Rounded stem ends....

I have a 2 knob shower setup with stems. The stem ends are rounded out so they dont accept the original style handle any more. I bought some Danco aftermarket handles that utilize some allen screws on an adapter to bite into the stem end and then their shower knob slides over. They dont seem to work that well. Should I try another brand besides Danco for this application, thinking their adapter design is better? Perhaps the stem ends needs to be sanded a little more round? I prefer not to have shut the water down in the apartment building to replace the entire stems with new ones. Thanks!!

If you want a permanent, solid fix, you will have to replace those stems. There are different types of retrofit handles but they all have the same problem; they are trying to connect to a round surface with no grooves/splines to make a secure connection. If you're determined to use those cheap handles, JB weld them or epoxy weld them to the stems, that is about the only thing I know that will hold them on. I personally would shut the water off and do it right, replace the stems and buy the handles that were designed for it, no more rigging. Just remember, you weld those handles on, you must break the handles off or cut the stems behind the handles to remove it to replace washers. Either way you will be replacing those stems..one way or another.