[ezland00]

Hello all, I need some advise on how to mount the anti-backlash nuts. Below is a picture of my ½-10 leadscrew and the nut screw.

[balsaman]

looks like a regular nut.

options:

a) weld it to a washer and drill the washer for tiny bolts.

b) drill a washer for tiny bolts and sandwitch the nut between the axis and the washer.

Eric

[kong]

Expanding on balsmans idea, get two nuts for each axis, drill both for a bolt, and tap one for the bolt's thread. You can add shims in between to create the anti-backlash effect as they are bolted together.

[creative_mind]

How about a picture or a drawing?

[kong]

A picture of......the mounting? Well the mounting will depend on the design of the router. My own nuts are mounted with holes drilled thorugh the side, then bolted onto a rail which is perpendicular to the axis of travel:

edit - OMG! I just re-read Balsamans post, and it seems I'm way off topic, please excuse me!

[ezland00]

Can you please draw a picture for me so i can understand. Thanks

[chuckknigh]

The first question we should ask is: Is this an antibacklash nut? I don't see any means of adjustment, in your picture...how do you adjust the nut to "dial out" the backlash?

Assuming it is an antibacklash nut, there are a LOT of possibilities for mounting it. One would be to attach (weld, braze, solder, JB-Weld epoxy) a washer to the nut. You could drill holes through the washer, and "nail it" onto the sliding part of your axis.

Another would be to drill an appropriately sized/shaped hole, and simply insert the nut into the hole. Use a set screw to firmly attach it in place.

Now, assuming it's not an antibacklash nut, you need some way to get rid of the backlash. Rather than type the equivalent to CNC101 in this message, just let us know if this is the case. We can make suggestions, if they're needed.

Bottom line, this is how they work: One side of the nut "pushes" against one side of the threads, and the other side of the nut pushes against the other side of the threads. That way there is no play, at all. This is done with a 2 part nut, usually, and some way to vary the distance between them. another way is to "squeeze/deform" the nut, giving the same effect.

-- Chuck Knight

[Mr.Chips]

Here is a method for managing backlash, it was posted by Balsaman.
"About anti backlash nuts. I saw on the net guys make a nut from brass, cut in half 90% of the way through with a hack saw, then drill and tap half the nut. Install a set screw, which is used to adjust out the backlash by splitting the nut against the rod.

Here is a picture:

Eric "

Hager

[Mr.Chips]

This backlash method was posted by Cranky

Hager
"Here is an antibacklash nut everybody can make. You start with a rod or bar of Delrin or Nylon. Tap a hole through the center. Slot the end once or twice. File in a groove around the slotted section. Put an O-ring over the slotted section in the groove. File a flat spot on the rod or use a side on the bar. Tap two holes for mounting. See Pic. A solid block of Delrin tapped has almost no backlash, but if you have to have an antibacklash nut here it is.

Cranky

crankorgan has attached this image (view full image):"

[fyffe555]

ezland00

As Balsaman said, What you have there is a regular 1/2-10 Acme nut. It's not antibacklash or adjustable.

The guys have given some good examples of mounting it, drill the face and bolt it to a plate with a 1/2" hole is my favorite, or tap one of the hex faces and use a bolt and lock nut. I wouldn't use any form of welding though because it might deform.

To make the examples of an adjustable nut like those suggested you'll need to get a 1/2-10 Acme Tap which are not cheap and I've found some varience between the tap and the screw that I bought. Like Balsaman I finally made a tap from an offcut of the screw itself with a grinder and it worked fine on Delrin.

Depending upon the quality of the screw and nut the actual backlash present may be as low as 3thou which might work fine for you, more likely the backlash will be higher. The precision reduces as the parts get cheaper.

If its a standard nut, and it looks like it. It's 5/8 wide, that is the threaded section is 5/8 long and so has about 6 1/4 turns in it. I think that's too few to try and modify the nut buy splitting and spreading because you'll have too few turns as a bearing surface. While it might work there are wear issues and looking at your picture it looks like std oil finish stuff which is not as wear resistant as some of the other stuff.

You can buy antibacklash nuts for 1/2-10 or make your own. It depends on what you're trying to cut. Low loads then plastic is fine. heavier stuff needs a more engineered solution..

good luck..

Andrew

[High Seas]

fyffe555

Andrew - Jim Here.
Like your idea re making a tap. Thats what I need to do at this point.
Been down the casting track and still a but unhappy with the results. Tapping Delrin may be my next effort.

So for your tap made from the Acme rod off-cut:
1. Did you taper it so it looks lke a tap?
2. Did you taper all the way to the smaller diameter of the threaded rod?
3. Did you "flute" it along the long axis as a clean out?
4. Any other tricks I should know about to make this tool?
Thanks
:cheers: Jim

[fyffe555]

Jim,

I blatantly copied a balsaman idea. Pretty much copied a pic of the one he did some time ago, think it was on the RCgroups thread.

I just made it look like a regular tap. I free handed a taper to below the small diameter, cut two slots for flutes with the angle grinder into the taper and a short length of full diameter to give a cutting edge. I fixed the piece in bearings to hold it and rotate it and clamped the dremel with a stone wheel in a three way machinists vice next to it as a bastard's lathe and cleaned it up. Last bit's not necessary if you're any good at freehanding which i'm not....

Found it to be more than adequate for Delrin and Aluminium if the pilot hole is sized right and cut using a drill press turning the bit by hand. You can adjust the tightness of the part if necessary by the depth of cut and the size of the pilot.

Tried casting with moglice (sp?) and it was ok but my leadscrew, although acme was the cheaper end and so not totally accurate over its length. Still ended up with a little backlash and inconsistent load over the range of motion.

Using a plastic as suggested by many others before me that's not a problem, unless you're trying to cut steel or something. Making sure there's at least 10 turns in the nut and starting with a slightly undersized pilot I've found there's no need for any backlash mechanism, its close enough for me and it seems to be lasting fine.

hth,

Andrew

[kong]

Here's a pic that may help you High seas. The tap isn't too clear, but like fyffe555 said, tapered and then I cut about 8 flutes with a hacksaw/file. You can also see the two-part anti backlash nuts I made, but not sure if they would be possible without the use of a lathe. I think the pilot hole is Thread OD - Thread pitch.

[pminmo]

Kong those nuts look great what is the black material?

[Wjman]

Good job I read the earlier replies otherwise
"Kong those nuts look great what is the black material" could have been taken in another context. LOL.
Mark...

[kong]

Originally posted by pminmo
Kong those nuts look great what is the black material?

They are made from Delrin (acetal).

[High Seas]

That tap looks real professional and the nuts too!
We're building a tap today and will cut some nuts! Gonna use another plastic material - similar to Delrin/acetal - got it on hand. Tried using the rod off-cut and result was not satisfactory - but now have the clue!
Thanks Heaps!
:cheers: Jim

[ezland00]

Originally posted by High Seas
That tap looks real professional and the nuts too!
We're building a tap today and will cut some nuts! Gonna use another plastic material - similar to Delrin/acetal - got it on hand. Tried using the rod off-cut and result was not satisfactory - but now have the clue!
Thanks Heaps!
:cheers: Jim

Post some pictures if you can.

thanks
EZ

[kong]

As requested by ezland via PM (just so you don't think I'm going loopy), you can download a plan of the nut HERE
The only thing I left out were the two grub screws used to secure the top nut section in position. It is an Autocad 2000 format DXF, and units should be set to metric (mm). If it doesn't work, let me know.
And here's the piccy.

[ezland00]

Is there any demo version of Autocad 2000 that i can use to open the file? Please post the link if there is any.