I have straighten many of them. Heat them up slowly to keep the threads in as good as shape as you can. I always leave them together. The end and center gives you something to press on. I also have a bronze block I put on the threads to push on.
When I get them straight I then take it apart. Then I reheat the straightened area to cherry red. Then slow cool it in a bucket of oil. Dip it in and pull it out. Few seconds in and 5-10 out. This will heat treat it but not to glass hard like watered cooled will do.
Then I have a set of thread files that I use to clean the threads up with. You usually can get them to work as good as new if you take your time.