I done my apprentiship on these. The sledge hammer remedy is the go. The tapers will have a split in them. Usually once they loosen with the hammering, you have to put a screw driver in the slot and wind them off. I had a pair of slip jaw pliers in my tool box that I ground one of the jaws to a tapered point. If you use the tapered point in the slot, it opens them up and with the other jaw opposite it, they come off really easy.
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