I came up wtih a trick that worked quite well for me. I needed a solid shat pot and I only had a split shat CTS pot. Uhmm... I could align the gap with the screw but then the knob would not be in the right place. I needed another solution... I decide to fill-in the gap/middle with some card to avoid any movement of the shaft and then place a piece of heat shrink tubing over the shaft to cover the whole thing. Snipped off the excess of the tubing from the top using a Stanley knife and presto! solid shaft is is now. Totally reversible mod too.