I was given a portable receiver with a damaged telescopic aerial, the set had been dropped and one section of the aerial had become slightly buckled. and wouldn't telescope inwards. I first thought it would have to be either left protruding or written off and replaced with the nearest substitute I could find, but later examinatuion suggested it might be repairable.
The first step was to remove the finial; this had been screwed on tightly and locked with some sort of compound. By gripping the finial in a collet chuck on a lathe and the top section of the rod with a strong pair of water pump pliers, I was able to revolve the chuck by hand and unscrew the finial.
The next step was to find a collet that was a reasonable fit over the damaged section. By screwing up and unscrewing the chuck ring I was able to make the collet gently pinch the damaged area down onto the next rod inside it - gradually working my way along and back until all the creases had been removed.
Although the result didn't look perfect, it slid in and out easily enough. It just remained to screw the finial back on, with a dab of varnish in its threads.
Job done - cost nil.