Mechanism with two rubbing plates. Need help selecting materials. . .

[blademaker25]

I'm currently working out some details on an OTF (out the front) knife design.

I have two plates that rub together. One plate (separation plate) is .040" thick, and has a constant thickness. At this point I'm leaning towards 301 full hard. Because it's flat, will be laser cut, with only a couple of reamed holes. The other plate (trip plate) is machined out of .125" thick material, with some heavy machining. I'm trying to stay away from martensite steels, as I don't want to deal with heat treating the part.

I've found some literature that goes into detail about the galling, and wear of several stainless materials. The problem is that the tests on 301 are minimal, and they only tested the 301 soft, with a rockwell of B90. The full hard version of 301 is C41, and according to the literature has 'anti galling' properties, and good wear.

Materials I've eliminated are: All the martensite steels, including 410, 416, 420, 440C, as they all require a heat treat. I've also eliminated N50, N60 and other exotic materials, as the prices start to get too high.

Materials I'm looking at are : 316, 303, phos bronze, AL bronze. I can't find anything that shows the wear rates or galling when paired with 301FH.

I'm leaning toward 316, as it shows good wear and anti galling when paired with 416, and 440C. The 416 being in the C40-45 range, and 301 coming in at C41, I figured it might be comparable. But again, I can't find any data with 301 and 316 being used together.

Any help would be appreciated.

Gavi

 

[tbuelna]

Can you provide a sketch of your design, including how each material is used? Austenitic stainless steels seem like a poor choice for a knife blade. Heat treating a conventional material like 440C for your blade is not that difficult to do yourself and get a satisfactory result. Depending on how the mating parts (separation plates?) work, a material like Al-bronze or even a high-strength thermoplastic like PEEK might be best.

 

[EdStainless]

Look at tables 1 and 2.
If you need strength and corrosion resistance I would go with Nitronic (40, 50 or 60) and 17-4PH.
Though PEEK with PTFE loading in it would work great.

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P.E. Metallurgy, Plymouth Tube

 

[blademaker25]

Tbuelna,
Thank you for your response. The blade material is going to be 204p-cts, which is a carpenter steel. The parts that rub together would be the separation plate, and the trip plate.

Edstainless,
I'm planning on ordering some 17-4ph tomorrow, along with some more 301. Some people have suggested just running the 301 on it's self, but maybe having one piece 3/4 hard and the other full hard. I really like the N60 and N50 grades, but they are very expensive. I'm hoping I can find something cheaper. The alternative is to figure out the pricing difference between running both parts in 301, but doing a hard chrome platting on one verses the N50 or N60.

I had read the original document "review of the wear and galling characteristics of stainless steels", which looks like is the source of the tables in that pdf you attached. I find it strange that in the original document they briefly talk about 301, but only in the soft state, which is B90. And not in the full hard state which is C41, and in all the literature I can find on 301fh, it describes it as having anti galling properties and good wear resistance. Even the soft 301 has good wear resistance when paired with itself.

I built a machine to open and close the knife. No matter which direction I go, I will be able cycle the knife on there and watch for galling.

I've added a video of an earlier version of my OTF design. This old design uses rollers hidden underneath the button to stop the two plates from rubbing. In this case the materials are 410, and titanium, but don't actually rub. In the newer version I've simplified the mechanism, and have gotten rid of the rollers.

Deadlock take down video

Gavin

 

[EdStainless]

I believe that Nit40 (21-6-9 or 219) should be readily available as hard rolled sheet. All that I work with is annealed so I can't help you much. Try Ulbrich, they are a re-roller and might be able to tell you who they make it for.

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P.E. Metallurgy, Plymouth Tube

 

[dgallup]

Another vote for Nitronic 60 as a first choice but it is expensive. Ulbrich rolls Nitronic 60 for us but way thinner than you are looking for. You might want to try 305, we use it in a rubbing application against heat treated 8620 and it does well.

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[EdStainless]

I wouldn't self-mate 3xx alloys even when they are different hardness.
Hard 301 vs 17-4PH should be OK, but the Nitronics are in another league.
An alloy like 201LN would be a good option also.

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P.E. Metallurgy, Plymouth Tube

 

[tbuelna]

Gavin,

Took a quick look at the video link you provided. I did not really see any surfaces of the separation plate where galling would be a concern if a suitable material is used and the design of the contact interfaces are optimized.

Also noted that you have opted for Carpenter CTS 204P corrosion resistant alloy for the blade. In your OP you mentioned you wanted a cres alloy that did not require heat treatment. So I assume you realize this alloy requires a very specific heat treat process to obtain optimum properties, including post rough machine stress relief, heating/austenitizing in a controlled atmosphere to minimize decarburization, quenching at controlled rate, sub-zero (-100degF) treatment to minimize retained austenite, and tempering at specific time/temperatures. Not something most people have the capability to do themselves. However, you can have this done at a smaller heat treat vendor for a lot charge of maybe $500, which is reasonable on a per-part basis if you intend to make more than just a few parts. Also, have you checked availability of the raw material? It's a specialty alloy, so unless you can get it from a knife supply, you probably won't have much luck finding it anywhere else in the quantity you require.

 

[blademaker25]

Thank you everyone for the responses!

I'm going to try harder to find a supplier for the Nitronic steels. And I'll get in contact with Ulbrich.

I've gone ahead and ordered some more 301, and 17-4ph to try. I'm going to try matting the 301 to itself, 301 to the 17-4, as well as send them out for some boron coatings from this company [URL unfurl="true"]http://www.richterprecision.com/[/url] Then do a cost analysis on the different options. My gut tells me that my best option is to make the separation plate out of 301, have it coated, and make the trip plate out of 301 uncoated.

Tbuelna,
I might not have been clear in my original post, but I'm only concerned with heat treating of the trip plate, and separation plate. The blade has minimal machining before heat treat, and only gets ground after. I've been using CTS-204P on all of my knives for quite awhile. I send all of the heat treat out to Peters Heat treat, and they specialize in exotic knife steels. The knife in the video is actually my custom version, which doesn't have a separate 'separation plate', instead the frame and separation plate are integral. But in that older configuration the trip plate and separation plate don't rub, instead there are rollers underneath the button which suspends the trip plate, so that it doesn't rub. I've been working on this OTF design now for about 5 years, and starting making them about 2 years ago. But they've been high end customs that sell in the $1,000 -$2,000 range. I'm now teaming up with a local OEM company to start manufacturing a newer simplified design, but i'm still in the prototype stage for the newer version.

For a little more background on myself, you can check out my website and see some of our older designs. We're a father son team that specializes in mechanisms for knives. In the past we've been focused only on R&D, but with this new design we're starting to focus on production.

[link www.hawkknifedesigns.com]
www.hawkknifedesigns.com[/url]

Gavin

 

[dgallup]

Gavin

You can do an ion nitriding heat treatment on 300 series austenitic stainless steel that will greatly increase wear resistance. Ion nitriding is a line of sight process so it will only harden the surfaces directly exposed to the ion beam (there is a little wrap around on corners). In high volume production it's cheaper than most plating but may not be at low volumes. We have found it to be more dimensionally stable and consistent than plating and get tremendous wear resistance from it. We have been doing it on fuel injector parts for 30+ years and the things never wear out, regularly go over 1 billion cycles. Probably way overkill for you application, hard to imagine a knife needing more than 10 thousand cycles but I know the custom knife industry likes overkill. I'm a collector myself.

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The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.