On Sunday 13 September 2020 21:28:48 Gregg Eshelman via Emc-users wrote: > There are companies that regrind worn ball screws then stuff them with > oversized balls, at much lower cost than a whole new ballscrew. ISTR > reading some claims of making a rolled screw as precise as a new > ground one since they're precision grinding the old rolled surface. > Whether or not it's cost effective to have a screw rebuilt would > depend on how easy or not it is to install a new one. If your machine > has something crazy custom then a regrind could be best.
I think one might say its custom. No end machining, so I cut to length, then bored a piece of A2 for a slip fit, put a slow tapered 50 tpi thread on the OD by cheating on g76, made nuts to fit the taper, then edm'd 4 slots .030 wide to the bottom of the hole, wet the screw with green loctite, pushed it into the bore and brought the nuts up to about 1/8 turn from broke, so effectively the rear of the shaft the motor turns becomes the screw. There's also a couple torrington cartridges around the shaft and miniature roller thrust washers countersunk into both front and rear faces of the original crank boss, without enough clearance to ever allow swarf to penetrate. The top and bottom of the channel the screw occupy's has been sealed up, so the screw itself is running in a sealed clean environment. My 25mm Z screw is fitted with a covering bellows on both sides of the carriage ball nut so it has a clean environment too. It has factory wiper felts in the nut that I grease about annually, and this custom x screw has wipers on both ends of the nut that I made froman old felt hat. The anchoring bolt for the nut cage can be removed and a cc or so on vactra 68 poured into the nut cage, which is sealed on the bottom. I intended it to outlast me. > Regrinding > would also be best if the screw is worn a lot more in one area. > Oversized balls that take up nearly all the lash in the less worn > areas will still leave the most worn spot loose. > This is true, but there wasn't much mileage on these screws so the thou oversize worked well. Have you a URL for one of these re-grinders? > On Sunday, September 13, 2020, 3:34:26 PM MDT, Gene Heskett > <[email protected]> wrote: > > On Sunday 13 September 2020 15:18:57 andy pugh wrote: > > On Sun, 13 Sep 2020 at 17:29, Gene Heskett <[email protected]> > > wrote: > > > Worse yet, if that screw does get damaged, I have no clue where to > > > source another like it. That small has never shown up on fleabay. > > > > https://www.automationshop.co.uk/mec > > No, they don't. 1 16mm, the smaller ones are all out of stock from > this side of the pond. These nuts have flanges that would preclude > using them in the available space. The ones I am using aren't > threaded or flanged, so I had to make cages to fit them. They are > 19mm in diameter plus return tubes. Looks like warmed over hell, but > the backlash is about a thou. > > > Or, second-hand from Korea: https://www.ebay.com/itm/193192165382 > > At least they are honest, all worn out, the precise is used up. > These were worn some but I found a bag of oversized balls ,0635 in > diameter, .001" oversized, and re-stuffing them was a bit tedious but > I did get it done. Took nearly all the backlash out of them. 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) If we desire respect for the law, we must first make the law respectable. - Louis D. Brandeis Genes Web page <http://geneslinuxbox.net:6309/gene> _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
