This was my first print after assembling my Prusa (and obligatory beer opener), just to realize, its too high in lowest position. So ive remodelled it in fusion after got some basic skills. The silver one is original, black is my make. 

Better to use some greas to help clear that thread, ive snapped first one. Its tight at first, but if you screw/unscrew few times, it will be just fine. Or you could use M15 screw at first to clear it. 

Its alchemy to adjust functional thread for newbe like me. :)