Shackle Types Explained: Anchor vs. Chain & Screw Pin vs. Bolt Type Guide

Shackles are a critical connection component in lifting and rigging systems. They link slings, chains, wire rope, and hardware to the load, and their selection directly affects load alignment, force distribution, and connection stability during a lift.

Two primary factors define shackle selection : body area and pin configuration. Body shape determines how sling legs and fittings seat within the shackle, while pin type affects how the connection is secured and how it performs under vibration, cyclic loading, or extended service.

This article explains the practical differences between anchor (bow) and chain (D) shackles, and compares screw pin, round pin, and bolt type configurations. The focus is on product behavior and application so rigging personnel can match shackle types to real-world lifting conditions.

Disclaimer – Awareness Only

This content provides general awareness on shackle selection. It does not replace manufacturer instructions, engineered lift plans, or company procedures. All lifting operations must follow the applicable manufacturer’s data and ASME B30.26.

Anchor Shackles vs. Chain Shackles

The most visible difference between shackle types is body area. Area controls how forces enter the shackle and how many components can connect at one point.

Anchor Shackles (Bow Shackles)

Anchor shackles feature a rounded bow with a larger internal width. This shape allows multiple sling legs, links, or fittings to sit side by side without crowding the pin or forcing components out of alignment.

Key characteristics :

• Rounded bow with increased internal clearance.
• Supports multiple sling legs or fittings.
• Allows limited angular movement within manufacturer limits.
• Commonly used at load connection points.

Typical applications :

• Multi-leg chain or wire rope slings.
• Connections involving master links or quad assemblies.
• Lifts where slight changes in sling angle occur during positioning

Anchor shackles are commonly selected when two or more components must gather into a single connection point. Their area helps distribute load more evenly and reduces the risk of pin bending caused by stacked hardware.

Chain Shackles (D Shackles)

Chain shackles have a narrow, straight-sided body that keeps the load path closely aligned with the pin and legs.

Key characteristics :

• Narrow internal width.
• Straight legs designed for in-line loading.
• Compact profile.

Typical applications :

• Single-leg chain terminations.
• Straight-line pulls.
• In-line connections to pad eyes or fixed attachment points.

Chain shackles are intended for straight-line tension only. Their narrow area does not provide clearance for multiple sling legs or accommodate angle changes.

Anchor vs. Chain Shackles — Comparison

If the rigging area requires gathering multiple components or tolerating angle changes, anchor shackles are typically selected.

Pin Configurations Explained

While the body area controls load path, the pin configuration determines how the shackle is secured and how it performs over time.

Screw Pin Shackles

Screw pin shackles use a threaded pin that engages directly into one ear.

Characteristics :

• Quick installation and removal.
• No separate nut or cotter pin.
• Common in temporary or frequently adjusted rigging.

Typical uses :

• Day-to-day crane picks.
• Equipment relocation.
• Short-term lifts assembled and removed under supervision.

Because screw pins rely on thread engagement alone, they are commonly used where connections are monitored and regularly disassembled. In applications involving vibration or load cycling, additional pin security may be required.

Round Pin Shackles

Round pin shackles use a smooth pin secured with a cotter pin.

Characteristics :

• Simple pin retention.
• Limited resistance to bending.
• Restricted to controlled loading conditions.

Typical uses :

• Straight-line, in-line loading.
• Static or monitored connections.
• Tie-down or non-adjusting applications.

Round pin shackles are not intended for side loading or for collecting multiple sling legs. Many lifting programs restrict their use for overhead lifting.

Bolt Type Shackles (Safety Bolt Shackles)

Bolt type shackles use a bolt passing through both ears, secured with a nut and a secondary retaining device.

Characteristics :

• Secondary retention prevents pin rotation.
• Performs better under vibration and cyclic loading.
• Preferred for long-term or semi-permanent connections.

Typical uses :

• Pad eyes.
• Lifting beams and spreader bars.
• Engineered lifting points.

Bolt type shackles are commonly specified where the connection remains installed for extended periods or where inspection access is limited.

Side Loading and Shackle Area

Shackles achieve maximum capacity when loaded in line. Side loading introduces bending and uneven force distribution, reducing capacity.

• Anchor shackles may be side loaded within manufacturer limits and with capacity reduction.
• Chain shackles are not intended for side loading.

Example reduction pattern (for awareness only) :

• 0°–5° from in-line: 100% of rated WLL.
• Up to 45°: approximately 70% of rated WLL.
• Up to 90°: approximately 50% of rated WLL.

Actual reduction values vary by manufacturer and product series. Always refer to the current reduction chart for the specific shackle in use.

When side loading cannot be avoided, the rigging arrangement should be reviewed to determine whether area changes or engineered solutions are required.

Matching Shackles to Sling Types and Applications

Multi-Leg Chain and Wire Rope Slings

Anchor shackles are commonly used where multiple legs connect to one point. Bolt type anchor shackles are often selected when the connection remains in place or inspection access is limited.

Single-Leg and Straight-Line Pulls

Chain shackles provide a compact, aligned connection for straight-line loading. Screw pin versions are commonly used for temporary connections, while bolt type configurations are preferred where vibration is present.

Synthetic Slings

Synthetic slings benefit from larger bearing radii. Anchor or wide-body shackles help spread load across the sling eye and reduce localized compression.

Long-Term and Engineered Attachments

Bolt type anchor shackles are commonly specified for lifting beams, pad eyes, and engineered systems where the shackle remains installed for extended periods.

Practical Selection Checklist

When selecting shackles, consider :

• Body area : Anchor vs. chain.
• Pin type : Screw pin, round pin, or bolt type.
• Loading direction : In-line vs. angled.
• Connection duration : Temporary vs. long-term.
• Operating environment : Vibration, temperature, and inspection access.

This checklist supports product selection awareness but does not replace manufacturer data or engineered lift plans.

Frequently Asked Questions

Are anchor shackles stronger than chain shackles?

Both are rated with a working load limit. The difference is area, not inherent strength.

Can a chain shackle be used for multi-leg connections?

Chain shackles are intended for in-line loading. Anchor shackles are typically used for multi-leg connections.

When should bolt type shackles be used instead of screw pins?

Bolt type shackles are preferred for long-term installations or vibration-prone service.

Are round pin shackles acceptable for lifting?

They are rated for straight-line loading but are often restricted in overhead lifting programs.

Can a shackle be side loaded if capacity is reduced?

Only anchor shackles may be side loaded within manufacturer limits. Chain shackles are not intended for side loading.