6061-T6: an aluminum alloy that has excellent corrosion resistance to air and salt water. It is an easily welded, tough alloy that responds well to anodizing.

7075-T6: the strongest of the aluminum alloys with strength comparable to many steels. Harken uses 7075-T6 in its hydraulic cylinders for applications where weight is critical. A vigorous maintenance schedule is required when using this alloy, because corrosion resistance is lower than 6061-T6. Available in hardcoat or clear-anodized finishes.

Bearing properties are functions of contact area, material type, bearing cages, and whether the bearing rolls or slides.

Bearing Types

Ball bearings: very low-friction; low/medium-load capacity.

Roller bearings: low-friction; high-load capacity.

Sleeve bearings: medium/high-friction; extremely high-load capacity.

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Bearing Materials

Stainless steel is stronger than Torlon® thermoplastic and Torlon is stronger than Delrin® acetal resin. Because stainless is heavier and usually higher maintenance, Torlon is used in most high-load applications.

Contact Area

More contact between the bearing and the race increases friction, but also increases load capacity. Balls are loaded on small points, cylindrical rollers are loaded along their length, and sleeve bearings are curved around the shaft so a large portion is in contact. Unlike balls and cylinders, sleeves are not prone to being flattened by extreme or static loads because they already conform to the curvature of the shaft.

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Motion (rolling, caged rolling, or sliding) 

Sliding bearings (known as sleeve, plain, full-contact, bushing, or journal bearings) are very high strength but have nothing to reduce friction between contact areas. At most, they have a low-friction sleeve between the surfaces. Rollers and balls avoid almost all of this friction because they do not slide against the race, though they can come in contact with each other. Caged roller bearings are separated from each other to avoid this.

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A becket is closed bail on a block that may or may not open. It usually serves as a deadend within a purchase.

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Caged Bearings

Caged bearings are roller bearings held in a cage that keeps them separated from each other and parallel to reduce friction. Caged bearings are used in winches and Black Magic® pulleys.

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Captive Bearings

Captive bearings are ball bearings that are contained so they won’t spill during product maintenance. Black Magic blocks have ball bearings held captive by the lip of the sheave. CB traveler cars feature ball bearings held captive by a wire guide.

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Carbo® Air pulleys feature lightweight, fiber-reinforced, nylon-resin sideplates with a 60% higher MRL than stainless-reinforced Classic pulleys. Lightweight fiber-reinforced Carbo-Cams are ideal for applications where weight is critical. The Carbo name comes from an additive that gives pulleys their color and UV-resistance.

Carbon Black

Carbon black is a color additive used in black Delrin® ball bearings, pulley sheaves, and sideplates to protect against UV exposure.


The Classic line for low to moderate loads is based on Harken’s founding designs. They are typically stainless and stainless-reinforced Delrin. Many but not all Classics have stronger and lighter counterparts in the Carbo line.


Clear aluminum anodizing is an electrochemical process that produces a corrosion-resistant finish. It also hardens the surface, making components less prone to scratches and dents. It is “clear” because the protective layer isn’t thick enough to change the color of the component (though dye can be added). More rigorous anodization, such as hardcoat, can give components a black or colored hue.

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Delrin® Acetal Resin

Black material which excels in low to moderate-load applications. Delrin acetal resin is used for bearings, sheaves, and sideplates in smaller pulleys.


Hardcoat aluminum anodizing is an electrochemical process that produces a corrosion-resistant finish with hardness characteristics second only to diamonds. Harken’s hardcoating process is twice as thick as black anodizing to provide extra protection against scratches, dents, superficial deformation, and corrosion.

anodizing table_dec15

Hard Lube Anodizing

Hard Lube-anodized aluminum includes all the corrosion-resistant properties of hardcoat-anodized aluminum with the additional benefits of a PTFE coating for a smoother surface and reduced friction.

High-Beam Rail 

High-beam rail has a taller profile than low-beam rail. Use high-beam rail in carriage systems that span unsupported areas with the rail.

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Maximum Rated Load (MRL)

Never, under any circumstances, exceed the capacity or maximum rated load (MRL) of any piece of equipment. The maximum rated load may be found in our catalog, on our website, or through our technical service department. Loads above the MRL can cause the equipment to fail suddenly and unexpectedly.

Maximum rated loads are a coefficient ratio of the breaking load. Human suspension applications require a 10:1 ratio.You must carefully read, understand, and follow all of the warnings and instructions in the User Manual provided by Harken in order to avoid an accident.

Nylatron® Nylon

Durable, lightweight composite material that has high mechanical strength and stiffness, resists static electricity, and has excellent wear resistance.

Pinstop Trolleys

Pinstop trolleys have a lever that is used to control the range of movement or lock trolleys in position along the rail. Open the pinstop to move; close to lock in place.

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PTFE-coating, along with anodizing, protects aluminum against corrosion by sealing the surface from moisture. It also minimizes friction and gives the component better wear resistance.


A ratchet is a mechanism that holds part of the load on a pulley, letting you pull and release with complete control. Ratchets make it much easier to hand-hold higher loads by only allowing the sheave to turn in the one direction. This reduces muscle fatigue and offers better control when easing the line.

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Roller Bearings

Roller bearings have greatly increased bearing contact surface area over ball bearings. This increases the strength and load capacity, but can also increase friction. For the best combination of high-strength and low-friction hardware, we use caged roller bearings.

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Self-tailing Jaws

A self-tailing winch allows the rope to be automatically and properly pulled and paid out. The “jaws” are a facing pair of clamping rings at the top of the winch drum with an angular shaped groove between them for the rope. The self-tailing jaws support a stripper arm for feeding the rope from the drum to the groove and paying out rope from the groove.

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A U-shaped bracket, the open end of which is closed by a removable bolt (shackle pin), used for securing lines, chains, etc.

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A sheave (pronounced “shiv”) is the wheel of a pulley with a groove along its edge for holding a line or cable.

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Sideplates are the outer faces of a pulley that hold the sheave (wheel) in place. Sideplates can be made of lightweight composites, hardcoat-anodized aluminum, stainless steel, or titanium depending on the load requirements of the application.

Sleeve Bearings

Sleeve bearings (also known as full-contact, plain, bushing, friction bearings, or journal bearings), are cylindrical inserts that provide a low-friction layer for two surfaces to slide against each other, such as a pulley sheave turning on a journal. Sleeve bearings are excellent for very high loads as they distribute the load over a large surface. For lower loads, roller bearings or ball bearings are preferred because bearings that roll have significantly less friction than bearings that slide.

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Stainless Steel

17-4 PH Stainless Steel: this alloy is used in gears because it is hardenable to extremely high strengths. 17-4 PH is more corrosion-resistant than any other standard hardenable stainless steel.

316 Stainless Steel: this is a nonhardenable alloy with high corrosion resistance in freshwater and saltwater.

XM-19 Stainless Steel: this stainless is highly alloyed, with very high mechanical strength and superior corrosion resistance. Rods and pins in Harken hydraulic cylinders are made of XM-19 stainless.

Static Loads

Light to heavy loads that do not require frequent adjustment. Constant stress deforms certain materials, so strength takes priority over friction reduction in equipment designed for static loads.

Stripper Arm (also called self-tailing arm)

The stripper arm peels the top wrap of line off the winch drum as it is turning so it does not bunch up at the top. Winches without these require two-handed or two-person operation to manually strip the line while turning it.

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Soft Attachment

A term encompassing lashings, loop lashings, and any other fiber-based equipment that replaces the function of a shackle or padeye. They offer incredible weight savings over traditional shackles and padeyes made with stainless steel. However, they are prone to wear and should only be used on regularly maintained systems.

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This lightweight, hard metal has the highest strength-to-weight ratio of any metal. Its corrosion rate is so low that after 4000 years in seawater, corrosion would only have penetrated to the thickness of a thin sheet of paper. Harken uses titanium rollers in TTR2 pulleys to handle bearing loads.

Torlon® Thermoplastic

Exceptionally strong crush/impact-resistant bearing material that withstands heavy long-term use and shock loading. Most Harken hardware that sees extreme loads uses greenish-brown Torlon® bearings.

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UV light photo-degrades composites by breaking their chemical bonds, leaving them weak, brittle, and discolored. This is common in equipment with white bearings. All Harken composites and bearings are naturally UV-resistant or use stabilizers like carbon black.

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Wire Block

Wire blocks are ideal for wires as well as lines used in high-load rigging applications. They have aluminum sheaves to stand up to the extreme loads and abrasive materials. Some wire pulleys use stronger bearing materials and configurations.

Delrin® is a registered trademark of E. I. du Pont de Nemours and Company or its affiliates.
Nylatron is a registered trademark of Quadrant EPP USA Inc.
Torlon® is a registered trademark of Solvay Advanced Polymers.