On Mon, 2008-08-18 at 23:23 -0700, An Pham Duc wrote: > I am finding some lead screw for my mini CNC. Please tell me what kind > of lead screw I should use > Thank you
With a manual machine, which usually has leadscrews, a bit of clearance is needed between the nut and threads to keep friction and wear down. With this clearance, the machinist needs to have a technique that compensates for this clearance by always coming to a dimension from the same direction and if necessary locking the non moving axes while cutting. For CNC, these techniques are not available, so you need to have a low friction, zero clearance ball screw as well as zero clearance ball bearings to mount the ends of the ballscrews. For zero clearance, the nuts and end bearings need to be preloaded some way. For nuts, I believe the best way is with two ball nuts with adjustable clearance between them. Some single ballnuts can be preloaded with slightly over-sized balls which may need to be changed as the screw wears. There is a choice between ground and rolled ballscrews. The ground ballscrews are generally more accurate and last longer under heavier loads, but are considerably more expensive. What will work for your application, will depend on the details of your machine, what you want to do with it, and your budget. -- Kirk Wallace (California, USA http://www.wallacecompany.com/machine_shop/ Hardinge HNC/EMC CNC lathe, Bridgeport mill conversion, doing XY now, Zubal lathe conversion pending Craftsman AA 109 restoration Shizuoka ST-N/EMC CNC) ------------------------------------------------------------------------- This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK & win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100&url=/ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
