ANSI Numbers: Pitch and Strand Count
In ANSI designations, the first digits relate to pitch. The number is not a direct measurement; it is a code based on eighths of an inch. A 40 chain has a 1/2 in (12.70 mm) pitch. A 50 chain is 5/8 in, 60 is 3/4 in, and 80 is 1 in. The suffix -1, -2, or -3 indicates simplex, duplex, or triplex. ANSI 40 also has defined roller diameter (7.94 mm), inner width (7.94 mm), pin diameter, and minimum tensile strength. Tensile strength changes with material and heat treatment, so the number alone is not a load rating.
ANSI Table Walkthrough: 25, 35, 40, 50, 60, 80, 100
| ANSI | Pitch (mm) | Roller dia. mm | Inner width mm | Pin dia. mm | Min. tensile kN* |
|---|---|---|---|---|---|
| 25 | 6.35 | 3.30 | 3.18 | 2.30 | 3.5 |
| 35 | 9.525 | 5.08 | 4.76 | 3.58 | 7.9 |
| 40 | 12.70 | 7.92 | 7.85 | 3.96 | 13.9 |
| 50 | 15.875 | 10.16 | 9.40 | 5.08 | 21.7 |
| 60 | 19.05 | 11.91 | 12.57 | 5.95 | 31.3 |
| 80 | 25.40 | 15.88 | 15.75 | 7.92 | 55.6 |
| 100 | 31.75 | 19.05 | 18.90 | 9.53 | 86.9 |
*Minimum ultimate tensile strength per ANSI/ASME B29.1 (single strand) — breaking load, not working load. ANSI 25 and 35 are rollerless (bushing) chains; the diameter shown is the bushing OD. Verify with the manufacturer for the actual chain.
Read the table by pitch first. ANSI 25 is 1/4 in pitch, 35 is 3/8 in, 40 is 4/8 in, 50 is 5/8 in, 60 is 6/8 in, 80 is 8/8 in, and 100 is 10/8 in. ANSI 25 and 35 are used in small drives, office equipment, and light conveyors. They are more sensitive to misalignment and lubrication because pin and bushing sizes are small (these two sizes have no rollers). ANSI 40 and 50 are common in drives and conveyors. ANSI 60 and 80 are used where higher torque and larger shock loads occur. ANSI 100 is found in heavier conveyors and industrial drives. The pin diameter and plate thickness affect tensile strength, fatigue life, and wear. A 40 chain from one supplier may have a higher minimum tensile than another because of material, heat treatment, and plate design.
ISO/DIN B-Series and Comparison to ANSI
ISO/DIN designations also encode pitch: in 08B-1, 08 is the pitch code in sixteenths of an inch (08 × 1/16 in = 1/2 in = 12.70 mm), B indicates European B series, and -1 means simplex. The B series is common in Europe and in equipment built to ISO/DIN standards. It is not the same as ANSI, even when pitch matches. 08B roller diameter is 8.51 mm and inner width 7.75 mm, while ANSI 40 has 7.92 mm roller and 7.85 mm inner width. These differences affect sprocket fit. ANSI 40 and 08B are not normally interchangeable without checking sprockets.
| DIN B | Pitch mm | Roller dia. mm | Inner width mm | Pin dia. mm | Min. tensile kN* | Nearest ANSI | Fit note |
|---|---|---|---|---|---|---|---|
| 08B | 12.70 | 8.51 | 7.75 | 4.45 | 17.8 | 40 | Not direct interchange |
| 10B | 15.875 | 10.16 | 9.65 | 5.08 | 22.2 | 50 | Check sprocket |
| 12B | 19.05 | 12.07 | 11.68 | 5.72 | 28.9 | 60 | Check sprocket |
| 16B | 25.40 | 15.88 | 17.02 | 8.28 | 60.0 | 80 | Check sprocket |
| 20B | 31.75 | 19.05 | 19.56 | 10.19 | 95.0 | 100 | Check sprocket |
*Minimum ultimate tensile strength per ISO 606 / DIN 8187 (single strand). ISO/DIN has A and B series. A series is often closer to ANSI in some sizes, but still verify dimensions. A-series and B-series sprockets are also different. A 08A chain may look close to 08B, but roller diameter, inner width, and tooth space can differ. When a machine was built in Europe, the replacement should usually follow the original DIN/ISO series unless the sprockets are changed as a set.
Strand Count and Tensile Scaling
The suffix on ANSI and ISO/DIN chain indicates strand count: -1 simplex, -2 duplex, -3 triplex. A 40-2 chain is a duplex 40 chain. A 08B-3 is a triplex 08B chain. More strands increase width, pin length, and load capacity. Minimum tensile strength for multi-strand chain is often roughly proportional to strand count in catalogs: 40-2 is about twice 40-1, 40-3 about three times. Do not use that as a working load rule. Load sharing between strands depends on sprocket alignment, pin fit, plate stiffness, lubrication, and wear. The working load should be based on the manufacturer’s rating, the application service factor, and the drive design. A duplex chain also needs a duplex sprocket with the correct strand spacing.
Sprocket Matching Rules
Match the chain standard to the sprocket standard. For ANSI chain, use an ANSI sprocket. For DIN B chain, use a DIN B sprocket. Check pitch, roller diameter, inner width, and number of teeth. The tooth space and roller seat must match the chain. A sprocket cut for ANSI 40 may not seat an 08B chain correctly because roller diameter and inner width differ. For multi-strand chain, match the strand count and strand spacing. Check bore, keyway, setscrew, hub diameter, and maximum bore. Confirm the sprocket is not worn: a worn sprocket will damage a new chain. Align shafts and sprockets before tensioning. For high-speed drives, check balance and tooth profile. For corrosive environments, use stainless 304/316 chain and compatible sprockets where needed. Check center distance and chain length together. If the center distance is fixed, the chain length must often be an even number of pitches, and a half link should be used only when the design allows it. Confirm lubrication method: manual, drip, bath, or oil stream. The sprocket material and hardness should suit the load and environment.
Common Ordering Mistakes
1. Ordering by chain number only. ANSI 40 and 08B share pitch but are not direct replacements. The roller diameter and inner width differ.
2. Forgetting strand count. A 40-1 will not replace a 40-2. The width and sprocket requirement change.
3. Ignoring sprocket compatibility. Replacing chain on a worn or mismatched sprocket causes rapid wear and noise.
4. Confusing minimum tensile with working load. Minimum tensile is a breaking value, not a safe operating load. Apply a service factor.
5. Leaving out application details. Lubrication, temperature, corrosion, shock load, chain length, connecting link type, and attachments all affect selection.
FAQ
Is ANSI 40 the same as 08B? No. They have the same nominal pitch, but roller diameter, inner width, pin diameter, and tensile strength differ. Use matching sprockets and verify dimensions.
What does -2 mean on a roller chain? It means duplex, or two strands. A -1 is simplex, -3 is triplex. Multi-strand chain requires a matching multi-strand sprocket. The strand spacing is standardized, but check the sprocket drawing.
Can I use an ANSI chain on a DIN sprocket? Not normally. Even with the same pitch, the roller diameter and tooth space may not match. Check the standard and dimensions first.
How do I choose chain size? Start with pitch, roller diameter, inner width, strand count, and tensile requirement. Then check sprocket fit, speed, load, environment, and lubrication. Select by dimensions and working conditions, not chain number alone.
What to Check Before Ordering
Confirm standard, chain number, series, strands, pitch, roller diameter, inner width, pin diameter, and tensile strength. For corrosive environments use stainless 304/316. Escalator chains need precise pitch. Forklift lifting uses leaf chains BL/LL series. Scraper conveyors use forged chains. Custom chains can be made from drawings; MOQ can start from 1 meter. If the chain is for a critical drive, request a dimensional drawing and tensile certificate. For custom attachments, provide pitch, roller diameter, inner width, pin diameter, attachment spacing, and side plate details. Select by dimensions and working conditions, not chain number alone.