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When a worn or mismatched sprocket causes chain skipping, premature wear, or unexpected downtime on your project, finding a dimensionally accurate replacement becomes critical. Makers, hobbyists, and mechanical engineers working with compact #25 / 04C chain drive systems need a sprocket that holds tight tolerances without requiring custom machining. This 200X 25H 04C roller chain sprocket is engineered for that exact use case.
This sprocket is machined from C45 medium-carbon steel and finished with a black oxide coating for corrosion resistance. It features 12 teeth, a 1/4" (6.35 mm) chain pitch conforming to the 04C / 25H standard, and a 10 mm bore diameter. The hub is designed to accept a standard set-screw for shaft retention. Overall sprocket outer diameter is typically 25–30 mm depending on tooth geometry, with a hub length of approximately 15–25 mm.
Typical applications include small conveyor systems, go-kart or mini-bike secondary drives, robotics and automation platforms, and DIY power transmission builds requiring a compact 1/4" pitch chain sprocket with a 10mm bore. This sprocket is also a direct fit for 25H chain used in motorized bicycle and light industrial equipment projects.
| Chain Standard | 04C / 25H / #25 |
|---|---|
| Chain Pitch | 1/4" (6.35 mm) |
| Number of Teeth | 12 |
| Bore Diameter | 10 mm |
| Material | C45 Medium-Carbon Steel |
| Surface Finish | Black Oxide |
| Outer Diameter | See variant options |
| Hub Length | See variant options |
| Shaft Retention | Set-Screw |
| Keyway | Contact us to confirm |
| Weight | See variant options |
| Applicable Chain Roller Width | 3/16" (4.76 mm) |
This sprocket is designed for #25 / 04C / 25H roller chain with a 1/4" (6.35 mm) pitch and a 3/16" (4.76 mm) roller width. It will not fit #35 or other pitch chains. Always verify your chain's pitch and roller width before ordering.
Yes — the 10 mm bore is sized for standard metric shafts. The set-screw hub allows you to lock the sprocket onto the shaft without a keyway. If your shaft is imperial (e.g., 3/8"), you will need a bore adapter or a different variant.
C45 medium-carbon steel has a tensile strength of approximately 600–800 MPa in its normalized state, making it well-suited for light-to-medium duty chain drive applications. For high-shock or continuous heavy-load environments, consider a hardened or alloy steel sprocket.
Black oxide provides a mild base layer of corrosion resistance and is suitable for indoor or low-humidity environments. For outdoor or wet applications, we recommend applying a light machine oil or grease to the sprocket surface periodically to extend service life.
Yes — 25H chain is dimensionally equivalent to 04C chain (1/4" pitch). This 12-tooth sprocket is a common secondary drive sprocket for motorized bicycle builds. Confirm your existing sprocket's tooth count and bore size match before purchasing.
The number of teeth on your sprocket determines your drive ratio. A 12-tooth driver paired with a larger driven sprocket produces speed reduction and torque multiplication. Use the formula: Driven RPM = Driver RPM × (Driver Teeth ÷ Driven Teeth). Choose your tooth count based on the speed and torque requirements of your application.
This sprocket is sized for #25 / 04C chain, which is lighter than the #35 or #40 chain typically used on full-size go-karts. It is well-suited for mini-bikes, pocket bikes, and small motorized platforms that use 1/4" pitch chain. Verify your chain standard and shaft diameter before ordering.
