Part 24 of the Fadal VMC 4020 reconditioning series. In this video you will see how I repacked the ball nut of the X axis witch is done totally differently than with the Y axis ball nut.
If you do, take a micrometer and mesure a bunch of the balls. They should be 0.125 in. If they are smaller and especially if they varies in size like on my Y axis ball screw, I believe it’s a cheap but great upgrade to replace the balls with new ones. Let me know how it goes if you do!
@@BlaiseBarrette The way these screws may have been originally packed is with alternating size balls. There would be larger balls to provide the main bearing surface and take up the backlash, and in between each of these is a slightly smaller ball that turns the opposite way and reduces the chance of rubbing friction between the balls. If you have two balls the same size touching and rolling on the track, they will rub against each other at a point because there is no bearing cage to keep them separated. The smaller balls act as a bearing cage and keep the balls from rubbing. That's how my ball screw was set up at least, the balls were two distinct sizes alternating in the nut.
Wow! This is very interesting! It makes so much sense to do it this way! In the case of my ball screws, I don’t think it was the case. For sure, the X axis ball screw, all the balls measured exactly 0.125 in on the micrometer. It could have been alternated like you described on the Y axis ball screw but It’s impossible to tell because the balls measured very in inconsistently. I plan on cleaning the Z axis ball screw soon so I’ll be sure to keep an eye out for that! Thanks!
