The X-axis screw is the least smooth of the two that I purchased used. It is a manufactured by a Korean company called Mirae. Technical details from their site were next to non-existent. There was just enough information to determine whether the part was suitable for the task - i.e. that it was pre-loaded and had C5 accuracy. There are no obvious signs of wear to my untrained eye when I examined the groove with a loupe, so my suspicion falls on the balls - which get the most wear. Replacing them seems to be one of those voodoo tasks with some folks insisting that it can only be done by the manufacturer, and others saying "heck, I've done hundreds..." I think I will wait to see how the axis does once it is in place before I embark on this particular tasks. So, for future reference:
Good threads on the subject on Practical Machinist:
http://www.practicalmachinist.com/vb/general/advice-sought-ballscrew-replacement-ball-size-184584/
http://www.cnczone.com/forums/general_metal_working_machines/7416-re-loading_ballscrews.html
http://www.practicalmachinist.com/vb/general/ball-screw-installation-question-141922/
http://www.practicalmachinist.com/vb/general/how-get-balls-back-ballscrew-nut-214577/
The gist:
- There may be two sizes of balls in the tracks. One that contacts the groove followed by a spacer ball to keep the driven ones apart. Diameter difference is ~5 microns.
-
- Replacing the existing ones with (ever-so) slightly larger balls may deal with (some) backlash due to wear, but sounds to me like a poor idea as wear on the screw is likely to be in the middle, not evenly distributed over the length.
- When reloading, keep the balls out of the "no-ball" zone between the circuits.
- For ball-nuts with external returns such as mine, use the little red straw that comes with cans of WD40 to tamp the balls down into the circuit - pity I've lost all of mine!
- Work over a (clean!!) tray to catch any balls you may drop. Ummm, well yes.
- Have the patience of a saint.
This screw is metric so McMaster is a no-go for getting the balls.
The best source seems to be:
http://www.precisionballs.com/inventory/August/Ball_0001_mm.htm
Good threads on the subject on Practical Machinist:
http://www.practicalmachinist.com/vb/general/advice-sought-ballscrew-replacement-ball-size-184584/
http://www.cnczone.com/forums/general_metal_working_machines/7416-re-loading_ballscrews.html
http://www.practicalmachinist.com/vb/general/ball-screw-installation-question-141922/
http://www.practicalmachinist.com/vb/general/how-get-balls-back-ballscrew-nut-214577/
The gist:
- There may be two sizes of balls in the tracks. One that contacts the groove followed by a spacer ball to keep the driven ones apart. Diameter difference is ~5 microns.
-
- Replacing the existing ones with (ever-so) slightly larger balls may deal with (some) backlash due to wear, but sounds to me like a poor idea as wear on the screw is likely to be in the middle, not evenly distributed over the length.
- When reloading, keep the balls out of the "no-ball" zone between the circuits.
- For ball-nuts with external returns such as mine, use the little red straw that comes with cans of WD40 to tamp the balls down into the circuit - pity I've lost all of mine!
- Work over a (clean!!) tray to catch any balls you may drop. Ummm, well yes.
- Have the patience of a saint.
This screw is metric so McMaster is a no-go for getting the balls.
The best source seems to be:
http://www.precisionballs.com/inventory/August/Ball_0001_mm.htm
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