Thread tolerances differs from Ender3 pro and Prusa
I have an ender3 pro where I print thread on a 14 mm bold and nut. I reduce the thread so to have a tolerance that the nut fits, but if I print his on my new prusa it is not interchangeable with the printed parts on the ender. the bold is too lose, and the bold from the ender does not fit
we use that to hold a telephone to make automatic pictures of trash I make a lot of these holders and I want them all the same so that all part fits.
I tried a lot of setting but noting is really good (the same) too loose, too tight
Do the nut & bolt printed on the Prusa fit together properly? I suspect you are finding that the Prusa prints more precisely. Less tolerance is required between the nut & bolt. You're in the interesting position of trying to make your more precise Mk3 print like a less precise Ender 3. Your best bet is probably to match nuts & bolts from the same printer for each print.