Help - How do I remove caps on steel rods

[Kent]

I need to replace the bow rubber roller on my boat trailer. I thought it would be an easy task to remove the bolt, but I discovered it doesn't have a threaded bolt it has those kind of metal caps that one taps on to the end of a steel rod. I have attempted to remove one of the caps but without success. On each end there is a short rubber roller and then on the inside there is one longer roller. The outside rubber roller prevents me from getting a good grip on the outside of the cap to work it off. I tried drilling a hole in the center of it so that I could attempt to drive the rod forward and in the process pop off the cap, but every time I attempted to drill the cap my drill bit slides off. I have attempted to use my punch to make a starter point, but that cap is apparently made out of extremely hard material. Perhaps if I had a large pair of needle nose pliers I could grip the outside lip enough to work it off. Does anyone have any other ideas?
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