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Finding a sprocket that fits your shaft exactly — without slop, wobble, or guesswork — is one of the most frustrating parts of building a chain drive system. Whether you're a hobbyist assembling a go-kart, a maker building a conveyor, or a technician replacing worn drivetrain components, this #25 roller chain sprocket (04C, 40-tooth) gives you the dimensional precision and bore flexibility to get the job done right the first time.
Each sprocket is machined from carbon steel with a natural or lightly finished surface, featuring a 40-tooth profile engineered for #25 (04C) roller chain with a pitch of 6.35 mm (1/4 inch). Bore options range from 8 mm to 30 mm (~0.31" to 1.18"), with plain round bores and keyed variants (4×1.8 mm, 5×2.3 mm, and 6×2.8 mm, 8×3.3 mm keyways) available to suit standard shaft configurations.
Typical applications include #25 chain go-kart drive systems, small conveyor belt sprocket replacements, DIY robotics and automation chain drives, and light-duty power transmission projects where a compact 1/4-inch pitch sprocket is required. The 40-tooth count delivers a smooth, low-noise engagement ideal for moderate-speed reduction ratios.
Precisely cut 40-tooth geometry matches #25 / 04C roller chain pitch of 6.35 mm (1/4") for accurate, low-vibration engagement across the full tooth wrap.
Available in plain round bores from 8 mm to 30 mm (~0.31" to 1.18"), covering the most common shaft sizes used in DIY and light industrial applications.
Select keyed bore variants (4×1.8 mm, 5×2.3 mm, 6×2.8 mm, or 8×3.3 mm) to lock the sprocket to your shaft and eliminate rotational slip under load.
Machined from carbon steel for reliable strength and wear resistance in typical chain drive environments, including go-karts, conveyors, and automation rigs.
Order as a single piece for a one-off repair, or choose 5-pack or 10-pack quantities for project builds, spare parts inventory, or multi-axis drive systems.
Dimensionally consistent with standard 04C sprocket specifications, making this a reliable drop-in replacement for worn or damaged sprockets in existing #25 chain drives.
| Chain Standard | #25 / 04C |
|---|---|
| Pitch | 6.35 mm (1/4") |
| Number of Teeth | 40T |
| Bore Diameter | 8 mm – 30 mm (See variant options) |
| Keyway Options | Plain bore / 4×1.8 mm / 5×2.3 mm / 6×2.8 mm / 8×3.3 mm (See variant options) |
| Material | Carbon Steel |
| Surface Finish | See variant options |
| Outside Diameter (OD) | See variant options |
| Hub Diameter | See variant options |
| Hub Length | See variant options |
| Weight (per piece) | See variant options |
| Available Quantities | 1 pc / 5 pcs / 10 pcs |
This sprocket is designed for #25 roller chain, also known as 04C chain, with a pitch of 6.35 mm (1/4"). Check the markings on your existing chain or measure the center-to-center distance between two adjacent pins — if it measures 6.35 mm, this sprocket is the correct match.
Measure your shaft diameter with a caliper. Select the bore that matches your shaft exactly — for example, if your shaft is 12 mm, choose the 12 mm bore. If your shaft uses a key for torque transmission, select the corresponding keyway variant (e.g., 12 mm / 5×2.3 mm Keyway). When in doubt, a plain bore can be machined to a custom fit by a local machine shop.
A plain bore is suitable for low-torque applications where the sprocket is secured with a set screw or press fit. For higher-torque drives — such as go-kart axles or motorized conveyors — a keyway bore provides a positive mechanical lock between the sprocket and shaft, preventing rotational slip under load. Check your shaft for an existing keyway slot to determine which option applies.
The sprocket is machined from carbon steel, which provides solid tensile strength for light-to-moderate duty chain drive applications. Exact load ratings depend on the specific bore size and operating conditions. For heavy industrial or continuous high-speed applications, consult the chain manufacturer's load tables and match the sprocket rating to your drive requirements.
Carbon steel has moderate corrosion resistance. For outdoor or humid environments, we recommend applying a light coat of chain lubricant or anti-rust spray to the sprocket surface. If your application requires stainless steel or zinc-plated variants, please contact us to confirm availability.
Yes. This sprocket is manufactured to standard 04C / #25 chain specifications, making it dimensionally compatible with most OEM and aftermarket 40-tooth sprockets of the same pitch. Match the bore size and keyway (if applicable) to your existing sprocket before ordering to ensure a drop-in fit.
Multi-piece packs are ideal for builders running multiple drive axes, teams stocking spare parts for maintenance, or anyone who wants to keep replacement sprockets on hand. The per-unit cost decreases with larger quantities, making packs a practical choice for project builds and workshop inventory.
