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When a slipping or mismatched sprocket brings your project to a halt, you need a drop-in replacement that fits right the first time. Makers, robotics builders, and light-industrial DIYers who work with 04C roller chain systems demand dimensional accuracy and consistent tooth geometry — and that is exactly what this 04C chain drive sprocket delivers across every tooth count and bore size in the range.
Each sprocket is machined from 45# medium-carbon steel, offering a balance of hardness and machinability suited to chain drive applications. The 04C pitch (6.35 mm / 0.25 in) matches standard 04C roller chain. Tooth counts span 9 T through 40 T, and bore diameters range from 5 mm (approx. 0.197 in) up to 20 mm (approx. 0.787 in), including keyed-bore variants for positive shaft engagement. Matching 04C roller chain (sold by the 0.5 m or 5 m length) and both closed-loop and extension chain connectors are available as variant options on this same listing.
Typical use cases include small conveyor drives for DIY automation rigs, gear-reduction stages in electric go-kart and e-bike projects, and replacement sprockets for light agricultural or workshop equipment running 04C chain. Long-tail searches such as "04C sprocket 20 tooth 8mm bore", "45 steel chain sprocket replacement", and "04C roller chain drive kit" all point to this versatile component family.
| Chain Standard | 04C (ISO/DIN) |
|---|---|
| Chain Pitch | 6.35 mm (0.25 in) |
| Material | 45# medium-carbon steel |
| Tooth Count Range | 9 T, 10 T, 11 T, 12 T, 15 T, 16 T, 17 T, 20 T, 24 T, 25 T, 30 T, 35 T, 40 T |
| Bore Diameter Range | 5 mm – 20 mm (round); keyed bores available — see variant options |
| Keyed Bore Options | 10 mm (3×1.4 mm key), 12 mm (4×1.8 mm key), 14 mm (5×2.5 mm key), 15 mm (5×2.3 mm key), 16 mm (5×2.3 mm key), 17 mm (5×2.3 mm / 5×2.5 mm key), 18 mm (6×2.8 mm key), 19 mm (6×2.8 mm key), 20 mm (6×2.8 mm key) |
| Hub Outer Diameter | See variant options |
| Hub Length | See variant options |
| Surface Finish | Natural / lightly oiled (mill finish) |
| Roller Chain Available | 04C, 0.5 m and 5 m lengths (select as variant) |
| Chain Connectors Available | Closed-loop connector; Extension connector (select as variant) |
| Quantity per Order | 1 pcs (default); multi-pack options — see variant options |
The tooth count determines your drive ratio. Divide the driven sprocket teeth by the driver sprocket teeth to get the reduction ratio. For example, a 9 T driver paired with a 27 T driven sprocket gives a 3:1 reduction. Select a smaller tooth count on the motor side for speed reduction and torque multiplication, or match tooth counts for a 1:1 direct drive.
Measure your shaft diameter with a calliper and select the matching bore. For a secure, slip-free connection on a keyed shaft, choose a keyed-bore variant whose key dimensions match your shaft keyway (e.g. a 12 mm shaft with a 4×1.8 mm keyway requires the "12mm(4×1.8mm)" variant). For plain shafts, a round bore with a set screw is typical — drill and tap the hub after delivery if needed.
45# medium-carbon steel has a tensile strength of approximately 600–800 MPa in the normalised condition, making it well suited to light-to-medium duty chain drives such as small conveyors, robotics, e-bikes, and workshop machinery. For heavy shock loads or continuous high-speed industrial duty, consider whether a hardened or alloy-steel sprocket is more appropriate for your specific torque and speed requirements.
The sprockets are supplied with a light mill-finish oil coating that provides short-term corrosion protection during storage and transit. For outdoor or humid environments, apply a chain lubricant or anti-rust spray regularly. If corrosion resistance is a primary requirement, consider stainless-steel sprocket alternatives or apply a suitable surface treatment after purchase.
No. These sprockets are machined specifically for 04C roller chain with a 6.35 mm (0.25 in) pitch. Using them with a different chain pitch — such as 25H, 35, or 06B — will result in poor engagement, accelerated wear, and potential chain derailment. Always match sprocket and chain pitch exactly.
Matching 04C roller chain and chain connectors are available as variant options directly on this listing. Select "Roller Chain" in the Number of Tooth dropdown and then choose your required length (0.5 m or 5 m). For connectors, select "Chain connector (Close)" for a closed-loop link or "Chain connector (Open)" for an extension link. This allows you to source the complete drive system in a single order.
Use the standard chain-length formula: L = 2C/P + (T1+T2)/2 + (T2−T1)²/(4π²C/P), where C is the centre distance, P is the chain pitch (6.35 mm), T1 is the driver tooth count, and T2 is the driven tooth count. Round up to the nearest even number of links and use a chain connector to close the loop. The 0.5 m chain option (approx. 79 links) suits short-centre drives, while the 5 m option covers longer runs or multiple cuts.
