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When your chain drive slips, wears unevenly, or simply won't mesh cleanly, the culprit is almost always a mismatched or worn sprocket. Whether you're a robotics hobbyist, a small-machine builder, or a DIY drivetrain enthusiast, these 04C B-type roller chain sprockets give you the exact tooth count and bore size you need to build a reliable, low-backlash chain drive from scratch.
Each sprocket is machined from 45# medium-carbon steel and finished with a natural steel surface. The B-type hub profile features a rough bore ranging from 5 mm (0.20 in) to 12 mm (0.47 in) depending on the variant selected, with an outer diameter that scales proportionally from approximately 20 mm (0.79 in) on the 8T up to roughly 165 mm (6.50 in) on the 80T. All sprockets are cut to the 04C / #25 standard with a 6.35 mm (1/4 in) pitch, matching standard 04C roller chain.
Typical use cases include compact conveyor systems requiring a 04C sprocket for light-load transport, RC and hobby robotics builds needing a small-pitch chain sprocket with a 6 mm or 8 mm bore, and DIY automation projects where a 45-steel B-type sprocket provides the strength-to-weight ratio needed for intermittent-duty cycling. The included roller chain and chain link variants let you complete the entire drivetrain in one order.
From compact 8-tooth pinions to large 80-tooth driven sprockets, the full range lets you dial in your exact gear ratio without custom machining.
Machined from 45# steel for a balance of machinability and tensile strength, suitable for light-to-medium duty intermittent drives and DIY automation.
Tooth geometry conforms to the 04C (#25) chain standard at 6.35 mm pitch, ensuring consistent mesh with any compliant 04C roller chain.
Choose from 5 mm, 6 mm, 8 mm, 10 mm, or 12 mm rough bores to match your shaft diameter, or bore-out to a custom size on a lathe.
Order a single sprocket for a prototype, a pair for a matched drive, or a 5-piece pack for spares — all at consistent per-unit pricing.
Roller chain (0.5 m–10 m lengths), chain links, and half links are available as variants so you can source the full 04C drive assembly together.
| Chain Standard | 04C / #25 |
|---|---|
| Pitch | 6.35 mm (1/4") |
| Sprocket Type | B-Type (hub both sides) |
| Tooth Count Range | 8T – 80T (sprockets); Roller Chain & Chain Link variants also available |
| Material | 45# Medium-Carbon Steel |
| Surface Finish | Natural steel (uncoated) |
| Rough Bore Diameter | 5 mm / 6 mm / 8 mm / 10 mm / 12 mm (see variant options) |
| Outer Diameter | See variant options |
| Hub Diameter | See variant options |
| Hub Length | See variant options |
| Keyway | Contact us to confirm |
| Available Quantities | 1 pcs / 2 pcs / 5 pcs |
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 10T driver paired with a 30T driven sprocket gives a 3:1 reduction. Start with your required output speed and torque, then work backwards to select the tooth counts. Smaller sprockets (8T–15T) are typically used as drive pinions; larger sprockets (30T–80T) are used on the driven shaft.
Order the rough bore that is equal to or slightly smaller than your shaft diameter. The rough bore is an unfinished hole that you can bore, ream, or broach to your exact shaft size and add a keyway if needed. If your shaft is 6 mm, order the 6 mm rough bore. If your shaft is 7 mm, order the 8 mm rough bore and machine it down.
Yes. The 04C standard is the metric equivalent of the ANSI #25 chain standard, both sharing a 6.35 mm (1/4") pitch. These sprockets are designed to mesh with any 04C or #25 compliant roller chain. Always verify the chain's inner width and roller diameter match the sprocket tooth profile before assembly.
45# medium-carbon steel has a typical tensile strength of approximately 600–800 MPa after normalizing. It is well-suited for light-to-medium duty intermittent drives such as robotics, small conveyors, and hobby machinery. For continuous heavy-duty industrial applications, consider heat-treated or alloy-steel sprockets. If you are unsure whether this material meets your load requirements, contact us with your torque and speed specifications.
The sprockets are supplied with a natural steel finish and are not coated or plated. Like all uncoated carbon steel parts, they will oxidize if exposed to moisture. For outdoor or humid environments, apply a light machine oil or anti-rust spray after installation and re-apply periodically. For corrosive environments, consider stainless steel alternatives.
Yes. Select "Roller Chain" under Number of Teeth and then choose your required length (0.5 m, 1.5 m, 5 m, or 10 m) from the Rough Bore Diameter dropdown. For connecting links, select "Chain Link" or "Half Link" and choose the 1/4" size. This lets you complete your entire 04C drivetrain in a single order.
A chain link (also called a master link or connecting link) is a full-pitch link used to join two ends of a roller chain. A half link is a half-pitch link used to fine-tune chain length by one half-pitch increment when a full link would make the chain too long. Use a half link only when necessary, as it is slightly weaker than a standard link and should be avoided in high-load applications.
