Dismantling a China C5 Ballscrew and giving it a C7

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13 Apr 2019 11:25 #130764 by pl7i92
I did face the problem on changing the Nut Direction on a China C5 SUF2005

as i needed the 8mm of extra space for the Toolchanger

so i did what all people say don't DO THIS avoid under any surcomstances

As well as they where sealed without screws !
and the seals where so tight to not fitting the loosen PIPE 15.25inside and 18mm outside into it to keep balls inside

THEN I gone the HARD way take a CAN(empty) and screw it out over the CAN let the BALLS faling out HEARTBEAT Moment

"ONLY" 30 balls cam out and they where in the roundtrip nut only in the first and last turn
THE Ballscrew nut hat the 3 inlays for 3 Round trip loops but no balls in there
the mesurment of all bals came up to 3.12-3,16 mm
Where 1/8" is 3.175
The Shop DIN Suply and Tusnelda Bianca Z├╝ndorf got 50 StealBalls for 2Euros

Now the Assamply to a C7 folowing this video

68Balls now in
The seal where now without function only to keep dirt away while in C5 mode they where
and finally it did Run more Smooth much faster and more precise i feel

it is realy a challenge and work but the aftermath is given me that match Benefit as i will do all other Ballscews as well

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13 Apr 2019 14:50 #130773 by OT-CNC
Re-balling will not increase the accuracy of your ball screw. What you are suggesting is to reduce the backlash. Your lead accuracy will remain.
You probably want to remove the seals before inserting the ball retaining tube or risk the chance of losing some balls when threading the screw out. (The red tube shown in that video towards the end) That tube is key item for anyone trying to do this for the 1st time. During assembly I found it's pretty likely to dislodge a ball. Tube helps keeping them in place.
Sometimes you can stand the screw and nut up vertically and fill the ball race while rotating.

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14 Apr 2019 00:25 #130805 by tommylight
Ohhhhh i have done that many times, to the point that it takes me about 3 minutes to have it done, but those where NSK 2505 and 4010 ! Have to do another one, chinese 2505 and it has much smaller balls than the NSK.

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14 Apr 2019 08:47 #130837 by pl7i92
Thanks for the advice

@ tom
balls are available in standard sizes all over
but they are not what the china guys use
seams that they sell only the fit as C5 C7 displace what is inside
meaning the Roller puts out lets say 200m per Set of roles
50meter C7 and 120m C5 the rest is not sold its for CNC production ready made mashines
as you can buy a 6040 asamplyes in CN for less then 400USD

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14 Apr 2019 12:18 #130845 by Leon82
The screw tolerance is error over 300 mm or 12 inch.

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15 Apr 2019 06:42 #130891 by pl7i92
i simply cand belive that 30 balls over less then 2 turns make the same as
68bals over 3full turns
as well as there where undersised
the 3,175 3.16-3,17 mutch more precise new balls

if you tell me thats the case i will test this on 3mm precice balls so more airspace better run

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15 Apr 2019 13:34 #130903 by Todd Zuercher
In a ball screw it is very normal to have half under-sized balls. The small balls work as spacers between the larger loaded ones doing the work, serving the same purpose as the bearing cage in an ordinary bearing.

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