There is no direct way from Revit to btl and not planned for as can be seen HERE.
So you would have to look at the other end (CNC machine software) to see which files it can import.
Might be that exporting to dwg from Revit is an option, as this is a common file format that many software will read.
Also note that Revit is mainly used for designing buildings and not really suitable for product design. Probably other software might be much more useful in this respect (something like Autodesk Inventor)
Louis

Please mention Revit version, especially when uploading Revit files.