Roller chains ANSI ISO
ANSI/ISO roller chains are the most common solution for metallic link power transmission. They comply with ANSI B29.1 (inch series) and ISO 606 (metric series), and are characterized by their standardized pitch, a roller design that reduces friction, and high mechanical efficiency. They are used in industrial machinery, agriculture, conveyor systems, motorcycles, and any application requiring synchronized motion between parallel shafts.
Nomenclature and Components
Section titled “Nomenclature and Components”A roller chain consists of two types of alternating links:
- Inner link: two inner plates joined by bushings on which the rollers rotate. The rollers roll on the sprocket teeth, reducing wear.
- Outer link: two outer plates joined by pins that pass through the bushings of the inner link. The pins bear the main shear stress.
Connecting accessories include the connecting link (master link) with spring clip or cotter pin, and the half link (offset link) that allows length adjustment in half-pitch increments.
Standard Dimensions
Section titled “Standard Dimensions”The numerical values come from ANSI/ISO standards and manufacturers’ technical catalogs. In the tables, all dimensions are given in millimeters and inches, and loads in kN and lbf.
ANSI Series (inch pitch)
Section titled “ANSI Series (inch pitch)”| ANSI Number | Pitch | Roller Diameter | Inner Width | Pin Diameter | Min. Breaking Load | Recommended Working Load* |
|---|---|---|---|---|---|---|
| 25 | 6.35 mm / 1/4“ | 3.30 mm / 0.130“ | 3.18 mm / 0.125“ | 2.31 mm / 0.091“ | 3.5 kN / 780 lbf | 0.53 kN / 120 lbf |
| 35 | 9.53 mm / 3/8“ | 5.08 mm / 0.200“ | 4.78 mm / 0.188“ | 3.58 mm / 0.141“ | 7.8 kN / 1 760 lbf | 1.1 kN / 250 lbf |
| 40 | 12.70 mm / 1/2“ | 7.92 mm / 0.312“ | 7.92 mm / 0.312“ | 3.96 mm / 0.156“ | 13.9 kN / 3 125 lbf | 2.8 kN / 630 lbf |
| 50 | 15.88 mm / 5/8“ | 10.16 mm / 0.400“ | 10.16 mm / 0.400“ | 5.08 mm / 0.200“ | 21.7 kN / 4 880 lbf | 4.3 kN / 970 lbf |
| 60 | 19.05 mm / 3/4“ | 11.91 mm / 0.469“ | 12.70 mm / 0.500“ | 5.94 mm / 0.234“ | 31.3 kN / 7 030 lbf | 6.2 kN / 1 400 lbf |
| 80 | 25.40 mm / 1“ | 15.88 mm / 0.625“ | 15.88 mm / 0.625“ | 7.94 mm / 0.3125“ | 55.6 kN / 12 500 lbf | 11.1 kN / 2 500 lbf |
| 100 | 31.75 mm / 1-1/4“ | 19.05 mm / 0.750“ | 19.05 mm / 0.750“ | 9.53 mm / 0.375“ | 86.7 kN / 19 500 lbf | 17.3 kN / 3 900 lbf |
| 120 | 38.10 mm / 1-1/2“ | 22.23 mm / 0.875“ | 25.40 mm / 1.000“ | 11.11 mm / 0.4375“ | 125.0 kN / 28 100 lbf | 25.0 kN / 5 620 lbf |
- Recommended working load for moderate service with safety factor 5 (approximate). Consult actual application conditions.
ISO Series (metric)
Section titled “ISO Series (metric)”| ISO Number | Pitch | Roller Diameter | Inner Width | Pin Diameter | Min. Breaking Load | Recommended Working Load |
|---|---|---|---|---|---|---|
| 05B | 8.00 mm / 0.315“ | 5.00 mm / 0.197“ | 3.00 mm / 0.118“ | 2.31 mm / 0.091“ | 4.4 kN / 990 lbf | 0.7 kN / 155 lbf |
| 06B | 9.53 mm / 3/8“ | 6.35 mm / 0.250“ | 5.72 mm / 0.225“ | 3.28 mm / 0.129“ | 8.5 kN / 1 910 lbf | 1.4 kN / 315 lbf |
| 08B | 12.70 mm / 1/2“ | 8.51 mm / 0.335“ | 7.75 mm / 0.305“ | 4.45 mm / 0.175“ | 13.8 kN / 3 100 lbf | 3.1 kN / 700 lbf |
| 10B | 15.88 mm / 5/8“ | 10.16 mm / 0.400“ | 9.65 mm / 0.380“ | 5.08 mm / 0.200“ | 22.2 kN / 5 000 lbf | 4.4 kN / 1 000 lbf |
| 12B | 19.05 mm / 3/4“ | 12.07 mm / 0.475“ | 11.68 mm / 0.460“ | 5.72 mm / 0.225“ | 31.1 kN / 7 000 lbf | 6.2 kN / 1 400 lbf |
| 16B | 25.40 mm / 1“ | 15.88 mm / 0.625“ | 17.02 mm / 0.670“ | 8.28 mm / 0.326“ | 55.6 kN / 12 500 lbf | 11.1 kN / 2 500 lbf |
| 20B | 31.75 mm / 1-1/4“ | 19.05 mm / 0.750“ | 19.58 mm / 0.771“ | 10.19 mm / 0.401“ | 84.5 kN / 19 000 lbf | 16.9 kN / 3 800 lbf |
Dimensions correspond to single strand (1 row). For multiple strand chains, loads are approximately multiplied by the number of strands (compensation factor < 1 for dynamic loads).
Load Capacities
Section titled “Load Capacities”Chains are selected based on the power to be transmitted at a given speed. The following table indicates power per strand (single chain) for common ANSI sizes, with proper lubrication and a 19-tooth sprocket.
| ANSI Number | 100 rpm | 500 rpm | 1000 rpm |
|---|---|---|---|
| 40 | 1.5 kW / 2.0 HP | 6.2 kW / 8.3 HP | 9.7 kW / 13.0 HP |
| 50 | 3.2 kW / 4.3 HP | 13.4 kW / 18.0 HP | 20.1 kW / 27.0 HP |
| 60 | 5.6 kW / 7.5 HP | 23.9 kW / 32.0 HP | 35.8 kW / 48.0 HP |
| 80 | 12.3 kW / 16.5 HP | 53.0 kW / 71.0 HP | 79.8 kW / 107.0 HP |
| 100 | 22.8 kW / 30.5 HP | 96.9 kW / 130.0 HP | 145.8 kW / 195.5 HP |
To convert rated power to actual conditions, a service factor correction is applied. The daily working load must not exceed the recommended value in the dimension table; a factor of 1/5 to 1/8 of the minimum breaking load is considered safe depending on the type of service.
Selection Criteria
Section titled “Selection Criteria”The selection of a roller chain follows this procedure:
-
Determine the corrected power: P_corrected = P_motor × f_service
Pcorr = Pmotor · fs
where:
Symbol Quantity Unit Pcorr Corrected power kW (or HP) Pmotor Driving motor power kW (or HP) fs Service factor (dimensionless) – -
In the capacity table, choose a chain number whose rated power (at the high-speed shaft rpm) equals or exceeds P_corrected.
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Verify that the tensile load does not exceed the allowable working load for the chain.
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Select sprockets with the appropriate number of teeth (minimum 17 teeth for general service, 25 teeth for high speed) and a shaft diameter that fits standard hubs.
Typical Service Factors
Section titled “Typical Service Factors”| Application Type | Service Factor (fs) |
|---|---|
| Conveyors, agitators, centrifugal pumps (uniform load) | 1.0 |
| Screw compressors, mixers, general machinery (moderate shock) | 1.2 – 1.4 |
| Crushers, reciprocating presses, rolling mills (heavy shock) | 1.5 – 2.0 |
Mounting and Maintenance
Section titled “Mounting and Maintenance”-
Alignment and Tensioning: Shafts must be perfectly parallel and sprockets aligned. The sag in the slack strand should be 2% to 3% of the center distance. An overly tight chain accelerates pin and bushing wear.
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Lubrication: The lubricant reduces friction between pin and bushing, prevents corrosion, and dampens impacts. The method depends on the linear speed of the chain:
Chain speed (m/s / ft/min) Recommended method < 1.5 m/s / < 295 ft/min Manual or drip lubrication 1.5 – 6 m/s / 295 – 1 180 ft/min Oil bath or splash system > 6 m/s / > 1 180 ft/min Forced lubrication with oil pump Use ISO VG 46 to 220 mineral oils depending on operating temperature.
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Service Life and Replacement: The maximum allowable elongation due to joint wear is 3% for chains with more than 67 pitches and 1.5% for short chains. Measure with specific elongation gauges and replace the chain when this limit is reached.
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Installation of Connecting Links: The spring clip must be installed with its closed end facing the direction of chain travel. For chains with a cotter pin, ensure the pin is fully inserted and the legs are spread.
Selection Tables by Application
Section titled “Selection Tables by Application”| Application | Service | Recommended Series | Service Factor | Remarks |
|---|---|---|---|---|
| Belt conveyor (light load) | Uniform | ANSI 60 / ISO 12B | 1.0 | Low speeds, clean environment |
| Industrial centrifugal pump | Moderate | ANSI 80 / ISO 16B | 1.1 | Precise alignment |
| Motor to gearbox of textile machinery | Moderate | ANSI 40 – 50 | 1.2 | Compatibility with commercial sprockets |
| Bucket elevator (granular materials) | Moderate shock | ANSI 100 / ISO 20B | 1.4 | Double strand chains common |
| Jaw crusher (quarries) | Heavy shock | ANSI 120 / ISO 24B | 1.7 | Check elongation frequently |
| Motorcycle (final drive) | Moderate shock | Series 50 – 60 O‑ring | 1.3 | Sealed chains with rubber seals |
Frequently Asked Questions (FAQ)
Section titled “Frequently Asked Questions (FAQ)”How is the pitch of a roller chain measured?
Section titled “How is the pitch of a roller chain measured?”The pitch is the distance between the centers of two consecutive pins. It is measured with a gauge over several links and divided by the number of pitches to obtain the average value. The nominal pitch matches the ANSI designation (e.g., chain No. 40 → pitch 1/2“ = 12.7 mm) or the ISO digit (08B → 8/16“ = 12.7 mm).
What is the difference between ANSI and ISO series?
Section titled “What is the difference between ANSI and ISO series?”Both standardize pitch, roller, and width dimensions; the ANSI series is expressed in inches and the ISO series in millimeters. However, they are not interchangeable in all cases: ISO 08B and ANSI 40 have the same pitch but different roller diameter and inner width, therefore requiring specific sprockets.
When should I replace a chain due to elongation?
Section titled “When should I replace a chain due to elongation?”The chain must be replaced when the average elongation due to bushing wear reaches 3% (for long chains) or 1.5% (for short chains). Excessive elongation causes improper contact with sprocket teeth, accelerates tooth wear, and can lead to breakage.
What type of lubricant is recommended for roller chains?
Section titled “What type of lubricant is recommended for roller chains?”Mineral or synthetic oils with anti-wear and antioxidant additives are used. Viscosity is chosen according to temperature and speed: in temperate environments (< 40 °C) ISO VG 68 or 100 is common; for high temperatures or low speeds, increase to ISO VG 220. In very dirty environments, PTFE-based spray grease is applied.
What is the typical safety factor for working load?
Section titled “What is the typical safety factor for working load?”The recommended working load is obtained by dividing the minimum breaking load by a factor of 5 for uniform service and up to 8 or 12 for machinery with shocks or frequent reversals. Exceeding these margins drastically reduces service life.
How is a connecting link correctly installed?
Section titled “How is a connecting link correctly installed?”The pins of the connecting link are inserted into the roller ends of the chain, the outer plate is placed, and it is secured with the spring clip. The open end of the clip must point opposite to the chain’s direction of travel. Never weld or hammer the clips, as this damages the surface treatment.