I found a site a few weeks ago with some anti-backlash leadscrew nuts, the type with the spring around the outside, but alas, I cannot remember the name of the site and cannot find any anti-backlash nuts on the net. I'm currently waying up the pro's and con's (read price) between ballscrews and leadscrews, so if anyone knows where to get some decent acme nuts could they let me know please!