[rholliday]

Roton has good prices on ball screws but Roton doesn't show any data on backlash.

[Bubba]

IF I remember correctly, a standard nut will have .003 to .006" of backlash. At least that is what I was told when I asked before buying mine several years ago. I used a double nut spring loaded setup for zero backlash.

[RicknBeachcrest]

Hi Bubba,
Any chance of getting a couple of pictures of your set up to get a zero backlash setup using Roton? I am getting real close to having to order a ball screw and thread. Roton has great prices and it would be great to be able to get a zero backlash setup.

Also did you use the Roton flange or something else?

Thanks for any insight you can provide.

Rick

[rholliday]

Hi Rick and Bubba
I received my ball screw and ball nuts Saturday. They have a $60 min so I ordered 2 nuts and 2 ft of the screw 5/8 .2 in lead. I am redoing my quill drive on a sharp knee mill that I converted to CNC in 09. By cutting off some boses on the front of the quill head I now have room to add the second ball nut.
I will be making my own flange.


thanks for the reply.
Robert in Phoenix AZ
If we are older than dirt that must make us dirty old men.

[michaelthomas]

This is what I did with mine. I don't think their is a simpler setup. It's just a stack of wavy washers that are compressed between the nuts. The way it is now gives me about 80 lbs of pressure. I don't have it on a machine yet, so I don't really know if that is enough. It is zero backlash, though.....or at least for the measuring equipment that I own.

If its not enough, I'll have to make a spacer that takes up the appropriate amount of space after adding more washers to align the nuts again.....or add enough washers to make the nut compress them at one more full turn (.200").

I'm just going to use a piece of U shaped channel for the nuts to ride in that will not let them turn in respect to each other, but will still allow the second nut to float and absorb the inconsistencies. The washers' outside diameter is the same as the ball nuts, so the channel should keep them from getting off center.

[Bubba]

As shown on my old web page, here are the components.

My CNC Homepage

I have a "socket" that fits over the back end of the fixed nut and then the washers go between that and the collar on the second nut which is then pinned to the socket by means of a 6-32 screw. The collar also has a setscrew to maintain its location on the nut thread. As best I remember, the pre-load is on the order of 270#
HTH

[michaelthomas]

Hey Bubba.......what tension wavy washers do you have?

The highest I could find is 7lbs per washer.....and i believe I have 11 in my preload pack.

I noticed you have 6, so they must be much higher tension to get 280#.

I like your seal idea.

[Bubba]

OOPS, your right. I don't have that much tension. The washers I used are 9715K89
from Mcmaster and are rated at 14# and I just found the spreadsheet where I calculated the load using 6 washers and it is 84# with a compression of .067". Been a long time since I did this so had a senior moment. The more I think about it, that is the max that Thompson recommends on their system??
Thats what I get for relying strictly on memory:{(