hex nut

I have printed several things with inside threads and they turn out fine sometimes a little stringy the key is have everything dialed in especially with regard to overhangs.

What z res are you trying it in and what size nut?

I've tried printing a few and the best method I've came up with is printing it is to the relevant ISO/BS/ASME standard or whatever and then running a tap/die over them...

For me at least, I notice that getting down to an M8 size is about the limit that I can go without shearing the stud easily during tha tap/die process....that is...IF the stud is printed with the hex on the bed..........printing them lying down on the bed makes them ALOT stronger but not near as pretty.

i pretty much print everything at 0.2mm z height too.

.........std. thread charts show sharp edges.......
filament is naturally rounded.....
so you wont get a true thread without a tap/die being used post printing....

sure it'll screw on; but with alot of friction present...think of a nyloc nut..

EDIT: When printing threads that I run over with a die/tap, I switch ON the randomise start point setting if possible...(by default I leave this off as I think the quality isn't as nice with its left on....)  its far easier to cut the thread than having them all lined up when the setting is off:)...:)

In my experience, if you want perfect threads you need to print at .1mm with a fan mod.  I have a picture posted somewhere of an example.

Here is one I did at .3 the settings were a little off but only has about 5 minutes of exacto trimming(had a few strings) and been threaded together once.

Nope...