Marine-grade 316L stainless steel shackles from Profab Machine, built for rigging, mooring, and offshore applications where corrosion resistance and documented load ratings are non-negotiable. Available in bow, D/chain, and twisted types with screw-pin or safety-pin closure.
A stainless steel shackle is a U-shaped connector closed by a removable pin, used to link ropes, chains, wire rope, and structural hardware at load-bearing joints. In marine and rigging applications, shackles are the primary interface between anchor chains, mooring lines, sails, deck fittings, and structural pad eyes. The pin design allows the connection to be made or broken without cutting any line.
Galvanised shackles lose their zinc coating in seawater within three to five years. The exposed base steel then corrodes, reducing the actual cross-section below the stamped WLL, with no visible warning before failure. 316L stainless maintains full material dimensions indefinitely in salt water. Its 2–3% molybdenum content raises the Pitting Resistance Equivalent Number (PREN) to ≥ 24, providing the chloride resistance that galvanised hardware cannot match.
Profab supplies four standard shackle configurations in 316 stainless. Each style addresses specific deck layout and loading requirements. Custom profiles are available on request.
Designed with a widened radius to handle unpredictable load directions. Our 316 stainless bow shackles support side loads up to 50% of WLL. Ideal for anchor systems and multi-line connections where pin cross-loading must be avoided.
Engineered for direct chain-to-chain joins and standing rigging. The narrow-profile body ensures maximum strength under fixed-axis loads. Use exclusively for inline tension to prevent WLL reduction from side loading.
Rotates the pin plane 90 degrees to connect perpendicular components, such as turnbuckle jaws to chainplates. This alignment prevents bending loads on the pin, extending the fatigue life of the rigging assembly.
Features a captive bolt-and-nut closure with a cotter pin to prevent loosening under vibration. Standard specification is for marine rigging and mooring use.
WLL values below apply to 316L bow shackles under static axial tensile load, screw pin, at ambient temperature. Industrial shackle design factors typically run 5:1 to 6:1 (MBL to WLL); this table uses 5:1. Side loading and elevated temperature reduce effective capacity. Always verify suitability for your specific loading and governing standard before installation.
| Pin Size (Metric) | Pin Size (Imperial) | WLL (kg) | WLL (lbs) | MBL (kg) | Approx. Weight |
|---|---|---|---|---|---|
| M6 | 1/4″ | 300 | 660 | 1,500 | 35 g |
| M8 | 5/16″ | 500 | 1,100 | 2,500 | 65 g |
| M10 | 3/8″ | 700 | 1,540 | 3,500 | 110 g |
| M12 | 7/16″ | 1,000 | 2,200 | 5,000 | 170 g |
| M14 | 1/2″ | 1,200 | 2,640 | 6,000 | 250 g |
| M16 | 5/8″ | 2,000 | 4,400 | 10,000 | 420 g |
| M20 | 3/4″ | 3,200 | 7,040 | 16,000 | 750 g |
| M24 | 1″ | 4,750 | 10,450 | 23,750 | 1.4 kg |
| M30 | 1-1/4″ | 8,500 | 18,700 | 42,500 | 3.2 kg |
| M36 | 1-1/2″ | 12,000 | 26,400 | 60,000 | 6.0 kg |
| M40 | — | 17,000 | 37,400 | 85,000 | 9.5 kg |
| M52 | 2″ | 25,000 | 55,000 | 125,000 | 22 kg |
Standard grade for indoor machinery, automation, and dry or mildly humid environments. Good resistance to cleaning chemicals. Cost-effective for high-volume orders. Not suitable for continuous salt spray or chloride-heavy process environments.
Food Automation IndoorMarine and food-grade standard. 2–3% molybdenum addition raises chloride pitting resistance significantly above 304. Required for outdoor, marine, offshore, and food equipment with CIP chemical cleaning.
Marine Chemical PumpsPrecipitation-hardened martensitic grade. Tensile strength of at least 1,310 MPa in H900 condition, significantly stronger than 316 at equivalent cross-section. Specified for high-load pins and fittings in motorsport, aerospace, and high-cycle fatigue applications where load rating is the primary constraint.
Aerospace Motorsport Hi-LoadApproximately 30% higher yield strength than 316L at equivalent cross-section, enabling a smaller, lighter shackle at the same WLL. PREN of 34–36 versus 316L's ≥ 24 provides superior resistance to stress-corrosion cracking in warm tropical seawater and subsea environments. Custom-sourced, available M10–M40 on request.
Offshore Subsea TropicalEach shackle body and pin starts as solid round 316L bar, saw-cut to length. CNC turning shapes the bow or D profile and bores the pin holes to precise tolerance, and CNC milling cuts the flat faces and threads the pin bore. Machining from solid bar holds tighter dimensional control on pin fit and WLL consistency across a production run than casting allows.
D shackles on shroud-to-chainplate connections and bow shackles on forestay attachment. Twisted shackles at chainplate-to-turnbuckle junctions where perpendicular geometry would otherwise create pin-bending moments. 316L body is required for any standing rigging on salt-water vessels.
Bow shackles join anchor chain to anchor crown and swivel at both ends. Safety-pin variants are specified for permanent mooring buoy chains that are not regularly inspected, since the bolt-and-nut pin cannot rotate loose under cyclic wave loading.
Duplex 2205 shackles for platform mooring lines, riser hang-off points, and ROV umbilical connections where 316L stress-corrosion cracking resistance is marginal at operating temperatures.
Safety-pin bow shackles for cargo lashing, deck-mounted pad eye connections, and container handling equipment on commercial vessels and ro-ro ferries.
316L bow shackles for net hauling, trawl gear connections, and aquaculture cage mooring systems. Stainless maintains full cross-section over its service life in seawater, eliminating the 3 to 5 year replacement cycle required with galvanised hardware.
Lightweight M6–M12 316L shackles for kite-surfing harnesses, wakeboard tower connections, and coast-guard rescue equipment where both corrosion resistance and minimum weight are simultaneously required.
Every shackle body and pin is machined from certified 316L stock, so the molybdenum content that gives this grade its chloride resistance doesn't vary batch to batch. The grade you specify is the grade you receive.
Bow, D, twisted, and safety pin shackles are machined to the same WLL specification across the full M6 to M52 pin range, so a complete rigging inventory can be sourced from one supplier instead of matching parts across brands.
Duplex 2205 and non-standard pin sizes are machined to your drawing rather than limited to catalogue increments, for offshore and subsea specifications that fall outside the standard 316L range.
Not seeing your question? Email us at [email protected] and we typically reply same day.
A bow (anchor) shackle has a rounded, wider bow that allows side loading and can accept multiple lines simultaneously. A D (chain) shackle has a straight, narrow body designed exclusively for inline tension, no more than one component per end, zero side load. Side-loading a D shackle at just 45 degrees can reduce effective load capacity by around 30% of the rated WLL. When the load direction can vary or multiple lines share one point, always specify a bow shackle.
Standard shackles are supplied for marine rigging and mooring use. Overhead lifting applications typically require additional certification and testing beyond the standard specification.
Yes, Duplex 2205 shackles are available in M10–M40 on enquiry. Specify Duplex when you need a smaller, lighter shackle at the same WLL as a 316L version, since Duplex 2205 has approximately 30% higher yield strength at equivalent cross-section. Also specify Duplex for subsea, tropical seawater above 25°C, or any application where stress-corrosion cracking in austenitic 316L is a documented concern. Duplex 2205 carries a PREN of 34–36 versus 316L's ≥ 24.
Provide your required parameters, including shackle type, pin size, stainless steel grade, and quantity.
We will work on the best solution based on your request and send you a specific quote within 24 hours.
30 days standard. Samples before full production run on new custom parts. QC report before shipment.
Sea, air, or express courier. Material certs and inspection report inside every box.
Installing with wire rope or chain? Cotter pins and seizing wire are commonly used to secure a screw-pin shackle against vibration, so mention your requirements when you request a quote.
If you already have the drawings, please send email to [email protected] directly for an instant quote.
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