What do you mean by “round”? As in: the crests of the threads round
over? (on the rod, or in the hole?)
Do you have an adjustable die wrench? If you look at some of the
dies (not all, but some) the round die is split, like a “C”, and
there’s a teeny little screw in there to tweak the gap in the “C”.
Which tweaks the size of the thread, ever so slightly. If so, yours
could be mis-set. Probably too far open. (There are reasons why you
might want to do that, but unfortunately, they don’t normally
mention that the dies can be tweaked, so nobody realizes what’s
going on if they get out of adjustment.) Sometimes there’s an
adjustment screw on the die wrench too, so you can tweak it twice,
if you’re not careful.)
What thread size and pitch are you using, and could you send
(A) your setup,
(B) the threads as cut, and
© the threads after they ‘round’?