A swage is a metal fitting pressed onto the end of a wire rope so tightly that the metal of the fitting flows into the lay of the wire and grips it permanently. Swaged terminals are the standard way of ending standing rigging: the eye, fork, stud or T-ball at the end of your shrouds and stays is almost certainly a swage. A beginner learns that the swage is the smooth stainless sleeve where wire becomes fitting; an experienced sailor knows that the swage is also where wire rigging most often fails, and that reading the condition of a swage is a core skill in deciding whether a rig is safe for another season.
How a swage is made
The wire is cut cleanly and inserted into the bore of the terminal, which is a stainless steel sleeve slightly larger than the wire. The terminal is then compressed in a swaging machine. Rotary swagers hammer the fitting from all sides as it is fed through, producing a round, even finish; roller swagers pass the fitting between shaped rollers, usually in two passes at right angles. Either way the sleeve is squeezed down onto the wire so hard that its inner surface conforms to the individual strands. The finished swage should be straight, round and of a diameter within the manufacturer’s tolerance. A rigger will check it with a go/no-go gauge, and a swage that is oversize has not gripped, while one that is banana-shaped has been fed unevenly and is weakened.
Swaged versus mechanical terminals
- Swaged terminals: compact, light, inexpensive and neat, and they develop close to the full breaking strength of the wire when done well. They can only be made with a machine, so replacement means a trip to the rigger, and they cannot be inspected internally.
- Mechanical terminals (Sta-Lok, Norseman, Hi-Mod and similar): assembled by hand with a cone or wedge that splays the outer strands inside a threaded body. Heavier and more expensive, but they can be fitted on board, taken apart for inspection, and reused with a new cone. Many offshore cruisers carry them as spares precisely because a swage cannot be replaced at sea.
Why swages fail
The swaging process work-hardens the stainless steel and leaves residual stresses in the sleeve. Salt water wicks down into the gap between wire and terminal and sits there, and in that oxygen-starved crevice stainless steel corrodes. Over time hairline cracks develop along the length of the swage, usually starting at the lower terminals where water collects, and the sleeve eventually splits. Bending is the other killer: a swage is meant to be loaded in a straight line, and if the toggle does not allow free movement the wire fatigues where it enters the swage and strands break one at a time, out of sight inside the sleeve.
Inspection
Look at each lower swage closely at least once a season and after any hard passage. Wipe it clean and check under good light, ideally with a magnifying glass. Longitudinal cracks, even fine ones, mean the terminal must be replaced. Rust streaks weeping from the mouth of the swage indicate corrosion inside. A single broken strand at the entry to the terminal is a warning; the wire is failing. Check that the fitting is straight and that the toggle or pin it hangs on is free to articulate in the direction the wire moves.
The sailmaker’s interest
Rig failure ends a season, and a lost rig often takes the sails with it. Standing rigging that has stretched or whose terminals have begun to give changes the headstay sag and mast bend that a sail was designed around, so a genoa that used to set beautifully starts to look full and the boat loses pointing. When a customer at a UK Sailmakers loft complains that a relatively new sail has gone baggy, one of the first questions asked is when the rig was last inspected and tensioned. Fresh wire with sound swages, properly tuned, is part of getting the best from any sail.
Related terms
Standing rigging is the fixed wire or rod that supports the mast, ended by swages or mechanical terminals. A stud is a threaded swage that screws into a turnbuckle or rigging screw. A toggle is the articulating link between terminal and chainplate that prevents bending loads reaching the swage. 1×19 is the stiff, nineteen-strand construction used for most standing rigging and the wire swages are usually made on.
Frequently Asked Questions about Swage
How long do swaged rigging terminals last?
Ten to fifteen years is the common guidance for a boat kept in temperate waters, with tropical and hard racing use shortening that considerably. Insurers often ask for replacement at ten years regardless of condition.
Can I make a swage myself?
Only with a proper rotary or roller swaging machine, which is a workshop tool. Hand swagers are fine for small lifeline wire but not for standing rigging. For on-board repairs carry mechanical terminals instead.
A swage is a small, unremarkable piece of stainless steel doing an enormous job. Learn to read it, replace it on schedule rather than on failure, and the mast it holds up will stay where it belongs.