Final Tightenin - Warp Threads
The warp thread should be really tight. Tight enough so they "sing" when strummed like a guitar. What I do is insert a screw driver or similiar strong bar into one of the open holes that run thru the base and slider. The wing nuts, at this point, are tight, but not to tight that the screw drive, when turned so as to move the slider and tighten the threads. Often takes two people to do this since after the threads are tight, you have to tighten the bolts by holding the wing nuts secure and tighten the bolt cap with with a socket wrench. Seriously, you don't want the slider to slip, EVER.
I believe you can purchase a loom on line which will work just as good as my homemade one. I just didn't want to spend the $100 plus for one. I figured "I built my own house," I should be able to make one of these. LOL