Ballnuts

[M250cnc]

Fitting them on the ballscrew is a different story. When they screw on they seperate. What I had to do was tighten them together with some large grips and fiddle about with the keyways to get them together. Its a right PITA. They tighten up quite a bit when together and take more effort to move them along the screw but I suppose thats the price to pay for zero backlash.Ian

In my case when i used double nuts they were too slack, i looked around on the net and found that they should be sprung in the middle. So i modified two big belleville washers and they seem to work well

The thing I`m really not impressed with is the end seals. They are made from hard material like nylon and held in place with two pointed grub screws set 180 degrees apart. Its really crappy. I think a softer better fitting rubber material would do a far better job of sealing the bearings and sweeping the screw and would stay in place better. I will try to post a pic later to let you see what I mean.

Ian

Those seals are really only good for keeping out crud while they are being built into the machine, what you really should be using is sprung ball screw covers, if you fail to do this then they are gonna wear/bind sooner rather than later.

Phil

[Robin Hewitt]

Another vote for springs, I preload to 1/4 ton and they are really smooth with truly zero backlash. The spacer shim gives low backlash not zero, it can't compensate when they bed in. It shouldn't be hard to reassemble the nut though, is there any possibility you muddled the spacers up?

[Jonathan]

Another vote for springs, I preload to 1/4 ton and they are really smooth with truly zero backlash.

How much less smooth are they than a single ballnut? I'm thinking of doing this with the spinning nut idea on the router.

[Robin Hewitt]

If you spring the nuts it should be perfectly smooth, it can ride over imperfections without cogging. PITA to do but you get your reward when you put the DTI on it :tup: