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BugEyedValiant
02-19-2009, 11:28 AM
I have a Millennium 3200 that has quite a bit of backlash in the y screw and am looking for a replacement. I contacted 3s and got a price from them and am looking for another quote. Does anyone have an idea where to send me?Is there anyway I can pick up a new ballscrew and machine it to fit my machine? If so, does anyone have the dimensions for the screw?

Thanks

Brent

Michael M
02-20-2009, 02:59 PM
Brent, how much backlash?

IIRC there was about .0007" in both X and Y on my 325. I put new .125" balls in both (and it was a good opportunity to clean out the ball nut and all the chips lurking inside the knee/under the table) and the Y tightened up noticeably (about half as much) but the X is still about the same. That indicates to me that the X axis is the one that was getting the most use and had more wear.

http://www.practicalmachinist.com/vb/showthread.php?t=118363

Details the tips that I got and what I did to repack the screws.

I haven't checked to see if the bearings at the end of the screws are contributing to the backlash. It wouldn't surprise me if they might need some adjusting.

Anyway, depending on the amount of wear you have it appears that a lot can come from the balls, and they are dead cheap to replace. I'd give that a try first before you start spending big money, unless you are talking about a hi-time machine with .005" of slop.

cheers,
Michael

BugEyedValiant
02-20-2009, 11:30 PM
It has about .0051 in backlash. I am able to put an indicator in the spindle and push the table back and forth around .005. The screw is galled pretty bad so something more than ball replacent is required. The knee was full of a lot of nasty stuff and am wondering if an insufficient lube problem was in its past. The X axis is in pretty good shape so l am lucky that it can go without repair.

Michael M
02-20-2009, 11:42 PM
That does sound pretty much beat to death.

I didn't take any measurements of the screws on my machine but the person who advised me on it said it looked like many a Japanese ball screw and nut seen in machines that he's repaired.

You may have to pull it and then look at

http://nookindustries.com/ball/BallHome.cfm

Here's some photos I took of the Y axis screw in my machine.. Maybe they will give you a head start. I think the screw was in the 1.25-1.5" range, but that's just a hazy recollection.

cheers,
Michael