On Mon, May 21, 2018 at 1:29 AM, Chris Albertson <albertson.ch...@gmail.com> wrote:
> Go to eBay and search for "SFU1605" That is a 16mm diameter by 5mm pitch > screw. These come with nuts that had best NEVER be removed I disagree! The nuts must ALWAYS be removed! :) In my experience all the the cheap ball screws are fitted with stock nuts like this: https://www.ebay.com/itm/272631911182 The nuts are not fitted to the individual screw as is done with higher end ball screws, so you will not loose any accuracy by removing/reinstalling the nut I have learned that while the screws are generally quite nice quality, around 15% of the nuts have incompletely ground races. The problem is that this is almost impossible to detect without taking the nut off the screw, since there are usually one or two fully ground races so the nuts still rotates smoothly. The result is that the load is concentrated on jut a few balls, and this causes rolling fatigue and subsequent flaking of the screw and nut. Once flaking sets in, you get very rapid wear of the screw and nut and backlash increases significantly. Now, instead of replacing the nut, which is an off-the-shelf item and could have been done before the machine was in operation, the machine is down and you have to wait for a screw to be machined and sent out! 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. Clean everything up well to get all that Chinese sand out and use a little Vaseline to hold the balls in place as you pack. On something small like your 16mm nut, use a toothpick with a little Vaseline to pick up and place the ball(s). With practice you can pick up and place 2-3 at a time. Just drag the toothpick out of the nut and the ball will stay. 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. When I did not have a lathe at hand, I have wrapped masking tape around a bic pen until it was the correct diameter. The layers of masking tape made kinda a padded surface, and in some ways it worked better than my plastic mandrels. The above goes for the "anti-backlash" preloaded nut pairs. Pack individually and then add shims between the nuts to set the preload. 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. If you have multiple screws/nuts, you can mix and match them to find the pairs that fit the best. Also, if you have a screw/nut that is oversized, it is fairly easy to get oversized balls to take up the slack. Sorry for writing a volume! Cheers, Kurt ------------------------------------------------------------------------------ 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
