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When a worn or mismatched sprocket causes chain skip, premature wear, or drivetrain noise, finding an exact-fit replacement becomes critical. Engineers, hobbyists, and machine builders working with 04C roller chain systems need a sprocket that delivers dimensional accuracy and consistent engagement — this 04C pilot bore sprocket is designed for exactly that application.
This sprocket is machined from carbon steel and features a pilot bore design, allowing the bore to be finish-machined to your exact shaft diameter. Available in tooth counts from 9T to 16T and bore diameters ranging from 5 mm (0.197 in) to 15 mm (0.591 in), with select variants offering keyway-ready stepped bores (e.g., 8/3×1.4 mm, 10/4×1.8 mm, 12/5×2.3 mm). Sold in quantities of 1, 3, or 5 pieces per order.
Typical use cases include light-duty conveyor drives requiring a compact 04C chain drive sprocket, small engine timing and power transmission assemblies needing a replacement roller chain sprocket 9 tooth through 16 tooth, and custom DIY automation rigs where a pilot bore sprocket for 04C chain allows on-site bore finishing to match non-standard shaft sizes.
| Chain Standard | ISO 04C / DIN 8187 |
|---|---|
| Chain Pitch | 6.35 mm (0.25 in) |
| Number of Teeth | 9T, 10T, 11T, 12T, 13T, 14T, 15T, 16T |
| Bore Diameter | 5 mm, 6 mm, 6.35 mm, 7 mm, 8 mm, 10 mm, 12 mm, 14 mm, 15 mm; stepped keyway bores available — See variant options |
| Material | Carbon Steel |
| Bore Type | Pilot Bore (finish-machine to shaft size) |
| Hub Style | See variant options |
| Weight | See variant options |
| Quantity per Order | 1 pcs / 3 pcs / 5 pcs |
| Surface Finish | See variant options |
| Application | Light-duty roller chain power transmission, conveyor drives, DIY automation |
| Compatibility Note | Designed for 04C single-strand roller chain only |
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 9T driver paired with an 18T driven sprocket gives a 2:1 reduction. Lower tooth counts (9T–11T) suit higher-speed, lower-torque applications; higher counts (14T–16T) are better for slower, higher-torque drives. Always verify chain wrap angle — a minimum of 120° on the small sprocket is recommended for reliable engagement.
A pilot bore sprocket is supplied with a bore diameter smaller than the intended shaft size. You (or a machine shop) finish-bore it to your exact shaft diameter on a lathe. This approach gives you a precise interference or clearance fit and allows the same sprocket blank to fit a range of shaft sizes. If your shaft matches one of the listed bore options exactly, confirm whether the bore is already finish-machined or still requires boring — check the variant description carefully.
Stepped bore variants have a main bore diameter followed by a keyway slot dimension. For example, "8/3×1.4mm" means the bore is 8 mm in diameter with a 3 mm wide × 1.4 mm deep keyway slot cut into it. This allows a keyed shaft to transmit torque without slipping. Match the keyway dimensions to your shaft's key stock size. If your shaft has no keyway, select a standard round bore variant instead.
No. This sprocket is designed specifically for 04C roller chain (6.35 mm pitch, ISO 04C / DIN 8187). It is not interchangeable with 04B chain (which has a different pitch and roller diameter) or ANSI 25 chain (also 6.35 mm pitch but with different roller and plate dimensions). Always verify the chain standard before ordering to ensure correct tooth profile engagement.
Order 1 piece for a single-machine repair or prototype build. Choose 3 pieces if you're building a multi-axis system or want a spare on hand. The 5-piece option offers the best per-unit value and is suited for small production runs or maintenance stock. All quantity variants ship as individual sprockets of the same tooth count and bore size.
Measure your chain's pitch (the distance between pin centers on adjacent links). If it measures 6.35 mm (¼ inch), your chain is 04C compatible. Also check the roller diameter and inner width of your chain against the sprocket tooth profile. If you have the chain manufacturer's part number, cross-reference it against the ISO 04C standard to confirm compatibility before ordering.
Service life depends on load, speed, lubrication, and alignment. Carbon steel sprockets in properly lubricated, well-aligned 04C chain drives typically outlast the chain by a significant margin under light-to-moderate loads. Replace the sprocket whenever tooth wear causes the chain to ride high on the teeth ("hooked" profile), or when chain elongation exceeds 2% of nominal pitch length. Always replace chain and sprocket together when either shows significant wear.
