I didn't see this anywhere else, so I thought I would tack this on here - some notes on my recent experience trying to import DXF in inch units:
I made some 2D plans and elevations on Autocad 2016. When trying to import the files to Freecad, I could not get the ODA converter to work properly (some error about moving the dwg file to a path without spaces..), so I exported DXF files from Autocad. Before saving as DXF, I issued the -DWGUNITS command to be sure of the export units Autocad was generating. When I set the units to inches, I then used the 25.4 scale factor in the DXF import settings in Freecad. But when I imported the file, a door that should be 3 feet wide was 1,935'-6 1/2" wide. When I set the scale factor to 1, the same dxf file imported with that same door at 76'-2".
So then I tried to change the scale factor in Freecad to be the equivalent of 1/25.4 = 0.03937, but the best I could enter in the DXF import preferences was 0.0394 - only four decimal places. It was close to the correct scale, but this is not enough precision for reasonable architectural work - a few inches of error over 100 feet.
Back in Autocad I used the -DWGUNITS command again and converted the units from inches to Millimeters. Then I imported the dxf file into Freecad with the scale factor set to 1 and the import was perfect - a 3 foot door measured exactly 3 feet. A 76' length of wall measured 76 feet exactly.
So it seems to me that the scale factor guidance in the "mouseover" in the preferences may need to be reversed. And there needs to be a way to enter more decimal places for the scale factor. Perhaps there is a way to do this from the command line directly? It would be best to have it set up right in the GUI, but if anyone knows how to set this with more precision some other way, that would be helpful to know.
It's good to have some method to get things properly scaled, but it would be nice to be able to simply import from my large library of imperial unit drawings and have Freecad do the unit conversion without having to open 2d CAD and run a conversion. In a production environment, that's a huge chunk of time saved.
-israel smith
Smith Buckley Architects
www.sbavt.com
OS: Windows 10 Version 1909
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.19.24276 (Git)
Build type: Release
Branch: releases/FreeCAD-0-19
Hash: a88db11e0a908f6e38f92bfc5187b13ebe470438
Python version: 3.8.6+
Qt version: 5.15.1
Coin version: 4.0.1
OCC version: 7.5.0
Locale: English/United States (en_US)