But how many times have you had the rod spin as you try to make the cut only to crush the threads when you tithe jaws of the vice? Or simply endup with a mangled less-than-straight cut? Here's a simple way to make this job a lot cleaner.
Instead of clamping the threaded rod directly in the vice, I use an ordinary wood block that I can tighten in the vice, see drawing above. The rod passes through a hole drilled near the end of the block. And a thin kerf guides the hacksaw blade while I make the cut.
Already this is an improvement. But you can also prevent the rod from spinning as you makethe cut, by threading a nut on each end until it's snug (but not tight) against the block, see Detail 'a.'
The nut remaining on the cut-off piece can be used to clean up the threads damaged by the saw. To re-cut the threads, just remove the nut as shown in Detail 'b.'
Ted's Woodworking - Guide eBook