K people, lets not forget what the problem is.. most likely its due to the fact that the threading is stuck from gooey THC trichs... what is THC? a fat. Now, how are lipids soluble? in either more fat or alcohol (thats why soap is fat and another agent)...

Try either some rubbing alcohol, and/or heating up the part of the grinder... the heat combined with the dilution of the trichs and plant matter should be enough to open after a little force is applied...