Stainless Steel Rigging Thimbles
Rigging thimbles are entirely different than the sewing thimbles you might be familiar with, and they serve an entirely different purpose. This type of thimble is available in several materials such as stainless steel, aluminum, bronze, and strong plastics like acetal. In this article we will focus on stainless steel thimbles are they are some of the most effective and most common.
WHAT ARE RIGGING THIMBLES?A rigging thimble is typically used to protect or strengthen the termination of a line or wire. When the line ends with an eye splice or loop, a thimble can help strengthen the loop, protect the inside of the loop from abrasion, and help the loop retain its shape under load. A stainless steel thimble will provide a hard and durable surface around the inside of the eye splice or loop.
When specifying a stainless steel thimble, there are a few important factors to consider. Depending on the environment, a different grade of stainless may be required. Grade 316 thimbles will be more expensive than some commodity grade stainless thimbles, but they provide excellent corrosion resistance and are necessary in corrosive environments like a marine or saltwater application.
Another factor to consider is how the type and quality of thimble relates to the intended application and rope material it will be used with. Wire rope thimbles can sometimes have sharp edges, making them ill-suited for use with a fiber rope. If a thimble with sharp edges moves or shifts within the splice of a fiber rope, it can increase abrasion, damage, or even cut the rope. Any fiber rope will stretch under load, increasing the chances of a thimble loosening or shifting slightly from its original position.
Typically, a high quality stainless steel thimble will have fewer rough burrs or sharp edges than a cheap thimble. However, if this is a concern in a fiber rope application, one option to consider is a sailmaker’s thimble. A sailmaker’s thimble has a rounder profile with no sharp edges that can damage a rope or sail. Although the rounder and wider shape can make them slightly more difficult to properly install, they are a safe and popular choice for these applications.
Where are Thimbles used?
Thimbles are commonplace not only in marine rigging but industrial applications as well. Most cables, wire ropes, and rope slings that terminate in a loop can benefit from the use of a thimble, resulting in applications across a wide range of industries.
Thimbles come in different shapes and sizes proportional to the rope or wire diameter and intended purpose. The groove around the outside of the thimble must be an appropriate size for the rope or wire to lay in, as an improper fit will cause the thimble to be either ineffective or not remain in place. A light duty thimble will have less side coverage, primarily lining the inside of the loop and intended for abrasion resistance and low loads. Alternatively, a heavy duty thimble intended to bear higher loads will often have a groove deep enough to wrap around and protect more of the rope or cable while also being strong enough to withstand a much higher load than a lower profile light duty thimble.
For more information, check out Ronstan Industrial’s range of stainless steel thimbles and sailmaker’s thimbles or feel free to contact us directly.