I'm having desktop mini 3d printer that I always need to manually adjust the nozzle gap to bet with 4 screws. Currently I move the nozzle all over the bed area to see any touching/scratching on bed with naked eye and hand feeling to avoid any touching.
I'm wondering what should be the correct gap between nozzle to bed? by the way I use 0.4 mm nozzle. Is there specific gap or tool insert to check gap correction?
Use some A4 paper sheet to adjust nozzle to bed plate gap of your 3d printer. You can lie A4 paper on top of bed and adjust the bed height in order to move nozzle lightly touching/feel with A4 paper. This may give you better result.