I am trying to replace a leaking Mixet shower faucet. I've somewhat successfully removed the knob by breaking it off. Now I cannot remove the mixing handle/lever. The new one I purchased has a set screw. The original one does not yet it will not budge off the stem so I can get at the hex nut to remove the stem. Is the mixing lever suppose to just slip off? Could our hard water minerals got this stuck on? I have sprayed it with a very good lime scale remover yet it doesn't seem to matter. Can I just use a pipe wrench on the bonnet of the stem to remove the stem? Any help would be appreciated. Thanks.