[vroemm]

Just a though of a inexperienced hobby CNC router builder.

If you use one bronze nut on the thread axis, the bronze nut will start wearing out.
When the space becomes 0.2 mm you might want to replace the bronze nut.
Cost money :-)

Here it might be better and cheaper to use two bronze nuts instead of one.

http://home.wanadoo.nl/vroemm/cnc/two-bronze-nuts/

Turn the nuts to make them press together lightly.

When it starts wearing out, you can turn the nuts again, with this removing the space created by wearing out.

When you want to do a extra accurate job with your cnc router, you can adjust the nut before you begin.
No need to wonder if you are going to spend the money of buying a new nut, just for this one extra accurate job.

You can keep repeating this until the thread in one of the nuts is completely gone.

At first it is more expensive because you have to buy 2 nuts to start with.
At the long term it becomes cheaper because you can use the nuts much longer.

In the picture above you see two nuts which a worn out a lot.
In this way the nuts are still usable.

[lakeside]

with two nuts would you not incrase load on thread and have a binding issue?

[lakeside]

Also you would need to have the exact same starting point on thread of nut or you would lock up would you not?

[RICHARD ZASTROW]

Sometimes the nuts are spring loaded with just enough pressure to avoid binding but enough pressure to avoid losing position. These are commercially available in bronze and teflon type materials. Usually they are small diameter. Split nuts of various types were often used in the more preciseACME screw applications and worm/worm wheel installations.

[paulC]

There are all sorts of variations of this concept. The thing that is needed is a means of locking the nuts in place without loading the thread excessively. These methods include springs, blocks with grub screws, o rings and other ideas. All have pros and cons. Keep working on your idea. Will be interested to see if you can come up with something simple and inovative.
Paul

[lakeside]

after thinking about this and reading the answer you got I have see this type of set up on a lead screw before it was spring loaded but any thing can be made better so keep going and keep us informed best of luck to you with this project

[vroemm]

The thing that is needed is a means of locking the nuts in place without loading the thread excessively.

Yep.

I am in a early stage of theoretically thinking about it. :-)
When starting to make it for real lots of problems will appear, no doubt about it :-)
And i have a lot other things to do before i start making it for real.

I was thinking of making a lever on one nut.
Suppose you have a lead screw which moves 3 mm for each rotation.
Make a lever on it of 100 mm.
With a 1 mm scale on the end.
Then 1 mm of movement on the end of the level will result in +/- 0.005 mm of movement on the lead screw.
Then bolt the lever to a secure part.
Then see how much current the servo motor draws, the more current the heavier the friction of the nuts on the lead screw.
If to much current, adjust the level setting.

Could this work in real life ?
Or am i missing to much ? :-)

Interesting problem, but i have so much to do before i get to it.

[vroemm]

Hi..

I came up with a easy way to make and use it.
I have not tried it.
Would this work ?
Or are there problems ?



On this link you can find the DXF drawing file.
http://home.wanadoo.nl/vroemm/cnc/two-bronze-nuts/

If one turn of the screw gives 3 mm travel.
Then one degree of turning the green nut will give 3/360= 0.00833 mm play reduction.
This is nicely accurate :-)

Well what do you think about this method ?
Where are the pitfalls ?
Is this useful for hobbyists ?

Vroemm

[jerber]

I think it will work.

I made my nuts with the same principle.
The only thing difference is that I use a spring between the two nuts.
One nut is fixed the other one floats.



I just have to losen the six bolts and tighten them again to eliminate play.

[Geof]

Hi..

I came up with a easy way to make and use it.
I have not tried it.
Would this work ?
Vroemm

It will probably work, I have a manual mill with backlash adjustment on the X axis nut that is very similar to your design.

[svenakela]

There are hundreds of members here using the same setup. For example, check the DIY and desktop forums. Search and thee shall find...

[snoopy27]

Yep.

I am in a early stage of theoretically thinking about it. :-)
When starting to make it for real lots of problems will appear, no doubt about it :-)
And i have a lot other things to do before i start making it for real.

I was thinking of making a lever on one nut.
Suppose you have a lead screw which moves 3 mm for each rotation.
Make a lever on it of 100 mm.
With a 1 mm scale on the end.
Then 1 mm of movement on the end of the level will result in +/- 0.005 mm of movement on the lead screw.
Then bolt the lever to a secure part.
Then see how much current the servo motor draws, the more current the heavier the friction of the nuts on the lead screw.
If to much current, adjust the level setting.

Could this work in real life ?
Or am i missing to much ? :-)

Interesting problem, but i have so much to do before i get to it.

This looks interestring. Mechanical design isn't my area of expertise, but I was wondering what about slipting a nut or placing a wave washer between two nuts that wouldn't put to much preload on the nuts. My question here is side loading and linear alignment. Too much side load of a split nut or double nut can also cause problems I would think. I know I am really suggesting nothing new, but this seems simplier and would require no manual adjustment until one had to relace the nut.

[vroemm]

This looks interestring. Mechanical design isn't my area of expertise, but I was wondering what about slipting a nut or placing a wave washer between two nuts that wouldn't put to much preload on the nuts. My question here is side loading and linear alignment. Too much side load of a split nut or double nut can also cause problems I would think. I know I am really suggesting nothing new, but this seems simplier and would require no manual adjustment until one had to relace the nut.

I am not sure i understand what you mean.
Could you clarify or rephrase it ?

[chinsettawong]

This is how I made mine.




I simply milled the two pieces of plastic with a hexagon hole in the middle. Then I pressed in the female nuts. They work out quite well.