My balls are grinding

[JRouche]

Nuts that is. Ball nuts. I am setting up my milling machine with ball screws and nuts.

I am using 3/4" ball screws with pre-loaded nuts. They are spotlessly clean and oiled.
My problems is they have a slight grinding feel to them as I turn the screw. The grinding is similar to the grinding feeling you get when you run the nuts upside down, with the ball return at the bottom. I have the return at the top as it should be.

I have set the preload below manufactures specs. and still get a grinding/stiff rotation between the nut and screw. They are brand new and I don't see any obvious flaws.

I know the question is real "open" but, do any of you have a suggestion to what I may be doing wrong?

The screw is not being loaded sideways, alignment is good. The roughness is being felt as I turn the screw by hand. There is a definite irregularity along the entire length of the screw, not just in one area.

Thanks ahead, JRouche

[Stanko]

You might not be doing anything wrong. I recently read that rolled ballsrew rod can sometimes feel a bit rough. Ground ballscrew is smooth. Ill have a look and see if I can find the reference

[JRouche]

Thank you sir. JRouche

[precisionworks]

You may want to try running the machine for a week or two. There's a good possibility that the harder balls will burnish the softer screw and smooth out the action.

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Barry Milton

[Michael Az]

While I have never had a machine with ball screws, I turned the crank on a knee mill at reliable tool once and it was very rough. It had ball screws.
Michael

[JRouche]

<font face="Verdana, Arial" size="2">Originally posted by precisionworks:
You may want to try running the machine for a week or two. There's a good possibility that the harder balls will burnish the softer screw and smooth out the action.

</font>

Yep, thats where my next steps were taking me. I may take even more pre-load out (not really much there right now) and run her. I just didnt want to drive down that road of no return before consulting with some other folks and get some fresh opinions. JRouche

Oh yeah, the screw actually looks very smooth, the balls look less precise.

[This message has been edited by JRouche (edited 05-07-2005).]

[Stanko]

Here is a link to a faq regarding this

http://www.homeshopcnc.com/page2.html

No he is not my friend uncle brother or anyone else I know, just found him on ebay.

[JRouche]

Thanks Stanko, that kinda sets my mind at ease. I completely tore the nuts down and scrubbed them really well just incase there was some manufacturing grit/swarf. I'm gonna reassemble later and see. Thanks again. These are the screws/nuts I have.JRouche

http://www.rockfordballscrew.com/pbschart.htm

[JRouche]

I put the ball nut together and reassembled the screw. By the way, this is for the Y axis on a mill conversion. After aligning everything and cinchin her down all is smooth. I can run it through the entire travel now without any binding or crunching.

I think it was a combination of grit or debris (very slight) and the support bearing at the end of the shaft binding.

This is gonna be one neat mill. With just a med. amount of preload the response appears real tight. Just for effect I indicated the face of the saddle while slightly moving the ball screw and it tracks very nicely. I wont be able to measure backlash until the electronics are in place but it will be tight.

Again thanks for the help. JRouche