Swaging questions

[Brion Toss]

Hello,
I also would like to see any evidence of sealant affecting swage strength. It would have to be really compelling, because I definitely have seen assiduously drip-waxed swages splitting open from internal corrosion in the tropics, the same territory where sealed swages stay just fine. Show me the numbers.
ps,
There also seems to be a logical disconnect between metal-to-metal integrity and the effect of internal sealant in a swage; with Sta-loks and Hayn's, for instance, we've seen reliable test results up at or near the wire's actual break strength, even though the compression on these fittings is far less than with any swage.

[Brian Duff]

So...? is the answer, or concensus anyway, that the sealant doesn't hurt strength (as suggested by Brions' comments on Low-Compression mechanical fittings), but may or may not effect longevity depending on weather or not oxygen/salt/water isolation is better than free supply of water/salt, and on down facing terminals oxygen ?
Or , as I have notice when cutting swaged fittings open to inspect, there really isn't any room left inside the swage once it if swaged. I have noticed on new swages when cut open that I can hardly discern the outline of just some of the strands, as it all appears one solid rod, even when sanded and polished or cut rough. I must admit that I have not cut an older swage open in a while, but I will next time I come accross an example of both kinds, and post my results here. At our shop we do not use any sealant in any swage fittings we press, unless we are un-able to talk an adamant owner out of this practice.

One should note that the 'excellent' Hi-Mod Low Compression mechanical fitting Brion mentions only reccomends using a thread locker adhesive for final assembly, and not sealant, if I recall the directions properly... I must admit I only read directions for fittings I use regularly , on occasion, as opposed to every time I open one, as that would be really time consming considering the normally repetitive nature of instructions for the same fitting :: )

very interested in the results of this discussion, as I feel that every one of us should know the answer to this question.

[toolowd]

I will say that the Hayn insulators that I installed last fall are a wonderfully designed bit of functional art.

rich morpurgo

[arenyi]

I thought that I asked a simple question, but I see, even Brion doesn't have a simple answer.
I sliced my old swages (around eight years old) to learn what happened inside.
In the first slice, around 4 mm from the top the wires were very rusty. There is no doubt that it is the time to replaceÖ..
In the second slice, around 8 mm from the top, the metal was clear; however three rust dots were seen in the space between the wires. Is it "local" rust, or just dirty water that penetrated from the upper parts? I don't know. Anyhow, it is evident that internal sealant would eliminate this by filling the space between the wires.
The third slice, around 15 mm from the top, was absolutely clear.
Since the wires always break near the open end of the swage, I am not sure if the internal sealant can -for long term- really seal the open end of the swage and if water can penetrate under the seal, the situation may deteriorate.
I asked two local riggers and ñnaturally- both replied that they are "working exactly according the manufacturer's instructions, and they don't require any sealing".
It may be very interesting to see professional cutting of old swages, microscope photos and explanation of an expert in metallurgy. Maybe this was done by one of the swaging machine manufacturers?

[Brion Toss]

Hi again,
Very, very few riggers dip wire before swaging, and they tend to work in warm climates, where the effects of corrosion are greatest. Since most cruisers spend at least some time there, we work to do what we can to limit corrosion. I came to embrace the Dipping School while working in the South, and seeing side-by-side examples, with the undipped ones failing, and the dipped ones not. I have also cut apart numerous swages, of all ages and from all climates, and I can tell you that they are far from impervious to water. I can also tell you that crevice corrosion is a bit more complex than the absence of oxygen; otherwise any piece of stainless would corrode from the inside out. A surface oxide coating is stainless's defense, and it can be replenished in the presence of oxygen. But if you exclude both air and corrosive elements, like saltwater, deterioration is largely arrested.
The next time you see vertical cracks on a swage, know that internal corrosion ówhich always causes the corroded material to expand ó is trying to blow the swage apart (horizontal cracks usually speak to fatigue, though there might also be a corrosion component). This usually, as noted above, happens close to the top of the swage, but I have some samples in my shop that are cracking near the bottom.
As for Hayn's instructions, all I can say is that they are roughly the same as Norseman's and Sta-lok's once were; leaving sealant out works pretty well in low-salt, low-temperature climates like England, for there you can count on plenty of fresh water to rinse out salt, and also count on that water evaporating, helping that oxide coating. But as Norseman and Sta-lok found out, and as I predict that Hayn will, Tropical waters are an entirely different story, with a lot more heat and salt, and a lot less fresh water rinsing. That's why we see a lot of internal corrosion in unsealed and inadequately sealed compression fittings, and none in properly sealed fittings.
Fair leads,
Brion Toss

[Brian Duff]

Yes, I also have cut some of our old swages apart, and can see dark (probably 'rust' colord) lines showing me the strnad pattern, which implies that moisture does make its way down into the swage, as others here seem to have noted to. So I guess that means that we should be using sealant in swage terminals to try to keep the water, and everthing else out ?

From what I have noticed on many occasions, with hardware such as chainplates and tangs, stainless steel does seem to just "corrode from the inside out". One sees the tight pocket of rust on the surface, and starts sanding of wire brushing looking for a crack, usually finds a crack, and with further investigation realizes that much of the mateial in that area is riddled with 'crevice corrosion' or a network of voids 'caves and tunnels' benieth the surface. It has always seemed to me that stainless does just corrode away on its own, but I suppose that really these are the effects of electrolisis.

Like was noted, or swage manufacture, if I remember correctly, tells us to swage dry, is that really the best thing to do. I still think there hasn't been a definate answer. Or mabe this is another typical boat question, with an answer that varies from with region and preference ?

The next question would be what sealant to use, as I have 'heard' that silicone is not good to use with stainless becasue it is corrosive, but the sta lok instructions call for silicone. I typically use a polyurethane when assembling mech fitting, and have not recieved any bad reports ...

[Brion Toss]

Hi again Brian,
Let's leave the sealant question aside for a moment, and address some of the points in your most recent letter. Stainless does not, in fact, "corrode from the inside out", or at least not the way I meant it. Crevice corrosion has to eat into the metal from a surface; it can't start on the interior. So when you find a crack, it will always have propagated from a surface. That's why we polish metal surfaces, and construct them from corrosion-resistant alloys: to prevent corrosion from affecting the surfaces.
Electrolysis is a specific kind of corrosion, quite distinct in cause from crevice corrosion. Electrolysis is a galvanic reaction fueled by live current. It can coexist with crevice corrosion, as can chloride corrosion, stress corrosion, etc., but it definitely should not be confused with it. And if you see evidence of electrolysis in a swage, you probably have much more serious issues than cracks, anyway.
Now back to sealants. It is true that most silicones are mildly acidic, but to a trivial degree, and even then only before it has cured. Automotive silicone is usually low-acid, because gaskets are more readily affected by acidity than large chunks of stainless. But there's a better reason not to use any type of silicone in a terminal: it is less efficient at maintaining adhesion than other goos, particularly over wide temperature changes. We've found that 3M's 4000 or 101 are far more stable, yet not so adhesive that they make reusing the terminals diffcult.
Arenyi noted, in a previous letter, that "...wires always break near the open end of the swage...". If only it were true. Many times we've found broken wires inside swages, a consequence of corrosion from water intrusion.
Fair leads,
Brion Toss

[Brian Duff]

One more swaging question .
When using a roller swaging machine should the swage be rotated 90* for the second pass, or should the ridge be left intact and the swage pulled the same orientation twice ?

I have been taught that the swage should be rotated to yeild a more 'smooth' apperance and feel(safer), and to force more metal and more pressure by pushing all the material into less space.
Then the other day somebody once again asked the question, doesn't that push the swage open by pressing it 90*, or cause excess fatigue right off the bat ? I always have argued against this , and turned my swages. Today I noticed once again that the swages supplied by Selden Masts have the ridge proud on each side, so whats up ?

[Bob Pingel]

To start with I would use rotary swaging over roller -- you end up with a more symmetrical swage.

If forced to use roller swaging, I would swage only once, don't turn 90 degrees to smooth the ridge. The second swage will fatigue to body of the fitting.

Also, make sure the roller swager is in spec/adjusted correctly.

Bob

[Russ L]

Brian wrote:
"One more swaging question .
When using a roller swaging machine should the swage be rotated 90* for the second pass, or should the ridge be left intact and the swage pulled the same orientation twice ?"

Hi Brian,
I agree with the "one pass" camp. Stainless steel hates to be worked... it's kinda like a bureaucrat, I guess. Also, the second pass will expand the outside dimension of the first pass. The outside diameter is critical to the integrety of the swage, so if you expand it slightly it will loosen the "grip" a bit.
Cheers, Russ