Problem with overhauled steppers

I'm having a problem with a stepper that I overhauled, heres the
setup. I have 4 of Dan's 5 Amp stepper boards yes I've had them
for a while, they are working fine I think! I have a 37v 10amp supply
running the whole thing software is Desknc.
I bought 3 Sigma Inst. unipolar steppers way before this
list was around to get advice. They are or were 5 wire motors I took them
apart and brought out all 8 leads. About 2 weeks later the list discussed
not doing this without an iron core to avoid demagnetizing the motors too late
for me I was done by then.
Here is the problem no matter how I configure them in desknc when I jog them
from desknc or by running a small test program the motor just won't make a
complete step. The motors are size 42's rated at 12v 1.7a unipolar I'm
running them wired half-winding at 1.7a. The motor is on the X axis of a
shoptask 3 in 1 mill. Any advice? Is this caused by we overhauling these?