The reason for the alternate size balls was explained in a prior backlash elimination thread for ball screws on the CNC Zone website. To save you the time and trouble of searching for it via the us of the handy, dandy search engine:
The balls were alternately loaded big, little, big, little INTENTIONALLY by the OEM. The small balls act as idlers as they'll tend to try to rotate in the opposite direction as you move the system.
By using all the same size balls, more friction can be encountered and/or the rolilng action can wipe the lube of the balls as they try to spin "against" each other. Premature wear can result.
If you're reloading to reduce backlash, you should only go up in size a few 0.0001" at a time. If you go too big too fast, you can jamb the balls while loading and even brinnell the raceways - NOT GOOD.
NOTE and Caveat: When the system was originally built, the OEM probably had balls in size increments of 0.001mm or so to choose from. You'll be hard pressed to find that level of ball increment in the aftermarket. THey then selectively fit the balls to custom tailor the stiffness and/or backlash.
Reload with care and caution. Your well intended efforts could create more harm than good if you get carried away with preloading the system.  |