Swaging questions

[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

[Brion Toss]

Hello,
Oh, dear. As far as I know, only Wire Technic (sp?) swages are suited for single-pass swaging; standard Kearneys specifically require two passes, with the second 90? to the first. Yes, this makes for fatigue, but one pass simply doesn't compress enough metal far enough. Make two passes ó and no more than that, or fatigue happens in a bigger way ó unless the machine manufacturer says otherwise.
We see far fewer fatigue problems with rotaries, and the ones we do see are often from machines that have gotten out of spec. This seems to happen rarely with rotaries, and I can only speculate that this is because the much more expensive machine tends to end up with much more careful people. Kind of like being more likely to attend to oil changes with a Rolls than with a Yugo.
Fair leads,
Brion Toss

[Brion Toss]

Hi Brian,
Most Kearney-type swagers need to be turned 90? for the second pass, according to their manufacturers. The dies prevent the second pass from undoing the compression of the first pass, but as I understand it, fatigue from the radical distortion of metal is much more of a problem than with rotary swages, which bring the metal down in smaller, smoother increments.
There will still be a ridge showing, with a Kearney-type machine, even if you turn it 90?, unless either the machine or the operator has some trick way of preventing or minimizing this (in other words, to try to make it look like a rotary swage).
What you might be seeing from Selden is the product of a WireTecnic (sp?) machine, which leaves a very pronounced ridge, almost a fin, on either side. And with these machines, one is instructed not to make a second pass. The back story here is that the WireTecnic machine, unlike its cousins, pulls the swage along by its end; every other Kearney-type machine powers the dies. The idea is that, with unpowered dies, one can get less deformation in the machine ó the metal of the swage compresses more at its own rate, with a constant pull, instead of being forced through at the rate set by gearing. Or that's how I understand it. These swages have a very good rep in Europe, where they originated, but haven't much caught on here yet. This might in part be due to their appearance, which isn't smooth like we're used to. Some shops will grind off the flashing, which strike me as a bad idea for at least a couple of reasons, and which adds noise, hassle, and time to the swaging process. And one outfit in Seattle still, as far as I know, makes repeated passes with their WireTecnic, to eliminate the flashing. When I suggested that this might be a time-consuming way to accelerate metal fatigue, the machine operator said that his manager, who was an engineer, said that's the way to do it. An engineer. Right.
Fair leads,
Brion Toss