Hey im using the latest version of blender as of march 2018
I made a custom wall plate for a relative to 3d print. I made sure to set units to "Imperial" and "Inches" as i needed a piece that is 1.5" square. here is a picture of my current settings
As you can see i have my scale set to 1.5" but the problem happened when i shared the file (a .STL) with my relative and they printed it it came out as 1mm wallplate, so if their is anyway to tell blender or the exported stl to be in inches that would be great! thanks guys