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When your chain drive slips, wears unevenly, or fails to transmit torque cleanly, the culprit is often a sprocket that wasn't machined to spec. Makers, machine builders, and mechanical engineers who need a dependable 04C-pitch sprocket — without sourcing headaches — will find this 45# carbon steel wheel a direct, no-compromise solution.
Each 04C roller chain sprocket is machined from 45# medium-carbon steel, delivering a tensile strength typically in the 600–800 MPa range before surface treatment. The pitch is 6.35 mm (1/4 in), conforming to the ISO 04C / ANSI #25 chain standard. Tooth counts span 21 to 40 teeth, and bore diameters range from 6 mm (0.24 in) to 30 mm (1.18 in) depending on the selected variant. Three bore configurations are available: through-hole (plain bore), keyway hole (with standard metric keyway), and D-hole (flat-sided shaft fit).
Typical use cases include small conveyor systems requiring a compact 1/4-inch pitch chain drive, robotics and automation rigs where a low-backlash 04C sprocket reduces positioning error, and DIY power-transmission builds such as go-karts, mini-bikes, and custom gearboxes where an ANSI #25 chain sprocket with a machined keyway simplifies shaft coupling.
Machined from 45# medium-carbon steel for a balance of machinability and mechanical strength, suitable for moderate-load chain drive applications.
6.35 mm pitch conforms to the international 04C standard, ensuring direct interchangeability with any compliant #25 roller chain on the market.
Choose through-hole for press-fit or set-screw mounting, keyway hole for positive torque transmission with a standard metric key, or D-hole for flat-shaft motor output shafts.
Sixteen tooth-count options from 21 T to 40 T let you dial in the exact speed ratio your drive system requires without custom fabrication.
Bore options from 6 mm to 30 mm cover the majority of small-to-medium shaft diameters used in hobby, light industrial, and automation builds.
Teeth are cut to the standard 04C involute profile, promoting even chain engagement, reduced noise, and extended chain life compared to non-standard profiles.
| Chain Standard | ISO 04C / ANSI #25 |
|---|---|
| Pitch | 6.35 mm (1/4 in) |
| Material | 45# Carbon Steel |
| Tooth Count Range | 21 T – 40 T (16 options) |
| Bore Type Options | Through-Hole, Keyway Hole, D-Hole |
| Bore Diameter Range | 6 mm – 30 mm (varies by tooth count) |
| Keyway Dimensions | See variant options |
| Hub Diameter | See variant options |
| Overall Width | See variant options |
| Surface Treatment | See variant options |
| Tensile Strength (typical) | 600–800 MPa (45# steel, untreated) |
| 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 40 T driven sprocket paired with a 20 T driver gives a 2:1 reduction. Choose a tooth count that achieves your target output speed while keeping chain tension within the chain's rated load.
A through-hole (plain bore) relies on a set screw or interference fit to secure the sprocket to the shaft. A keyway hole includes a machined slot that accepts a standard metric key, providing positive torque transmission without relying solely on friction — recommended for higher-torque or reversing loads. A D-hole has one flat side matching a D-shaped motor output shaft, common on small gearmotors and hobby motors.
Yes — this sprocket is machined to the ISO 04C / ANSI #25 standard with a 6.35 mm pitch. Any compliant #25 roller chain with a 3.30 mm roller diameter will mesh correctly. Confirm your chain's pitch marking (usually stamped on the link plate) before ordering.
45# carbon steel has a typical tensile strength of 600–800 MPa in the normalized or quenched-and-tempered condition, making it suitable for light-to-moderate power transmission loads. For heavy shock loads or continuous high-speed operation, consider whether additional surface hardening (e.g., induction hardening) is required for your specific duty cycle. Contact us to confirm suitability for demanding applications.
Use a digital caliper to measure the shaft diameter at the mounting location. Select the bore size that matches your shaft diameter exactly for a through-hole or D-hole fit. For keyway variants, also note the keyway width and depth (shown in the variant name, e.g., "14mm(5×2.3mm)" means 14 mm bore with a 5 mm wide × 2.3 mm deep keyway). If your shaft is between listed sizes, a machine shop can finish-bore a larger plain-bore sprocket to your exact dimension.
Yes. Like all steel roller chain sprockets, regular lubrication of the chain-sprocket interface extends service life significantly. Apply a light chain oil or grease to the chain at regular intervals based on your operating speed and environment. In dusty or wet conditions, more frequent lubrication and inspection are recommended.
This 04C / #25 pitch sprocket is well-suited for small go-kart and mini-bike drivetrains that use #25 chain. Verify that your engine output shaft diameter matches the available bore sizes, and select the keyway variant if your shaft has a keyway for secure torque coupling. Always confirm the sprocket's rated load capacity against your engine's peak torque output before finalizing your build.
