Didnt like the idea of regular threaded rod and didnt like the way the nut was retained. So I changed the end carriages to use an M8 acme leadscrew and brass nut thats readily available on Ebay from multiple sellers. Also includes a modified tensioner bracket. works with a 1/4-20 square head bolt. bolt is inserted from the inside and a hex nut or threaded thumb wheel is added on the outside for tension adjustment. EDIT 9-6-15 I had to remove the idler bracket. the bore for the linear bearing was the wrong dimension. I will upload a corrected part later tonight. i apologize for the inconvenience. EDIT 9-14-15 Added missing and fixed idler bracket .stl fileDesigned in Solid Edge ST7