It's not the threads that make it difficult to remove & install the K10 upper burr carrier. The upper burr carrier assy.has two separate sections; the lower section that holds the upper burr & the upper threaded portion. The lower section is fixed in position by the small pin that fits into the groove in the threads so it does not turn. The upper threaded part turns against the lower section when you make adjustments or remove/install the carrier assy. As you found out it takes a bit of effort to turn the threaded section as it is drawn tightly against the burr housing by the 4 allen bolts that hold the upper burr in place. Having the top cover mounted to the burr carrier gives you the leverage required to turn the assy with little effort. Unfortunately with the "safety" roll pin in place you can only make 1 revolution. I've yet to own a grinder that had less need for a safety stop so that roll pin will be removed the next time I have the top cover off. With the upper burr fixed in place & the threaded section difficult to turn by hand I can't imagine how it could unscrew itself with the grinder running. Plus you still have the drag screw in the top cover that you can tighten down against the case to lock it in place.