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Thread: What lube on acme w/delrin nuts?

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    Silicone lubricant is excellent with delrin on steel. It even embeds a bit in the delrin.

    Just watch out if you use spray lubricant once spray gets on something you won't ever be able to paint it! Fortunately you can get simple liquid silicone lubes. I've used "Armor all" in a pinch, it works very well as a silicone lubricant.



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    Quote Originally Posted by RomanLini View Post
    Silicone lubricant is excellent with delrin on steel. It even embeds a bit in the delrin.

    Just watch out if you use spray lubricant once spray gets on something you won't ever be able to paint it! Fortunately you can get simple liquid silicone lubes. I've used "Armor all" in a pinch, it works very well as a silicone lubricant.
    Thank you RomanLini. That sounds like a good idea.

    John



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    I've come back to this thread as I have run into a problem. I bought a 36" acme rod with delrin nut from a different supplier on ebay and the nut is exceptionally tight and when I run the screw it makes a horrible shuddering sound.

    I've tried light oil, no good, motor oil, no joy, white lithium grease, helped some but not enough, next I tried something called tri flow, has teflon in it, and it did make the noise go away but its only a temporary solution as after several runs back and forth the noise comes back and I have to reapply, in fact if I wait overnight its almost like I never put any on. I've been hesitant to use silicon as I'm still in building stage and have several parts I still need to paint.

    any more suggestions?

    John



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    You could hacksaw a fine slot in the nut allowing it to flex and reduce the clamp force. I suggest not cutting too much, as they will settle in over time.

    Another suggestion would be to heat the nut and screw in an oven etc to get it up near the Thd (temperature of heat deformation) of the Delrin, this will allow the Delrin to reform slightly around the screw so it is not so tight. That method can risk damaging the nut if you get it too hot.

    Probably the first thing I would try is some silicone lube and "running in" the nut (just as it is) with a power drill, you don't have to do that anywhere near your paint. If it starts to run in ok you don't need the other methods. Running in a tight nut with a power drill causes the heat right at the thread surface, so it tends to reform plastic nuts quite well to be a good fit.

    I hope somehting there helps.



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    Quote Originally Posted by WoodSpinner View Post

    any more suggestions?

    John


    I always polish my home made taps before I make them....so the nuts
    are usually a little tight...(better a bit tight than a bit loose...)

    But my secret for making "perfect" fitting nuts is that I also make a secondary
    follower tap.

    These are all variations and are for different screw makers/batches/whatever
    causes the screws to be different from one time to the next...
    but you can see the follower tap with the handle for one of them.

    What that does is removes the tiniest bit of material each time you pass it
    through the nut. A couple times and a nut can be made nearly perfect.

    Mine was made with a grinder and has a fairly good sized notch in the end,
    but all it really takes is a small notch in the end of a scrap of acme...from
    the same screw you want to use...and it'll work perfectly.

    Worse case....a notch can be made even on a screw that there's no
    extra scrap of with a dremel cut-off wheel. Then if it's polished out
    really well after it's done it's job, it won't hurt anything.

    http://www.microcarve.com/forum001/taps/

    Maybe you can get an idea from that....


    John

    Attached Thumbnails Attached Thumbnails -taps2002-jpg  


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    Quote Originally Posted by RomanLini View Post
    You could hacksaw a fine slot in the nut allowing it to flex and reduce the clamp force. I suggest not cutting too much, as they will settle in over time.

    Another suggestion would be to heat the nut and screw in an oven etc to get it up near the Thd (temperature of heat deformation) of the Delrin, this will allow the Delrin to reform slightly around the screw so it is not so tight. That method can risk damaging the nut if you get it too hot.

    Probably the first thing I would try is some silicone lube and "running in" the nut (just as it is) with a power drill, you don't have to do that anywhere near your paint. If it starts to run in ok you don't need the other methods. Running in a tight nut with a power drill causes the heat right at the thread surface, so it tends to reform plastic nuts quite well to be a good fit.

    I hope somehting there helps.
    I'll probably try your last suggestion first, I'm a bit nervous about trying anything that could mess it up and end up with horrid backlash in it or just destroying it as with most builders I'm on a budget.

    I'll try running it in with silicone lube, I am going to write a small g-code to run that axis back and forth at speeds varying from 500 rpm to 1k rpm (50ipm, 100ipm) and hopefully that will do it. I've run it an hour or two with the Teflon but that hasn't eliminated it as of yet.

    Quote Originally Posted by microcarve View Post
    I always polish my home made taps before I make them....so the nuts
    are usually a little tight...(better a bit tight than a bit loose...)

    But my secret for making "perfect" fitting nuts is that I also make a secondary
    follower tap.

    These are all variations and are for different screw makers/batches/whatever
    causes the screws to be different from one time to the next...
    but you can see the follower tap with the handle for one of them.

    What that does is removes the tiniest bit of material each time you pass it
    through the nut. A couple times and a nut can be made nearly perfect.

    Mine was made with a grinder and has a fairly good sized notch in the end,
    but all it really takes is a small notch in the end of a scrap of acme...from
    the same screw you want to use...and it'll work perfectly.

    Worse case....a notch can be made even on a screw that there's no
    extra scrap of with a dremel cut-off wheel. Then if it's polished out
    really well after it's done it's job, it won't hurt anything.

    http://www.microcarve.com/forum001/taps/

    Maybe you can get an idea from that....


    John
    I have a screw from another vendor that is a bit rough in spots(has spots that look like it was starting to corrode) and perhaps if running it in doesn't work, I'll run that one through the nut a few times, I dont have any extra screw at present to attempt to make a tap. I do eventually intend to replace the corroded one so will have that to work with eventually.


    Thanks to both of you for your help, I truly appreciate it.

    John

    Last edited by WoodSpinner; 05-17-2012 at 11:04 PM. Reason: spelling


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    well, I've been running a "break in"/Wear in routine about a hour a day utilizing the silicon, so far so good, still getting noise at high speeds but I think in part thats because my screw is wobbling at those speeds. I'm going to find someone with a lathe around here to extend the bearing areas on the ends of the screws so I can use self locking nuts to secure the screws, as it is they are held by bearing pressure in from the ends placing the screws in compression which I believe is a large part of the screw whip I'm experiencing. So I'm hoping by locking the bearings to the shaft I will be able to put the screws in tension (just a little) in the hopes it will reduce the problems.

    Speaking of speeds, I went from using 5/16 18 tpi screws to 1/2 10 single start screws, I thought the difference in speed would be dramatic, like doublt what I was doing before but not the case..I'm curious, what speeds are others getting using acme screws like mine?



    Quote Originally Posted by WoodSpinner View Post
    I'll probably try your last suggestion first, I'm a bit nervous about trying anything that could mess it up and end up with horrid backlash in it or just destroying it as with most builders I'm on a budget.

    I'll try running it in with silicone lube, I am going to write a small g-code to run that axis back and forth at speeds varying from 500 rpm to 1k rpm (50ipm, 100ipm) and hopefully that will do it. I've run it an hour or two with the Teflon but that hasn't eliminated it as of yet.



    I have a screw from another vendor that is a bit rough in spots(has spots that look like it was starting to corrode) and perhaps if running it in doesn't work, I'll run that one through the nut a few times, I dont have any extra screw at present to attempt to make a tap. I do eventually intend to replace the corroded one so will have that to work with eventually.


    Thanks to both of you for your help, I truly appreciate it.

    John




  8. #20
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    75-100ipm is about the max you'll see from 1/2-10 single start.

    I get between 150-195ipm with 1/2-8 2 start, and a lot of people get 300-400ipm with 1/2-10 5 start.

    Gerry

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    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)


  9. #21
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    Absolutely, plastic nuts settle in very well after enough heat cycles as they re-form around the screw.



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    Quote Originally Posted by ger21 View Post
    75-100ipm is about the max you'll see from 1/2-10 single start.

    I get between 150-195ipm with 1/2-8 2 start, and a lot of people get 300-400ipm with 1/2-10 5 start.
    I'd just be happy to get 80ipm without the nut binding up and squalling. I am on a very ridgid budget so this was the best I could afford. Thanks for the ratings for the various screws, it will make a good reference once money becomes available.

    Thanks,
    John



    Quote Originally Posted by RomanLini View Post
    Absolutely, plastic nuts settle in very well after enough heat cycles as they re-form around the screw.

    well, I've run them quite a bit and here is where I'm at, so far silicon does the best to shut it up but only lasts about 15-20 minutes, each day I have to spray the screw down at the beginning and again every 20 minutes(wife suggested I just spritz it once in a while when its running) personally its driving me nutts, I'm now considering cutting it down one side as a relief and see what happens.

    John

    ps, if I dont continue to spray it it gets worse and worse until I cant move it at even 10ipm without it suddering/loosing steps and so on



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    If you have a Dremel, cut a slot in the threads near the end of the screw and run the nut over it a few times. It will act like a tap and loosen it up. Just don't make it too loose.
    See "What if my nuts are too tight?"

    If it's really tight, you may gain a little more speed if you can get it looser. Personally, I doubt it will really loosen up much on it's own unless you run it a lot, for quite a long time. Especially since you're lubricating it, as the job of the lubricant is to reduce wear.

    Gerry

    Mach3 2010 Screenset
    http://home.comcast.net/~cncwoodworker/2010.html

    JointCAM
    http://www.g-forcecnc.com/jointcam.html

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)


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    Quote Originally Posted by ger21 View Post
    If you have a Dremel, cut a slot in the threads near the end of the screw and run the nut over it a few times. It will act like a tap and loosen it up. Just don't make it too loose.
    See "What if my nuts are too tight?"

    If it's really tight, you may gain a little more speed if you can get it looser. Personally, I doubt it will really loosen up much on it's own unless you run it a lot, for quite a long time. Especially since you're lubricating it, as the job of the lubricant is to reduce wear.
    i got real close to doing that today, I pulled apart the 36" screw and nut and just for the heck of it, I tried swapping the nuts between the z and the y and voila a dab of lithium grease and its running at 100ipm without any noise at all, ran it for a couple hours and nothing so put the z back together and ran it and no noise, the noise didnt follow the nut....

    John



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