Alloy Clevis Slip Hooks

In the specialized world of chain rigging, the geometric design of the hook dictates the function of the entire assembly. While Grab Hooks are engineered with a narrow throat to lock onto a chain link and shorten the leg, Slip Hooks are designed with a wide, rounded throat that allows the chain to slide freely through the hook bowl. This distinct "sliding" capability makes the Slip Hook the primary hardware solution for creating choker hitches, where the sling must cinch tightly around a load to secure it through friction and tension.

Alloy Clevis Slip Hooks

Holloway Houston stocks the Crosby A-331 Alloy Clevis Slip Hook, universally recognized as the gold standard for Grade 80 and Grade 100 chain assemblies. Forged from high-performance Quenched and Tempered alloy steel, these hooks provide the extreme ductility and tensile strength required for critical overhead lifting, heavy transport towing, and industrial utility applications.

The Clevis Connection: Streamlined Efficiency

One of the defining features of the A-331 series is the Clevis connection point. In traditional rigging, connecting a hook with an "eye" (a closed loop) to a chain requires an intermediate component called a connecting link (often referred to as a Hammerlok or coupling link). This adds weight, cost, and an additional failure point to the sling.

The Clevis Slip Hook eliminates this "middleman." It features a U-shaped clevis fitting with a built-in alloy load pin and a retaining cotter pin. This design allows the hook to attach directly to the chain link.

Reduced Weight : By removing the coupling link, the sling becomes lighter and easier for riggers to handle in the field.
Minimized Length : The direct connection reduces the overall headspace required, which is critical in low-clearance lifting scenarios.
Fail-Safe Security : The retaining pin is strictly for securing the load pin; it does not bear the load itself, ensuring the structural integrity of the connection relies solely on the robust alloy load pin.

Choker Hitches and Load Control

The primary operational advantage of a Slip Hook is its ability to form a Choker Hitch. In this configuration, the sling is passed around the load (such as a bundle of pipes, a steel I-beam, or a log), and the hook is clipped back onto the chain body. Because the chain can slide through the hook's bowl, lifting the assembly causes the loop to tighten, gripping the load securely.

Technical Note on Choking: Riggers must be aware that using a sling in a choker hitch reduces the Working Load Limit (WLL) of the sling. While the hook itself retains its rated capacity, the sling efficiency is typically reduced to 80% of its vertical rating due to the angle of choke. The smooth, rounded design of the Crosby A-331 is engineered to minimize damage to the chain links as they slide, ensuring the hitch tightens smoothly without binding or gouging the steel.

The Crosby Metallurgy Advantage

In the rigging industry, steel quality is not just a specification; it is a safety feature. HHI chooses Crosby because of their proprietary heat-treatment process.

Quenched & Tempered (Q&T) : The A-331 hooks are not just forged; they are Quenched and Tempered. This process aligns the grain structure of the alloy steel to maximize ductility.
The Visual Warning : If a generic, cheaper hook is overloaded, it often snaps suddenly (brittle failure). A Crosby Q&T hook is designed to yield and deform under overload. The throat opening will noticeably widen, or the hook will straighten out, providing a clear visual warning to the rigger that the hardware is compromised and must be retired. This "fail-slow" characteristic saves lives.

Applications: Lifting vs. Towing

Slip hooks are versatile tools found across multiple sectors, but their specific configuration varies by use case.

1. Overhead Lifting (ASME B30.10) When used for overhead lifting in construction or manufacturing, Slip Hooks generally require a Safety Latch. The latch bridges the throat opening to prevent the chain from accidentally slipping out if the load sets down and the line goes slack. The Crosby A-331 features a pre-drilled cam to accept the heavy-duty S-4320 Latch Kit.

2. Towing and Dragging In the transport, recovery, and logging industries, Slip Hooks are often used without latches to allow for rapid disconnection. They are the standard termination for heavy-duty tow chains and binder chains, allowing operators to quickly loop a chain around a vehicle axle or recovery point.

Capacity Range & Specifications

Holloway Houston stocks A-331 hooks to match every standard chain size in the industry. The Working Load Limit (WLL) of the hook is matched to the Grade 80/100 chain it attaches to.

1/4" & 5/16" (Utility) : WLLs of 2,750 lbs and 4,300 lbs. Ideal for light equipment tie-downs and small chain slings.
3/8" & 1/2" (Industrial) : WLLs of 5,250 lbs and 9,000 lbs. The standard sizes for general construction rigging and machinery moving.
5/8" & 3/4" (Heavy Lift) : WLLs of 13,500 lbs and 19,250 lbs. Designed for heavy steel coil handling, marine applications, and large-scale recovery.

Inspection and Maintenance

Like all rigging hardware, Slip Hooks must be inspected regularly. Under ASME B30.10, a hook should be removed from service if :

Throat Widening : The throat opening has increased by more than 5% (indicating overload).
Twisting : The hook tip is twisted more than 10 degrees out of plane from the hook body.
Wear : There is wear exceeding 10% of the original dimension in the bowl or saddle.
Clevis Damage : The load pin shows signs of bending or the cotter pin is missing.

Complete Your Rigging Assembly

A Slip Hook is the termination point of a system. To build a safe and compliant sling, pair these hooks with Grade 80 or Grade 100 Alloy Chain. If your application requires the chain to be locked in place rather than sliding, please visit our Grab Hooks category. For overhead lifting compliance, ensure you add the compatible Crosby Safety Latch Kit to your order.