ratio.

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Can you explain more further how this gonna help me?? I need to change units, not workspace ratio. 

[Anonymous]

I don't know if I'm asking something stupid or unlogical... I need very simple thing. How to change document units? I need to switch between units while drawing. I don't understand what workspace ratio has to do with this?  I need to draw multiple parts in my drawing, for some I know measures in inches, for some I know them in milimiters, and I don't want to do conversion each time.

[sthompson1021]

If you use the -DWGUNITS command, you can switch what the units are but you need to make sure that you answer no when it asks if you want to scale objects that are in the current drawing.

Edit: The answer should be yes

[GrantsPirate]

From help file

"Objects are measured in drawing units. Before you start to draw, decide what one drawing unit represents in your drawing.

Create your drawing at actual size consistent with the drawing units that you want to use. For example, the objects below could represent two buildings that are each 125 feet long, or a section of a mechanical part that is measured in millimeters."

[steve216586]

You cannot jump back and forth, with the drawing units, on the fly. If you have a metric unit drawing and want to draw imperial unit objects, you will have to convert distances either before you draw or scale after you draw.

As mentioned, the units must be established prior to drawing the first line. Establishing the units in a drawing is what dictates the format for the direct distance entry. Autocad uses a cartesean coordinate system. This means a model space unit may be specified as any distance. (mm, inch, foot, meter, etc) But once the unit is set, that is what Autocad will interpret each drawing space unit.

As to your experiments with changing units, -units, etc and nothing appears to happen...everything is scaled equally. If you receive an imperial drawing and wish to draw in metric units, you MUST scale the objects in the imperial drawing first. Just changing the setting UNITS -UNITS or _UNITS won't do anything to objects already present. Those commands only control objects inserted from that instance and beyond. They also don't change your dimension setting from imperial to metric.

[Anonymous]

Thanks everyone for trying to help, things are a bit clearer to me now 🙂 As far as I understood, I can draw objects using decimal numbers as measurement and once I change units (via "units"command) it will count all decimals as milimeters, inches or whatever unit I choose. Is that how it works?

[Patchy]

Then you have to know how to set up dimensioning to get it to the unit you're working on.

[wispoxy]

You can throw units off after selecting meters, inches, or whatever. So you need to set a ratio of 1:1. Not the workspace view ratio, the project ratio.

[wispoxy]

If you want to jump back and forth between units, create macros.

[kasperwuyts · Accepted solution]

The basic philosophy of Autocad is that you drawing is essentially unitless. When you draw a circle with a cirfumference of 10, it is not 10 inches, 10 cm, 10 light years wide. It's simply 10 units wide. The only time actual physical units enter your work is when you plot (in the plot dialogue box, whether it be in mode or paper space, you eventually have to convert units to mm or inches)

As a person working in metric this is quite intuitive since the base 10 system works for all possible units, including the generic 'autocad unit'. If you work with a base 12 system like inches/feet, I suppose this doesn't really make sense because a generic unit obviously isn't a generic unit if you add inch and foot symbols. It's something I refuse to think about too much, as the future obviously lies with metric anyway.