Problems with motor stalling due to motor/lead screw alignment

Has anyone had trouble getting the Lovejoy couples to line up?
I've got everything straight as far as motor mounting to lead screw alignment but the problem seems to be when i tighten the setscrew on the lovejoy couple to my 1/2 inch leadscrew it will either cock slightly sideways or move the screw alignment slightly off center. I'm coupling from 200oz steppers that i got with my Hobbycnc kit and the 1/4 inch couples seem to snug up onto the 1/4 inch shafts of the motors without causing the offset problem. The lead screws are 1/2 inch allthread and are pretty snug going into the 1/2 inch Lovejoy couple but i can't seem to get them to stay straight after tightening the setscrew. Ive tried to grind a flat on the area of the leadscrew where the setscrew will engage but still seem to be getting about 1/16 to 1/8 of an inch of endplay once the spider is inserted. The end result is that the motors will stall after a partial revolution because of the offset. At this point i'm open to any suggestions because i'm really ready to see this whole thing start making some chips.

Thanks,

Scott

Use a smaller couple half and machine the end of the screw.

I've just installed my Lovejoy coupler and I'm getting 93 ipm with no problem stalling or mis-alignment. The end to my xylotex motor is on the flat, my lead screw side is a so messed up on the flat area from trying the straight couplers that I had to use the rounded side and did not grind a new flat. I will do that now that it works nicely. Both of my ends are 1/4" btw.

Did you check the set screw in the coupler? Maybe it is a manufacture defalt? You said you ground it yourself, are you sure the flat is parallel to the shaft?

Good luck, I will posting a question momentarily on the other end, how to put nuts that don't slip. :)

Aric

Have you tried end machining your lead screws on a lathe?