I have an inch based drawing.
But one of the holes is actually an even number of mm , and for a metric part.
I know I can override the text of the dimension to read the metric value.
Is there a way to set an individual aligned DA to display metric, imperial, or both ?
Hi,
One can search in the forum, this topic is already addressed numerous times. 
Example: 45 in mm is indeed a value hard to express in inches: 1.7716535433070866141732283464567…
Certainly when it should be 45.0000… but inches rounded to a number of decimals will be within tolerance.
Then use a custom decimal format for that Dimension, a Style override.
All values in CAD are typically unit-less.
A value is expressed in the global drawing unit.
1.23 may mean 1.23 mm or 1.23 inch or even 1.23 km, all depends on the drawing unit.
With QCAD it is not possible to mix drawing units in a drawing or to display 2 or more different units for the same Dimension.
Simply because any measured value is unit-less like any other value.
One can convert drawings into another drawing unit with: menu Edit .. Convert Drawing Unit (CU)
Then present two drawings, one in mm and one in inch.
It is common to include the drawing unit, scale, revision and so on in a title block.
Values in mixed but unnamed units on the same drawing is a ‘no go’, one would not know what the value 1.23 stands for.
Replacing the Label property with a text expressed in mm in an option.
Such a drawing would include a note in the sense of: “All measurements are in inches unless otherwise stated”.
For a single or a few Dimensions on a drawing in inch:
Use ‘<> in (nnnn mm)’ in the Label property of the Dimension (without the quotation marks).
Where ‘<>’ stands for the actual measured value as formatted in the drawing unit.
Everything else is custom text, ‘nnnn’ would then be the ‘even number of mm’.
Important here:
The measured value adapts on changing the Dimension reference positions, the ‘nnnn’ is plain text and does not adapt.
When considered as solved, please add [SOLVED] to the title of your initial post at the top by editing it.
Please also revisit your other topics as none seems to be considered as solved.
Regards,
CVH