[letmefixit]

Hi everyone. I was thinking of trying something with my ball nuts. The idea was to have the two ball nuts opposing each other on the support. See the attached crude drawing. The theroy that i had was to be able to screw the ball nuts into the support on each side untill the backlash was gone out of the screw then tightening set screws down on the threads of the ball nuts to lock them in place. What do you think. Will it work. Or am i going to be doing alot of adjusting?

dj

[michaelthomas]

It probably won't work the way you might hope. The second nut needs to float to accommodate for the screw inaccuracies, yet still maintain preload. You may be able to reduce the backlash, but it won't get you near zero without binding and causing fast wear.

[jetflatline]

Not sure if this helps, but the ones I received from IH have the tensioner in the middle, it pushes them apart. So you get it as snug as you can while you're spinning them onto the rod then twist this tensioner ring and it shoves them a tiny bit apart, but there's still a wee bit of play in them.

[instructor37]

Hi everyone. I was thinking of trying something with my ball nuts. The idea was to have the two ball nuts opposing each other on the support. See the attached crude drawing. The theroy that i had was to be able to screw the ball nuts into the support on each side untill the backlash was gone out of the screw then tightening set screws down on the threads of the ball nuts to lock them in place. What do you think. Will it work. Or am i going to be doing alot of adjusting?

dj

Never tried it, but if the pitch of the mounting threads on your nut are different than the pitch of the ball screw, then as you try to turn the nut to reduce the lash it will be binding against the screw.

[arizonavideo]

You need to think about the fact that you have two different thread pitches so you cant thread the nuts together like that. It just wont work unless you pack the ball nuts in one nut after you mount them in the mount which is not that bad of a idea.

[letmefixit]

Thanks for all the input. I have had it together on a test piece of ball screw. it is very finiky to get it to run smoothly and not feel any lash. guess i need to figure out a differnt way to do this with the ball nuts i have. They are not thread on both ends so i cant screw one into the other with a spring washer inbetween. Any Ideas???

dj

[michaelthomas]

There are lots of ways to do it......most, if not all, are more complicated than this. It's just a stack of wave washers (11 of them) between two ballnuts. It puts about 80 lbs of preload in the system. Only one nut is solidly fixed to the mount when used....the other just floats to absorb the inconsistencies. Depending on where its mounted, you may need to fabricate something to hold the slave ballnut in line with the master (fixed) so it cannot rotate.

If you screw one ballnut to another solidly, you will be in the same boat you're in now. One has to float.

In my example, the spring washers allow the second nut to move while maintaining a preload. The washers can be compressed about .020 further than their static position......which is plenty of forgive.

[jetflatline]

stupid question time: Why not just buy a double ballnut that has a tensioner?

[michaelthomas]

It's a combination of reasons for me. The roton nuts I'm using will fit much easier in the place that I want them to go because the 5/8 nuts are 1" square and do not have a flange.

The price for these are 26.00 each......so I have about 55.00 in one unit including springs. Similar sized 1" square preloaded nuts are way more expensive.

Roton sells double nuts.....but they are just double the load rating, they are not preloaded. Backlash will still be similar to the singles.

Linearmotionbearings2006 on ebay sells some C7 ballscrews and nuts very cheap. These are preloaded with a flange. C7 are a better grade than the rotons.

[letmefixit]

Well my reasoning was... I thought I had a better Idea, and was much cheaper. But all is good. I was able to get with my local bearing distributor who also is a Roton Distributor. I got all the fittings and spring washers to make my 3/4" ball nuts preloaded. $120 bucks more. I think i will survive now. This has be a heck of a learning experience. I'm learning lots. Great input from the group. Most the time they teach ya with out making you look like total idiot. Hope to be mounting some hardware on my mill next week.

DJ