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When a worn or mismatched sprocket causes chain skip, vibration, or premature wear on your drive system, the fix starts with a correctly bored, correctly toothed wheel. Makers, machine builders, and mechanical hobbyists who need a reliable 04C-pitch sprocket with a ready-to-bore or finished pilot bore will find this range covers the most common shaft diameters without custom machining.
These sprockets are machined from carbon steel and are designed for use with 04C (also known as 25H or 1/4" pitch) roller chain. The pilot bore hub accepts finished bore diameters from 6mm to 20mm (~0.24 in to 0.79 in), with tooth counts spanning 21T through 25T. Plain round bores, keyway bores (3×1.4mm, 4×1.8mm, 5×2.3mm, 6×2.8mm, 8×3.3mm), and D-bore / oval-bore configurations are available across the range.
Typical use cases include small conveyor drives, go-kart and mini-bike final drives, 3D printer and CNC axis drives using 04C chain, and light-duty agricultural or garden equipment reduction stages — all applications where a compact, low-pitch chain drive is preferred over belt or gear transmission.
| Chain Standard | 04C / 25H / 1/4" pitch roller chain |
|---|---|
| Tooth Count Options | 21T, 22T, 23T, 24T, 25T |
| Bore Diameter Range | 6mm – 20mm (≈0.24 in – 0.79 in) |
| Bore Type | Plain round bore; keyway bore (3×1.4mm / 4×1.8mm / 5×2.3mm / 6×2.8mm / 8×3.3mm); oval/D-bore (see variant options) |
| Material | Carbon steel |
| Chain Pitch | 6.35mm (1/4 in) |
| Roller Diameter | 3.30mm (typical for 04C) |
| Hub Style | Pilot bore (finished to selected diameter) |
| Pack Quantity | 1 pcs / 3 pcs / 5 pcs (see variant options) |
| Surface Finish | See variant options |
| Weight (per piece) | See variant options |
The tooth count determines your drive ratio. Divide the driven sprocket teeth by the driving sprocket teeth to get the ratio. A 21T driving sprocket paired with a 42T driven sprocket gives a 2:1 reduction. Use fewer teeth on the driving side for more speed, more teeth for more torque. For most light-duty conveyor and go-kart applications, 21T–25T on the drive side is a common starting point.
Select a plain bore if your shaft uses a set screw or interference fit. Choose a keyway bore if your shaft has a machined keyway slot — match the keyway dimensions (e.g., 4×1.8mm) to your shaft specification. D-bore and oval-bore options (e.g., Hole 8×7mm) are designed for non-round shaft ends such as motor output shafts with a flat. Always measure your shaft before ordering.
Yes. The 04C standard is dimensionally equivalent to the 25H (heavy) and standard 1/4" pitch roller chain used in North America. The 6.35mm pitch and 3.30mm roller diameter are shared across these designations, so 04C sprockets engage correctly with 25H chain and vice versa.
04C chain drives are rated for light-duty applications. The carbon steel construction provides adequate strength for conveyor systems, small reduction drives, and hobby machinery. For exact load ratings, refer to the 04C chain manufacturer's published breaking load and working load limits, and ensure your sprocket tooth count and chain speed stay within those parameters. These sprockets are not intended for heavy industrial or high-shock-load applications.
Use a digital caliper to measure the shaft outer diameter at the point where the sprocket will sit. Round to the nearest 0.5mm and select the matching bore option. For keyway shafts, also measure the keyway width and depth (e.g., a 4mm wide × 1.8mm deep keyway = 4×1.8mm). If your shaft falls between listed sizes, contact us to confirm the closest available bore before ordering.
Carbon steel sprockets will oxidize if exposed to moisture without protection. For outdoor or wet-environment use, apply a chain lubricant or anti-corrosion coating regularly, or consider stainless steel alternatives for long-term corrosion resistance. Routine lubrication of both the chain and sprocket teeth will significantly extend service life in any environment.
Yes. This listing covers sprockets only. You will need a separate 04C / 25H roller chain cut to the correct length for your drive center distance. Use the standard chain length formula: L = (2C/P) + (T1+T2)/2 + (T2−T1)²/(4π²C/P), where C is center distance, P is pitch, and T1/T2 are tooth counts. A chain tool or master link will also be needed for assembly.
