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View Full Version : how to Mount this anti-blacklash nut?



ezland00
11-05-2003, 08:57 PM
Hello all, I need some advise on how to mount the anti-backlash nuts. Below is a picture of my ˝-10 leadscrew and the nut screw.

balsaman
11-05-2003, 10:06 PM
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
11-06-2003, 09:50 AM
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
11-06-2003, 10:13 AM
How about a picture or a drawing? :confused:

kong
11-06-2003, 10:22 AM
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
11-06-2003, 09:56 PM
Can you please draw a picture for me so i can understand. Thanks

chuckknigh
11-06-2003, 10:43 PM
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
11-06-2003, 11:31 PM
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
11-06-2003, 11:33 PM
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
11-07-2003, 10:35 AM
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
11-07-2003, 05:06 PM
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
11-07-2003, 05:37 PM
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
11-08-2003, 08:31 AM
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
11-08-2003, 01:55 PM
Kong those nuts look great what is the black material?

Wjman
11-08-2003, 03:33 PM
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
11-08-2003, 04:07 PM
Originally posted by pminmo
Kong those nuts look great what is the black material?
They are made from Delrin (acetal).

High Seas
11-09-2003, 07:57 AM
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
11-09-2003, 11:57 AM
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
11-09-2003, 12:12 PM
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 (http://www.btinternet.com/~jasonrsmith/AB_Nut.dxf)
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
11-09-2003, 08:27 PM
Is there any demo version of Autocad 2000 that i can use to open the file? Please post the link if there is any.

ger21
11-09-2003, 08:55 PM
Autodesk's Volo View Express will let you look at the file, but not modify it.

http://usa.autodesk.com/adsk/servlet/index?siteID=123112&id=837403

Gerry

bobleecnc
11-09-2003, 09:16 PM
You can download a free dxf viewer from autocad website called
Voloview Express it will open other formats too I dont have the url. but its easy enough to find

Bob

chuckknigh
11-09-2003, 09:45 PM
I use a shareware product called IntelliCAD, and it works quite well. It's basically a clone of ACAD, and supposedly it'll even run AutoLISP programs...has the command line interface, too. All the good stuff.

Do a google search -- not sure if the latest version is still shareware, but the slightly older one will still work just fine.

-- Chuck Knight

balsaman
11-09-2003, 09:53 PM
I never thought I would tell another guy I like his nuts. Great job Kong.

:)

HiString
11-09-2003, 10:45 PM
This may clearly illustrate my newbie status, but what the hell...................has anyone made an anti backlash nut by using two standard nuts with a spring loading between them, forcing them out against the thread?

:cool:

Mr.Chips
11-10-2003, 12:16 AM
HiString.
Yes I have seen that method. The two nuts were captured in a tube with a spring between them and a o ring between the end of the tube and against the nut.
The spring is pushing both nuts apart from the center. One nut is trapped by the end of the tube, and the other nut is being pushed against the O ring. This causes pressure on one side of the thread of the shaft by one nut and the other side of the shaft from the other nut.
Might be wrong but this is how I rember it. If I am in error someone please correct me.
Hager

HiString
11-10-2003, 01:05 AM
Mr. C,

That is pretty well what I envisaged. Although I hadn't seen it done before, it seemed so obvious that I figured someone would have used that method before.

:cool:

kong
11-10-2003, 07:38 AM
The only problem with the spring method is that the spring must be strong enough to withstand the cutting forces, or backlash will still be present. That would mean a pretty strong spring, which may cause a fair bit of friction, and therefore wear on the nuts. The shop-bought sprung nuts use the spring to turn a thread, which pushes the two nuts apart. I found a description here (http://www.hpc-drives.com/drives/technical/Leadscrew_Tech.pdf), it's a pdf, check the last page.

DaSigntist
11-14-2003, 10:05 PM
Howdy,
I am making my anti-backlash nuts using the method as per Balsaman’s description (see picture below).

I think it's a simple adjustable way to achieve the minimum backlash.
I still need to spot weld the nuts to the washers and add a flange to connect to the axis but you can see its simple construction.
I am using nylon locking nuts on the small bolts.

Regards,
DaSigntist

ezland00
11-19-2003, 05:09 PM
Will can i find a 1/2-10 taps?

umrk
11-19-2003, 05:40 PM
Enco (http://www.use-enco.com/CGI/INPDFF?PMPAGE=272&PARTPG=INLMK3) carrys Acme taps. A friend and me went togeather and bought the 1/2x10 tandem tap. I haven't tried it yet but he said it worked great making a nut for the Z Axis for his CNC plasma cutter.

mike

ezland00
11-19-2003, 06:21 PM
thanks for the link UMRK

JFettig
10-08-2004, 09:32 AM
A free autocad copy would be a9cad at http://www.a9tech.com/download/

15mb and its basicly an autocad ripoff, works alright.

Jon

Ferenczyg
10-09-2004, 06:06 AM
this is a not so difficult to make ab nut, from http://www.wmberg.com/article970324.html

ESjaavik
10-09-2004, 02:22 PM
The only problem with the spring method is that the spring must be strong enough to withstand the cutting forces, or backlash will still be present.
If the spring is just pressing the nuts apart, yes. But if the spring is fixed to the nuts just making sure they both are snug against the ends of the capture tube. If you try to push the rod to the right, the right nut will press against the right end of the tube. And the other way around. The spring will screw the nuts apart so they always are up against their abutment with no play. The drawing does not show this, but the spring is trying to unwind, and is fixed to the nuts.

It works the same as the method with 2 nuts screwed into each other with a pitch different than the pitch of the rod, except the spring will constantly tighten them.

chuckknigh
10-09-2004, 05:29 PM
Ah, so it functions not as a compression spring, simply holding them apart...but as a torsion spring. Ingenious!

-- Chuck Knight

kevincnc
10-12-2004, 09:48 PM
Has anyone tried using something like UHMW, Delrin, or Nylon for a zero-backlash nut? It seem to me that you could grind the end of an acme screw to look (and work) like a tap, and you would get a nice tight fit. Maybe too tight though- I've been meaning to try it.

ger21
10-13-2004, 06:38 AM
Has anyone tried using something like UHMW, Delrin, or Nylon for a zero-backlash nut? It seem to me that you could grind the end of an acme screw to look (and work) like a tap, and you would get a nice tight fit. Maybe too tight though- I've been meaning to try it.


The majority of people here do just what you're saying. :D

cnc2k
10-24-2004, 01:53 AM
Can anyone make 3 of these nuts for me or make me a tap.

thanks

Ito-Brazil
10-26-2004, 08:44 PM
I´m having the same problem: how to make a good nut. I tryed to take a screw and make a hole maker wit it. But the hole got too tight and my motor simply can´t move it! What should i do? used NYLON to do the nut. Thanks guys!

mmech
06-25-2005, 01:19 AM
HiString.
Yes I have seen that method. The two nuts were captured in a tube with a spring between them and a o ring between the end of the tube and against the nut.
The spring is pushing both nuts apart from the center. One nut is trapped by the end of the tube, and the other nut is being pushed against the O ring. This causes pressure on one side of the thread of the shaft by one nut and the other side of the shaft from the other nut.
Might be wrong but this is how I rember it. If I am in error someone please correct me.
Hager

this is a fairly simple design but i have two questions. is the O ring necessary and are the nuts attached to the spring or does the spring spin independantly of the nuts?

mmech
06-25-2005, 10:16 PM
this is the picture to which i was reffering.http://www.cnczone.com/forums/attachment.php?attachmentid=950

H500
06-26-2005, 03:28 PM
The design looks like it will not work. The nuts look like they would just rotate with the threaded rod if the thread friction happens to be higher than the anti-rotation friction.

MikeAber
07-17-2005, 04:07 PM
I started out trying to make one of these acme nut jobs work 3 years ago and never could. While reading this thread this morning it came to me. I'm suprised I didn't see it here as there are many creative concepts in this thread.

Take two acme threaded nuts and place them on the lead screw with a spring between them. The length and power of the spring depends on how fancy you want to get. The spring pictured was removed from a unistrut nut just for illustration. The spring could be an "O" ring, a stack of belleville washers (the best option), or any other material you have on hand that will compress.

In the pictures you see two 7/8" 1/2" drive sockets, a deep socket and a standard depth socket. Use the deep socket for a long spring and the standard depth socket for a short spring stack.

If you attached a mounting flange on the acme nut on the right and slip a socket over the free nut and the lead screw you can tighten the loose screw against the spring to create any amount of tension against the two nuts you desire. Then slide the socket over the fixed nut and tighten a set screw installed in the side of the socket against the free nut to keep the socket from moving.

This alows the free nut to float on the lead screw with tension against both sides of the lead screw that can't rotate away from or toward the fixed acme nut on the flange, is totally adjustable and automatically adjusts itself for wear.

The socket doesn't need to be a quality one. A set of 10 belleville washers for this cost about $4.00 and the belleville washers can be stacked back to back (to increase power) or front to back (to increase spring travel) or a combination of both. The belleville washer information is from McMaster.com

Mike

carlnpa
07-17-2005, 09:42 PM
I made a cheap antibacklash acme nut assembly that works well by welding a fender washer to an acme nut with a compressed spring between. I posted a picture in frame 16 showing the parts, and frames 19 and 21 showing the assembly installed. That small spring does not need to be compressed much to take out the backlash.
http://www.cnczone.com/forums/showthread.php?t=7465&page=2