Changing units of measure

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 From:  mickelsen
4131.1 
I'm sure that this is an easy thing to do but I'm doing something wrong and I don't know what. I have a drawing that has "inches" set for its units. I would like to be able to change the units to millimeters and be able to see all the measurements come out it millimeters correctly. Is this possible?

Thanks,
Mark
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 From:  Michael Gibson
4131.2 In reply to 4131.1 
Hi Mark, first go check your settings under Options > General > Unit options, it's this button here:



In the small dialog that comes up, pay special attention to the "Scale on unit system change" checkbox, you want to make sure that is turned on (checked). It is checked by default but maybe you've turned it off at some point? That dialog looks like this:



You can also change the default unit system there which controls which units are used when you initially start up MoI, unless you have set a template file in which case the units in that template file will be used.

Then go to the Unit system dropdown in the main Options dialog, here:



That controls the unit system setting for the current document (as opposed to the startup default units which what the setting on that smaller dialog controls).

Now change that from your current Inches setting to Millimeters instead.

That should change the current units and also scale objects into the new unit system as well when that one checkbox mentioned above is enabled. So for example in if you had a box that was 1 unit in width in inches, when you switch to mm with that checkbox option enabled it will become 25.4 units across after the unit system switch, since 1 inch = 25.4 mm

You'll probably want to leave that "Scale on unit system change" in its default enabled state normally, the only time you'd really want to disable it is if you want to switch unit systems while having everything maintain the exact same numeric coordinates (like a thing 1 unit in size staying 1 unit in size even when the units change), which you normally only want to do if something was done in the wrong units initially and you want to change the units label and nothing else.

Hope this helps! If you're still having problems maybe you can post the model file so I can give it a try over here.

- Michael

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 From:  mickelsen
4131.3 In reply to 4131.2 
Hi Michael,
I've included a drawing. The rail was created at 30 inches long. I followed you instructions to change the units to millimeters, but it comes out saying that the rail is now 30mm long. I believe that is should be 762mm.
What am I doing wrong?
Thanks,
Mark
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 From:  BurrMan
4131.4 In reply to 4131.3 
If you have a file that has no unit system, then change it to milli's, there will be no scaling happen.. It will now just be 30 mm... For the file you just posted, I made a workspace of "no system units" then "Imported" the file in.. I set the units to "Inches" which set the rail at 30 inches. Then I set the units to millimeters and the rail was scaled to the 762 mm you were looking for...
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 From:  Michael Gibson
4131.5 In reply to 4131.3 
Hi Mark, it looks like the file you attached there was saved after you switched the units to mm.

Could you please post the file _before_ you switched the units to mm so I can take a look at the original file? Did your original file actually have units set to inches, or was it possibly set to "No unit system" ? Because if was set to Units = "No unit system", then it would behave like you are describing since like Burr mentions switching from "No unit system" to a different system does not apply any scaling.

So if that's what you are running into, first switch from "No unit system" to inches, and then switch from inches to mm and that should give you the scaling you want, as long as the option "Scale on unit system change" is enabled.

- Michael
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