Low friction material for a bushing

P. Waller said:
Have the shafts coated or plated with a low friction material such as hard chrome or titanium nitride, make the bearings from a low friction low wear plastic material such as PEEK filled with PTFE and carbon as seen here https://www.ensingerspi.com/material.cfm?material=PEEK

This combination should last a good deal of cycles, everything may be done in the home shop aside from the plating or TIN coating.
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The company I work for has a sister company who can chrome plate but to be honest, I suspect that unless it was for a large batch the cost wouldn't be worth it. I am leaning towards a low friction plastic with a hardened shaft. I should be able to make these at a fairly low cost - as long as I get comparable life out of them compared to the stock ones I can have a heap in the toolbox and swap them out as needed. It's only a 10 minute job to do.

Someone suggested UHMWPE and some research into it makes me think it could be the most suitable material. It has a coefficient o friction comparable to PTFE however is much more abrasion resistant.

Whatever I use I'll look to seal them with a couple of O-rings as well as others have said.

Thank you all for your comments - they have been most helpful!
 
McMaster-Carr sells a nylon-kevlar composite that is claimed to be "ultra wear-resistant". They also have MDF-filled nylon. I have machined both using sharp HSS tools. I initially tried using a carbide-insert cutter on the composite, with poor results. If you do try the composite be prepared for long, stringy swarf.

I got the composite to experiment with making polishing bits for a machine at work, so it was deliberately exposed to abrasives. It held up quite well. However, I didn't need very accurate machining tolerances so can't say how easy it would be to make a bushing out of it.
 
Very interesting reading through this thread. I am amazed at the specialized plastics these days. In the fruit packing houses I used to work in we used 1/2" and 3/4" keystock as chain guides on the bin dumps and they needed to be cut out and changed every couple of seasons. The bins would come out of the field and be muddy and be washed in the dump so it was very muddy messy and even though the chain rollers rolled on the keystock it wore them out in no time. When we changed to UHMW guides that all went away. I never saw anybody have to change them except in a house that did radicchio. Something in radicchio it ate UHMW!

In another house we leased a cardboard box maker. We had guys from the company in and out of there all the time and I got to know them. If the boxmaker went down, the shed went down so it was a big deal and they had been struggling with the shafts in the rams that form the boxes wearing out. After going through all kinda of exotic hardened alloys they went to pins made out of Delrin. Yup, had to believe. And they made them a press fit. If it didn't shave off curls as they drove it home it wasn't right. I was VERY skeptical and kept a wary eye on it and they never went down.

So I bring this up because what if you had a Delrin shaft on UHMW bushings?
 
so here's another idea: If you go with Nylon or Delrin bushings, you can increase their life considerably by coting the mating surfaces in Plumbers Grease. It is used in a lot of Nylon plumbing assemblies and is hydrophobic (keeps the moisture out). You can then remove the shaft at intervals to clean up the outer mm or so that might accumulate detritus...
 
C-Bag said:
Very interesting reading through this thread. I am amazed at the specialized plastics these days. In the fruit packing houses I used to work in we used 1/2" and 3/4" keystock as chain guides on the bin dumps and they needed to be cut out and changed every couple of seasons. The bins would come out of the field and be muddy and be washed in the dump so it was very muddy messy and even though the chain rollers rolled on the keystock it wore them out in no time. When we changed to UHMW guides that all went away. I never saw anybody have to change them except in a house that did radicchio. Something in radicchio it ate UHMW!

In another house we leased a cardboard box maker. We had guys from the company in and out of there all the time and I got to know them. If the boxmaker went down, the shed went down so it was a big deal and they had been struggling with the shafts in the rams that form the boxes wearing out. After going through all kinda of exotic hardened alloys they went to pins made out of Delrin. Yup, had to believe. And they made them a press fit. If it didn't shave off curls as they drove it home it wasn't right. I was VERY skeptical and kept a wary eye on it and they never went down.

So I bring this up because what if you had a Delrin shaft on UHMW bushings?
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I hand't considered using plastics for both surfaces. My only concern would be that if the bore was drilled off centre then there would only be <0.5mm material on the shaft so not sure if it would deform under load.

Dabbler said:
so here's another idea: If you go with Nylon or Delrin bushings, you can increase their life considerably by coting the mating surfaces in Plumbers Grease. It is used in a lot of Nylon plumbing assemblies and is hydrophobic (keeps the moisture out). You can then remove the shaft at intervals to clean up the outer mm or so that might accumulate detritus...
Click to expand...

I hadn't considered using grease - I had always been under the assumption that plastic bearings should be run dry although I must admit I have no idea why I think that!
 
While derlin + nylon might be fantastic w/regard to low friction, there are other factors to be considered, like the load the shaft has to take when this here shock is in use! It's necessary to design for worst-case, because, you know, Murphy is always lurking in the wings......
 
SamI said:
I hand't considered using plastics for both surfaces. My only concern would be that if the bore was drilled off centre then there would only be <0.5mm material on the shaft so not sure if it would deform under load.
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I've always thought that a bushing should be softer or harder than the shaft, but not the same. I can't think of many things that use the same material for both the bushing and the shaft from the factory?
 
Delrin and UHMW are not the same material at all. The wiki on UHMW is very interesting......
 
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