Lubricant for nylon rod in iron tube

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Discussion Overview

The discussion revolves around the selection of a suitable lubricant for a nylon rod operating within a mild steel tube, specifically for an all-weather application involving a latch release lever. Participants explore various lubrication options, considering factors such as conductivity, environmental conditions, and maintenance requirements.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • One participant suggests that no lubricant may be necessary due to the low bearing loads and the potential for grease to attract dirt, which could be abrasive.
  • Another participant proposes the use of plastic bushes to prevent corrosion of the mild steel tube and suggests considering stainless steel or aluminum for the rod to avoid corrosion issues.
  • A retired locksmith shares a preference for powdered graphite but raises concerns about its electrical conductivity, questioning its suitability given the application’s requirements.
  • Discussion includes the potential use of Teflon spray and silicone spray, with varying opinions on their conductivity and effectiveness.
  • Beeswax is mentioned as a simple and inexpensive lubricant option, noted for its durability and temperature tolerance.
  • One participant introduces the idea of using molybdenum disulfide (moly) as a dry lubricant, discussing its properties and potential benefits when mixed with nylon during polymerization.
  • Concerns are raised about the presence of weld seams in the steel tube, which may necessitate the use of bushings for smooth operation.

Areas of Agreement / Disagreement

Participants express differing opinions on the necessity and type of lubricant to use, with no consensus reached on a single best solution. Various lubrication methods are proposed, but the discussion remains unresolved regarding the optimal choice.

Contextual Notes

Participants note that the specific type of steel tube and its interior smoothness may influence the need for lubrication. There are also unresolved questions about the conductivity of certain lubricants and their implications for the application.

Who May Find This Useful

This discussion may be of interest to individuals involved in mechanical design, materials science, or those seeking practical solutions for low-maintenance applications in varying environmental conditions.

jim mcnamara
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This is way outside my area.

I have a 4" long 1/2" D. rod of 6/6 nylon, inside a mild steel tube. The application is all-weather. Length of rod travel is .70 to .75 inch. Light use, 20-50 actions per day.
The application is an oddball latch release lever. Nylon was chosen because of cost and it is a non-conductor.

What lubricant if any should I consider? It will live out in the boonies so I want to make the fewest possible number of pilgramages for maintenance. And any moving part is the likeliest point of failure.

Thanks folks.
 
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Hi Jim. I use a lot of plastics, generally filled Teflons, for wear items that move against smooth, metal surfaces. All parts are dry. The use of a plastic in this application seems very reasonable, and I wouldn't suggest any lubricant. Any kind of grease is going to collect dirt which will be abrasive. There are dry lubricants such as graphite or molydisulfide, but for your application, it doesn't sound like you have high bearing loads or high velocity. I would suggest simply making sure you have clean, smooth surfaces and you should find something like that should last forever.
 
In an all weather environment you might think about using plastic bushes to support the rod, so you don't have any long term problems caused by corrosion of the mild steel.
 
I sort of (?) agree with Q on this. As a retired locksmith, my lubricant of choice has always been powdered graphite. The only reason that I won't recommend it in your case is that you mentioned conductivity. I assume that you mean electrical conductivity, rather than thermal or optical. Graphite is one powerful conductor. (I couldn't use it on dash-mounted ignition switches in case of causing a short-circuit. Column units use tie-rods to the actual switch, so that isn't an issue with them.)
You can get Teflon in a spray can, or at least you used to be able to. I'm not sure about now, since the substance has been classified as hazardous. There is also a silicon spray that is incredibly lubricative, but I don't know what the conductivity level is.
Q, how do you consider moly disulphide to be dry? The only version available where I live has the consistency of margarine. I used it and lithium grease interchangeably.
 
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AlephZero said:
In an all weather environment you might think about using plastic bushes to support the rod, so you don't have any long term problems caused by corrosion of the mild steel.
That's a good point. The steel rod will corrode. Might consider making it from 300 series stainless steel or aluminum.

Danger said:
Q, how do you consider moly disulphide to be dry? The only version available where I live has the consistency of margarine. I used it and lithium grease interchangeably.
I've used Dow Corning Molykote 321 on 300 series stainless quite a bit to prevent galling. Works great. Spray it on and let it dry, it creates a coating that won't rub off easily. I've also noticed that it helps prevent corrosion. It can also be baked on for a more durable finish.
 
Q, your link just takes me to the Google home page, but I get the idea. I've never heard of it being available as a spray. I have no need for such a thing any more, but I'll certainly keep it in mind if such a situation arises again. The reason that no oil product, including WD40, can be used in a lock is that it collects dust and turns into mud, and then into cement if left long enough. Any dry compound is nice. (And, where I live, it has to be functional down to about -50° C.)
 
Bees wax would be a simple and cheap solution. Available in any hardware store for applications like this.
 
That link worked, Q. A tad pricey, perhaps, but worth it if its characteristics are required. Thanks for bringing it to my attention. I did notice from the ad, though, that it also contains graphite. That once again raises the conductivity isssue.
I also like Aleph's idea about bushings, but is there room for them? If the bolt is a tight slip-fit, as is implied, a larger diameter tube would have to be subbed in.
I never thought of wax, but sometimes low-tech is best. It's certainly simple and inexpensive to use, and has pretty good durability. It also has excellent temperature tolerance and won't wash away if rained upon.
Come to think of it, Jim, what exactly is the issue with conductivity? Latches are part of my knowledge base, and I can't think of a single instance in my experience wherein the actuator had to be insulated. :confused:
 
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  • #10
jim mcnamara said:
... I have a 4" long 1/2" D. rod of 6/6 nylon, inside a mild steel tube. The application is all-weather. Length of rod travel is .70 to .75 inch. Light use, 20-50 actions per day. ...

Much will depend on the specific type of steel tube you choose. The most common, inexpensive tubing may have a weld seam inside. For this, you may indeed require bushings to provide smooth operation.

Assuming the tubing has a relatively smooth interior, and the rod isn't a tight fit inside the tube, then lubrication is optional. (Depending on acceptable working force limits.) I like "dry" lubricants containing either moly or Teflon. If you can't find them at the hardware store, try a bicycle shop.

Another option is "moly-filled" nylon:
Finely divided particles molybdenum disulfide are evenly dispersed throughout the nylon material during polymerization. Molybdenum disulfide particles act as a dry lubricant; thus the addition during polymerization enhances nylon's already load bearing and wear capabilities while maintaining its impact strength and toughness. With a lower coefficient of linear thermal expansion than nylon 6/6, Moly-filled nylon provides a degree of self-lubrication suited to applications where external lubrication is impractical, contaminating, or difficult to maintain leading to an improvement in wear. This, combined with lower water absorption extends the range of applications that MoS2-filled nylon has over regular cast nylon 6.
http://www.emcoplastics.com/index.cfm?fuseaction=product.display&product_ID=35&ParentCat=16
 
  • #11
Good post, Pantaz. I've never heard of polymers being permeated with lubricants before. I knew that nylon is self-lubricating, but never how it was.
 

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