cant get new steel bushing to thread into new lower control arm

[Justins76]

I had to buy a new lower control arm that uses the steel bushings. I also bought new moog bushings. The problem I am having is how do I thread the bushings into the control arm since there are no threads already cut into the arms since they are new. I tried putting in the shaft, centering it, then screwing on both ends onto the arm. Once hand tight, I used my impact wrench but I can only get them in maybe 1/2 turn before they stop. Anyone have any tips? Thanks