I agree: > It is not a quarter as hard to repack a ball nut as a lot of people make it > out to be. > If you can repack the bearings on your bicycle, you will have no problem. > You can probably find good general instructions for repacking a ball nut in > the steering section of your autos service manual. > > If you are not careful the balls can get pushed out of place when putting > the nut back on the screw. > If this is a problem, you can turn a plastic mandrel with an OD just shy of > the Minor Diameter of the screw. > Insert this into the nut and use it to transfer the nut to the screw.
If you have to cut the screw to machine to length, the additional section of screw can be used to hold the balls in place. If both ends of screw and cut-off-screw-end are reasonably flat and square, rotating the cut off part lets you line up the tracks, and you can wind the screw out as the cut-off part is held against the end as though it was one continuous length, so you end up with the screw free, and the cut-off part inside the nut, acting as a mandrel. I can do that on two of my axes. The third requires a plain mandrel as Kurt suggests. > > Those cheap ball nuts are nothing to be afraid of. They are dead simple and > not much you can do wrong. > You will almost certainly find that you nuts run much more smoothly after > repacking them. > And for me at least, the peace of mind that comes from knowing the nuts are > good is well worth the 10 minutes it takes to check them. > > Also, if you have a screw/nut that is oversized, it is fairly easy to get > oversized balls to take up the slack. > When a ball nut has been in use for so long that the backlash has increased, oversize balls are one way of returning it to a more reasonable fit. My supplier holds large stocks of balls of different sizes fro that purpose. One other point: I use THK nuts which are like sections of rectangular bar. They have a flat bottom with 4 tapped holes for securing the nut to a flat surface (so the flange is effectively at right angles to the ones shown in most catalogues. Sadly, that means they are in short supply, and therefore not cheap. They are, however, very easy to fit on the saddle of a mill. I use a little platform with a turned spigot to fit the usual hole provided for a standard leadscrew nut, allowing some rotation for self-alignment. See: https://tech.thk.com/en/products/pdf/en_a15_282.pdf square nuts type BNT. Marcus ------------------------------------------------------------------------------ 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 [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
