[signIT]

Hi,

I have done a simple sketch of an anti backlash nut (not to scale) the idea is to use some type of rubber or suitable material to act as a spring.
This construction may be easy to make to anyone as it only needs a simple lathe and other common tools.

Leffe

[signIT]

Another sketch of my idea showing threaded holes for mounting bracket!

Leffe

[signIT]

Or a belleville spring loaded force se attachment

Leffe

[rceebuilder]

I don't understand what for is the rubber part . I think You must keep one nut free and the other is fixed to table or whatever. Thus the rubber can push the free nut to fill the thread gap.
Murat..

[jans123]

It exist many ways to pre-load the nut and I have used a few of them. One drawback is that it always add load to the nut/screw contact and it increases the load in the direction the nut is moving as it has to take both the load and the preload on that direction. You will in other words get an increase in wear on nut and screw. The positiv thing is is that the slack is similair to a pre- loaded ballscrew (but you will have a hogher wear) in other words zero as long as the load doesn't exceed the preload on the "lose" direction. You can also pre-load the bearings in one end of the screw in a similair way with rubber or spring as force inducing element. But, and that is important, look at your drawings once more and read Mr rceebuilder's comment. I think he wants to give you a hint, but don't give up the entire idea.
/jan

[signIT]

rceebuilder,

My intention with this sketch is, it would be nice to get some ideas on how to make it better or if it better to skip it.
The rubber or other suitable material between the two Delrin parts would act as a spring, in my first sketch the two parts is not bound together and therefore one part can be attached to the gantry drive and the other should be free to move towards the mounting plate showed in the last sketch.

So... if this is a bad or good idea I just don't know, maybe I will try to build it, but before I begin it would be nice if any could give me a hint.

Leffe

[signIT]

Hi,

Another idea, now with a free Delrin part but now it is connected to the fixed part with a hard rubber tube wich are attached to the Delrin parts by spring clamps, it should work rather well, one of the main reason with this design idea is it must be cheap,reliable and easy to repair.

I think this design also make it easy to trim the backlash, maybe the hard rubber tube can be replaced by an sturdy metal spring place in the same position as the rubber tube but it would be a bit hard to mount it in to the Delrin parts.

Leffe

[rippersoft]

How about a short length of garden hose, or other flexible hose that fits over the metal nuts which are threaded for the leadscrew and held in place with hose clamps. The hose can have a short length of tubing inside, between the nuts, so that there is something solid to clamp.

The hose will twist a little and prevent binding. I use this setup on X, Y, and Z of my machine with 3/8 x 16 UNC rod and nuts. Lube it well and it works good. Very cheap. Original idea was seen on a French site for foam cutters and used surgical tubing.

[dertsap]

i like your idea of using a spring between the nuts , but delrin isn t going to wear nice at all , the nuts will get sticky with wear , have you considered steel nuts , less wear and less friction , if you use a cast iron nut on a harder steel rod , you will get a self lubing effect between the two steels , lots of screw jacks were built under that principal

[chuckknigh]

I'll never understand why people insist on overengineering these things. Remember KISS when designing, people.

The goal is to apply a preload to the double nut, so that it eliminates backlash. This can be as simple as a compressible spacer (rubber washer) or a spring. A viable alternative is to slightly bind the nuts, which will have the same effect.

I used the following design for my router, and it worked great. Plastic nuts have EXTREMELY little backlash to start with, and this design can easily be adjusted for wear. The slot can be compressed to "bind" the nuts slightly, which eliminates backlash.

-- Chuck Knight

[dertsap]

i have to agree with you chuck , i don t have any anti backlash nuts yet , but i m still interpolating in aluminum and holding a roundness within .001 , a few thou of backlash can be solved by setting the software , 0 backlash on any screw that is not precision ground will have some tight spots , in my experience anyhow , my motors don t have enough power to warrent the added friction , i have to sometimes remind myself there is a difference between machinist tolerances and carpenters tolerances in the work piece

[signIT]

Yeah! KISS is the word but I had some bad results from a couple of KISS constructions, my idea was to find a simple way to make a AB nut.
In #7 the rubber is glued to the two acme nuts the two nuts was first tensioned to each other and then I let the glue set.

It is much easier to use a rubber bracket as spring load because of the glueing idea.

[korntheuer]

Chuck,

You image of your AB nut did not come through. I checked your site
http://chuckknight.bravehost.com/router/router.html and it has the
same problem. I would like to see the details of this idea. Can you give
a link to where you found this idea on the net?

Thanks

[ger21]

I made mine like the ones at the bottom of this page. Just put an O-ring on the end to keep it tight.
http://www.cnconabudget.com/stuff.html

[jsnickel]

Do you have a sketck for these homemade AB nuts? I have the equipment to machine some for my cnc mill in progress.