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Swaging Fittings

Can I use a hand swage tool to attach aircraft eyes and forks to 5/32 rigging?

Tom Wood responds:
The word "swage" is used so indiscriminately by catalog companies that it confuses us all most of the time. And since the integrity of the terminal fitting on the wire rope is at stake, it is important that the right tool be used to install each fitting.

But before we even go there, let me say that I am not generally in favor of using aircraft swage terminals for sailboat rigging. Since the pin sizes are smaller than marine swage terminals, once your boat is rigged with aircraft parts, you’re generally stuck with them unless you’re willing to drill out chainplates and mast tangs, opening a whole new batch of engineering questions. But aircraft terminals were designed to move the flaps and other control surfaces of light planes, not for the corrosive elements, vibration, and high loads of sailboat rigging—that’s why there are marine parts.

First it is important not to confuse a swaging tool with a Nicopress tool. A Nicopress sleeve is an oval soft-copper part with twin holes for making a loop in a wire rope or for joining two wire cables. They are often plated to a shiny finish. The tool that installs these looks like a giant pair of pliers, or a bolt cutter, but it has one or more round holes in the working end to compress the soft copper onto the wire. Unfortunately, many companies that make and sell these tools refer to them as "swaging" tools, which they are not. There are even smaller versions of these that use a pair of bolts turned by wrenches to squeeze copper ovals (or stops and balls) onto a wire, and these are often referred to as hand swaging tools, which they are not. These tools are for use on very soft materials and cannot apply the enormous pressure to truly "swage" a real fitting onto a wire.

Now, if you want to get really confused, try to follow this. There are terminal ends made for lifeline usage that look just like a regular rigging terminals, but the part that is squeezed onto the wire is made of a softer alloy for use with, you got it, a Nicopress tool. These allow a rigger to build a new set of lifelines on the deck of a boat without the need to take all the fittings back to the shop. They are usually identified among the lifeline parts as "hand crimp" fittings and they should never be used for standing rigging.

OK, you with me so far? Here comes the next curve. There are true swaging machines that are portable and used by hand. For bigger sizes of wire rope terminals, these are often actuated by a small manual or hydraulic pump to draw the fitting through stationary jaws. There are also some manually operated hand swagers, but few boat owners would want to spend the thousands of dollars necessary to purchase one of these sets to re-rig his boat once every 10 years—I can hardly lift one.

One last bend in the road. Many riggers use what is called a roll swager, often made by and called a Kearney. These bolt to a bench and have sets of two wheels to compress the swage terminal onto the wire. It is operated with a long manual crank handle, although I have seen a few electrically driven units. Roll swagers are handy for small wire like your 5/32s of an inch on up to about 1/4-inch wire rope and are often used on lifelines and the standing rigging of small boats. Many traveling riggers have one bolted in the back of their truck or van. These put sufficient pressure on smaller swage fittings to give 100 percent strength of the wire.

The true rotary-swaging machine is a giant among tools. Most stand about five feet tall and weigh an actual ton or more. They have dies for each wire size that are hammered into the swage fitting multiple times by an interference-fit rolling hammer. In operation, they shake a concrete building and can be heard a quarter mile away, so there is no mistaking the fact that the terminal was beat onto the wire. These machines cost many thousands of dollars, a crane to install, and run on 220-volt, three-phase power—I’ve never met a recreational sailor that owned one.

So, with that long lesson, the answer to your question is "no!" Do not use what the catalogs sell as a "hand swager" for putting on swage fittings—they are only for copper sleeves and a few special lifeline fittings.

Tom Wood is offline  
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