Ballscrew Nut Replacement Parts

10 Sep 2019 13:24 #144695 by pl7i92
we are very lucky in germany /europ as we got
called "tusnelda " the Shop of bearing Wonder in berlin
if the link only gets to main indey see sidelist "KUGELN"
all kind of Balls all mesurments and a price of no extra

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11 Sep 2019 01:17 #144768 by andypugh

Checked all the balls under a 200x microscope.
Half the balls are worn, but probably re-usable.

It's not unusual for half the balls to be a smaller size, and they act only as spacers.

I bought a set of oversize balls from Amazon a few years ago. But I don't seem to be able to find the vendor now.
(They were "Toolsupply" on eBay and Amazon.)

This is one option:

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13 Sep 2019 12:13 #145052 by electrosteam
Got some 1/4" balls from a local bearing supplier.
The originals were 103 x 6.365 mm
Did some trial ball loads and mount to screw, it is amazing what some simple jigging can do.

The 108 x 1/4" balls are definitely loose.
Nut drops under gravity the full length of the screw.

The 6.365 mm plus 1/4" to make up to 108 seem reasonable, but I think still loose.
The nut does not drop the full length under gravity, but it does rotate many turns before stopping.

Now need to guess the correct size required and purchase (overseas for me).
Prices appear to be about USD 0.72 for 6.37 mm balls, so significant cost into Australia.

What allowance should I allow for lubricant and heat ?

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21 Oct 2019 21:12 #148494 by electrosteam
The rotation test above was repeated with ISO 68 as lubrication.
The nut would self-start and rotate to the bottom of the screw.

Much testing to confirm size at 6.365 mm.
I finally decided the DTI had an offset error, could be a worn test foot (concave).

The loaded ball screw was clamped by the nut horizontally and a DTI detecting height applied at the end.
Manual movement up/dn showed about 5 microns (mm) slack between screw and nut.

The loaded ballscrew was clamped with V-blocks to the mill table and a DTI applied to detect horizontal nut movement.
The nut was pushed/pulled manually and about 25 microns (mm) backlash detected.

Spent some time searching for guidance on the effects of a stated ball size increase to no avail.
When the time came to pay money, got cold feet on the size increase and ordered 6.3685 mm balls from Bal-tec in CA.

Loaded the nut with the new balls, lubricated with the shipment oil (very light).
The nut was reluctant to start self-rotation, but drops to the bottom if started.
Obviously I could have gone larger.

A repeat of the mill table test showed about 18 microns (mm) backlash.

I will call it quits and fit the ballscrew to the mill.

I am sure new adventures will eventuate.
Thanks for all the comments.

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