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When a worn or undersized sprocket causes chain skip, premature wear, or misalignment on your drive system, finding an exact-fit replacement becomes urgent. These 04C roller chain sprockets are designed for engineers, machine builders, and hands-on makers who need a dimensionally accurate, ready-to-bore sprocket that drops straight into their drivetrain without guesswork.
Each sprocket is machined from carbon steel and supplied as a pilot bore (unfinished bore) component, allowing you to finish-bore and key the hub to your exact shaft size. The bore range spans 8 mm to 20 mm (approximately 0.31" to 0.79"), with tooth counts of 26T, 27T, 28T, 29T, and 30T. Many variants are also available pre-finished with keyway slots (e.g., 5×2.3 mm or 6×2.8 mm keyways) for direct shaft mounting. Chain pitch conforms to the 04C standard (6.35 mm / 0.25").
Typical applications include small conveyor drives, robotics and automation rigs, go-kart and mini-bike transmissions, agricultural equipment, and DIY power-transmission projects where a compact 04C chain drive is specified. The multi-piece quantity options (1 pc, 3 pcs, 5 pcs) make it straightforward to stock spares or outfit a full drive system in a single order.
| Chain Standard | 04C (metric roller chain) |
|---|---|
| Chain Pitch | 6.35 mm (0.25") |
| Tooth Count Options | 26T, 27T, 28T, 29T, 30T |
| Bore Diameter Range | 8 mm – 20 mm (0.31" – 0.79") |
| Bore Type | Pilot bore (plain) or keyway-slotted (see variant options) |
| Keyway Options | 3×1.4 mm, 4×1.8 mm, 5×2.3 mm, 6×2.8 mm (see variant options) |
| Material | Carbon steel |
| Surface Finish | See variant options |
| Hub Style | Pilot bore (unfinished / pre-finished keyway) |
| Quantity per Order | 1 pc / 3 pcs / 5 pcs (see variant options) |
| Weight | 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 30T driven sprocket paired with a 15T driver gives a 2:1 reduction. Higher tooth counts on the driven side slow the output shaft and increase torque; lower counts increase speed. Match your tooth count to the gear ratio your application requires.
A pilot bore sprocket ships with a small, undersized center hole (the "pilot"). A machinist bores this out to your exact shaft diameter and cuts a keyway if needed. If you select a variant labeled with a specific bore size and keyway dimension (e.g., "Hole 14mm/5×2.3"), that bore is already finished to that size — no further machining is required for that shaft diameter.
Select the bore diameter that matches your shaft diameter exactly. If your shaft is 12 mm, choose a "Hole 12mm" variant. If you need a keyway, select the variant that specifies both the bore diameter and keyway dimensions (e.g., "Hole 12mm/4×1.8" means a 12 mm bore with a 4 mm wide × 1.8 mm deep keyway). If your shaft size is not listed, choose a plain pilot bore variant and have it finish-bored by a machinist.
These sprockets are designed exclusively for 04C roller chain, which has a 6.35 mm (0.25") pitch. They are not interchangeable with 25H, 35, 40, or other chain standards. Always verify your chain's pitch marking before ordering — using a mismatched sprocket will cause rapid wear and potential chain failure.
The sprockets are machined from carbon steel, which provides solid tensile strength suitable for the load ratings of 04C chain. They are appropriate for light-to-medium duty continuous applications such as conveyors, robotics, and small engine drives. For heavy shock-load or high-speed applications, confirm that the 04C chain's rated working load is not exceeded.
Carbon steel sprockets will oxidize if exposed to moisture without protection. For indoor or dry environments, standard lubrication with chain oil is sufficient. For humid or outdoor environments, apply a rust-inhibiting coating or grease after installation. Some variants (e.g., "blackened" finish) have a basic oxide treatment that provides light corrosion resistance. Check the specific variant description for finish details.
Yes. 04C chain and matching sprockets are commonly used in small go-kart and mini-bike applications where compact, lightweight drive systems are needed. Ensure your engine output shaft and axle shaft diameters fall within the 8–20 mm bore range offered, and select the appropriate keyway variant to secure the sprocket against rotational slip.
Plain hole variants (e.g., "Hole 10mm") have a smooth circular bore — the sprocket is held on the shaft by a set screw, interference fit, or further machining. Keyway variants (e.g., "Hole 10mm/4×1.8") include a milled slot that accepts a standard key, providing a positive, non-slip connection between the sprocket and shaft. Keyway mounting is recommended for any application with significant torque or reversing loads.
