Description
The Fitting That Lets Two Incompatible Coupling Systems Work Together
Overhead line hardware uses two coupling standards that do not mate. Ball-and-socket couplings, a forged ball dropping into a socket, retained by a clip, carry most insulator strings. Clevis-tongue couplings, a U-shaped jaw closed by a pin, receiving a flat tongue, carry a great deal of clamp and link hardware.
Sooner or later a string needs both. The insulators are ball-and-socket. The clamp, the link, or the plate beneath them is clevis-tongue. Something has to translate.
That something is the socket clevis: a socket at one end to take the insulator’s ball, a clevis jaw and pin at the other to take a tongue. One fitting, two coupling languages, and a string that assembles instead of arriving in two halves that don’t meet.
If you are reading a string drawing and asking which coupling fitting goes here, this page will settle it in about ninety seconds.
Socket Clevis, Socket Eye, Ball Clevis, Ball Eye, Which One?
Four fittings, one simple logic. Each has a coupling end (ball or socket, facing the insulators) and an attachment end (eye or clevis, facing everything else):
| Fitting | Coupling end | Attachment end | Use when |
|---|---|---|---|
| Socket clevis (this page) | Socket – receives insulator ball | Clevis jaw + pin | The hardware below is tongue-type |
| Socket eye | Socket – receives insulator ball | Closed eye | The hardware below is eye, hook, or eye-bolt type |
| Ball clevis | Ball – enters insulator socket | Clevis jaw + pin | The structure attachment above is tongue-type |
| Ball eye | Ball – enters insulator socket | Closed eye | The structure attachment above is eye-type |
The rule that prevents most wrong orders: the coupling end is decided by your insulator (its ball or socket, and its designated size); the attachment end is decided by whatever the fitting connects to (eye or tongue). Read both off the drawing, not off the part you ordered last time.
And never assume the two coupling families interchange. A ball-and-socket fitting will not connect to a clevis-tongue fitting, however similar the load ratings look. That’s precisely why the socket clevis exists.
Specification Table
In the meantime, the coupling and load-class context that is verified across our range:
- Designated coupling sizes: 16, 18, 20, 24 and 28 mm across the ball-and-socket family, matched to your insulator
- Socket-family rated failing loads: 70 to 300 kN
- Ball eyes: 70 to 420 kN
- U shackles: 70 to 170 kN
- Yoke plates: 100 to 600 kN
- Clevis link patterns: Z-type 70–300 kN and PD-type 70–200 kN, for the connections either side of the coupling fittings
Sizes outside these ranges are forged to your drawings, with confirmation drawings issued before production.
The Clevis Pin: The Component Buyers Forget to Specify
A socket clevis has two independent retention systems, and only one of them gets attention.
The first is the socket’s retaining clip, the split pin or W-clip locking the insulator ball into the socket. (Its correct installation is covered on our socket eye page; the discipline is identical.)
The second is the clevis pin, the bolt or pin closing the jaw, with its nut, cotter, or locking arrangement. It carries the full string load in shear, sits at height, and is the component most often under-specified on an order. Three things worth getting right:
- Specify the pin type with the fitting: Bolt-and-nut, headed pin with cotter, or the pattern your utility standard names. Pins supplied with the fitting mean nothing gets improvised on the tower.
- Specify the locking provision: A pin that can back out under vibration is a coupling with a countdown on it. Split pins, lock nuts, or the arrangement your standard requires, stated, not assumed.
- Order spares: Pins and cotters are dropped from height at a rate every stores manager recognizes. A modest spares allowance costs less than one crew standing idle waiting for a part worth a few cents.
We supply pins and their locking components with the fittings, in the pattern your standard specifies, for exactly this reason: the coupling and its retention should be one purchase decision, not two.
Why Buyers Choose DAPENG Socket Clevis Fittings
- Forged in one piece: Hot-forged carbon steel with no welds in the load path, the entire string’s load passes through the socket wall and the clevis jaw, so the strength has to be in the grain of the steel.
- Socket geometry to the coupling standard: The ball seats fully and articulates freely; the clip channel accepts a properly seated retaining clip. Sockets machined loosely wear; sockets machined tight fight the crew installing them.
- Jaw and pin dimensioned to mate first time: Jaw opening and pin diameter matched to the tongue fitting below, confirmed against your drawing before production, because a coupling that’s correctly rated and dimensionally wrong is still a coupling in a box.
- Galvanizing you can measure: Hot-dip galvanized to ISO 1461 / ASTM A153 class coatings, verifiable with a gauge at goods-in socket interior included, where thin coating fails first.
- Batch load-tested, with paper: Test reports accompany every shipment, so your safety factors rest on tested figures and your client’s inspector has documents to review.
- The complete string from one factory: Socket clevises ship with the ball eyes, ball clevises, socket eyes, U shackles, yoke plates, insulators and terminal clamps of the same assembly, matched in load class, kitted per structure.
Use-Case Deep Dive
Where does a socket clevis sit in a suspension string?
At the lower end, immediately below the insulators. A standard suspension assembly runs: structure attachment → U shackle → ball eye → insulator string → socket clevis → suspension clamp → conductor.
The socket takes the ball of the final insulator; the clevis jaw takes the clamp’s tongue. On tension assemblies the terminal fitting changes to a strain clamp, bolt type tension clamp or preformed tension clamp; on twin-string or bundled arrangements a yoke plate enters the chain and becomes the component to match. Where an armor grip suspension assembly is specified at tangent structures, its housing attachment determines whether a clevis or eye fitting is required above it.
How do I choose the load class?
Match it to the string, and never undercut it, an insulator string is rated at its weakest component. Our coupling and link fittings run in matched classes precisely so a coherent string is easy to build: quote the string’s design rating once with your RFQ, and every fitting comes back in the same class with nothing quietly capping the assembly.
The failure mode this prevents is specific and expensive: a correctly-specified 120 kN string with a 70 kN coupling fitting somewhere in the chain is a 70 kN string, and the limiting component is at height where nobody inspects it.
Can you match into a string built by another supplier?
Yes, with two checks in writing. Send the coupling designation (the ball/socket size), the rated load class, and the tongue or jaw dimensions of the fittings the socket clevis will sit between, or samples, or clear photographs with a rule in frame. We confirm mating and load class before production.
Mixed-supplier strings are entirely normal on networks built across decades. The risk isn’t the mixing; it’s assuming everything in the chain shares a rating and a coupling family when nobody has checked.
Specifications, and What They Mean for You
| Specification | What we supply | What it means for the buyer |
|---|---|---|
| Body | Hot-forged carbon steel, one piece | No weld in the load path at a full-load coupling |
| Coating | Hot-dip galvanized, ISO 1461 / ASTM A153 class | Decades outdoors; thickness checkable, socket interior included |
| Coupling sizes | 16, 18, 20, 24, 28 designated; custom to drawing | Matches your insulator’s ball designation exactly |
| Load classes | 70-300 kN socket family; matched across the string range | Nothing in the chain caps the assembly |
| Pin and retention | Pin, nut/cotter and locking provision supplied | Coupling arrives complete; nothing improvised at height |
| Verification | Batch load testing, reports with shipment | Safety factors calculated from tested numbers |
Straight Answers to Common Buyer Concerns
“How do we verify a forged coupling is rated as marked?” Test it before it ships and check it when it lands: batch load-test reports with every order, galvanizing thickness measurable at goods-in, and third-party pre-shipment inspection (SGS/BV or your nominated agency) welcome at the factory. On string hardware we would rather your inspector confirmed the rating at our gate than your outage report questioned it later.
“Our utility standard specifies a clevis geometry we don’t see listed.” Then we forge to it. National utilities specify jaw dimensions, pin diameters, coupling designations, marking and sometimes proof-load documentation, building to a customer’s drawing is the majority of our export work, not an exception. Send the specification page or a sample fitting; confirmation drawings are issued before production begins.
“Can we order maintenance quantities rather than project volumes?” Coupling fittings usually ship within complete string assemblies where quantities look after themselves, but spares and maintenance orders are welcome, and sensible, since the pins and clips are exactly what a maintenance crew runs short of. Tell us the quantity and we quote honestly, freight arithmetic included.
Complete the String
- Socket eyes – where the connection below needs an eye rather than a clevis jaw
- Ball eyes and ball clevises – the coupling fittings at the structure end
- U shackles (70–170 kN) and yoke plates (100-600 kN) – structure attachment and multi-string arrangements
- Thimble clevises – where wire or strand enters the assembly
- Insulators – the units these fittings couple
- Suspension clamps, strain clamps, preformed tension clamps, armor grip suspension – terminal hardware
- Browse all overhead line fittings and pole line hardware
Get a String-Matched Quote Within 24 Hours
Send your insulator datasheet, string drawing and design rating, or a photograph of the fitting you’re replacing with a rule in frame. Our engineers confirm the coupling designation, the jaw and pin dimensions against the hardware below, and the load class across the whole chain, then return a factory-direct quotation, typically within one working day.
After You Order
Confirmation drawings before production, batch load-test reports and galvanizing certificates with shipment, pins and retaining components packed with the fittings, and assemblies kitted per string so stores issue complete sets rather than loose parts, with engineering support that stays reachable through stringing and beyond.
