Greetings guys; That <$200 2505 by 1475 screw I used for z drive is haunting me, again.
First, I never did get around to shimming some preload into the thrust bearing, so a years messing around later, the far end of the screw is moving around .0055" as it takes up the reversal slack. And obviously the balls in the ballnut need refilled with decent balls about .005" bigger. Then today I made a cutting tool, .0495" wide, to cut those 10 tpi square threads I'll need on the end of this barrel, and I am damned glad I picked up a piece of pvc pipe to practice on. Setting g76 with a q0.000, I found it was drifting left approximately .001" per cycle, and that a q-0.5 helped but something wasn't slipping uniformly, so I added a microsecond to the driver pulses, no diff, then started on the mechanicals, so the first 5 or so passes did not result in a usable thread. I wound up snugging up the setscrews in the motor pulley, and in the pulley driving the screw before that seemed to settle. The backlash seems to vary at random by about 2 thou, so the starting point of each sweep to the left at cutting depth wanders around about 2 thou. I can, its a pita to do, reynolds wrap the thrust bearings to get a bit of preload, which would cut the backlash in half, but where the heck do I find oversized balls for the nut that are that grossly oversized? AFAIK, its a std Chinese 2505 ball and screw, but I don't have a clue how big the std balls for one of those critters are. Has anyone here tried to rebuild one of these, or are those rolled screws and its equally cheap nut so soft I'd be wasting my time? Thanks all. Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) Genes Web page <http://geneslinuxbox.net:6309/gene> ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
