I am just considering designing and building a CNC router, partly due to having found this site, and partly because I found a load of THK linear bearings and two leadscrews in a scrapyard!
I have a question though: the leadscrews appear to be THK large lead double ball ground ballscrews, part number BLK2525-2.8, with a lead of 25mm, and are about 1300mm long. I am concerned that the lead is too high, and will be inaccurate and prone to being back driven. I am guessing that to some extent I can alleviate this by changing the current 18tooth pulleys such that I gear it down (about 2:1 looks feasible), and using a big stepper motor.
Does anyone have any opinion on this? Would I be better trying to sell/swap them for a lower lead type?
Any opinions/answers greatly appreciated!