Although at times when making the flea circus chariot I had to use a magnifying glass I never actually did any machining using it.
John R. Bentley has rigged up a LOMO MBC-10 (LF-100) stereo microscope in his workshop which can be used with to assemble miniature components or with his Taig 4500 Micro Lathe. I’ve got some A5 sized fresnel lenses (page magnifiers) that give me 2x magnification which might be handy when setting up tool height etc, it’s something worth experimenting with as it would only need a very simple stand.
John has also made a scale working model of a Taig lathe with working hand dials and four jaw independent chuck. I’m impressed with how he made microscopic tools from materials like piano wire which were then used to engineer the model. It makes my efforts of working with M2 Taps look positively gargantuan.