Your payment information is processed securely. We do not store credit card details nor have access to your credit card information.
When a roller chain drive runs slack, vibration increases, efficiency drops, and premature wear follows. Engineers, fabricators, and DIY machine builders who need a dependable tensioning solution turn to a dedicated idler sprocket — one that holds chain tension without adding load to the drive shaft. This 1/2" pitch steel idler sprocket with ball bearing is engineered specifically for 08B roller chain tensioner applications, giving you a stable, low-friction contact point that keeps your chain taut under varying loads.
Each sprocket is machined from carbon steel and finished to resist surface wear. Tooth counts range from 13 to 19 teeth, with bore sizes spanning 10 mm (0.39 in) to 20 mm (0.79 in). Single-bearing variants suit lighter-duty or space-constrained installations; double-bearing variants provide added radial support for higher-load or higher-speed applications. Chain pitch is 1/2" (12.7 mm), conforming to the 08B ISO standard.
Typical use cases include conveyor tensioner assemblies, agricultural machinery chain drives, go-kart and mini-bike drivetrain tensioners, and custom power-transmission rigs where an 08B roller chain idler sprocket with adjustable bore is required. The available bore range makes this sprocket compatible with a wide variety of shaft diameters without custom machining.
| Chain Standard | 08B ISO (BS) |
|---|---|
| Chain Pitch | 1/2" (12.7 mm) |
| Roller Diameter (chain) | 5/16" (7.94 mm) |
| Number of Teeth | 13 / 15 / 17 / 19 (see variant options) |
| Bearing Type | Single Ball Bearing / Double Ball Bearings (see variant options) |
| Bore Size | 10 mm / 12 mm / 15 mm / 17 mm / 20 mm (see variant options) |
| Material | Carbon Steel |
| Outer Diameter | See variant options |
| Hub Width | See variant options |
| Finish | See variant options |
| Quantity per Order | 1 pc |
| Weight | See variant options |
This sprocket is designed for 08B ISO (British Standard) roller chain with a 1/2" (12.7 mm) pitch and a 5/16" (7.94 mm) roller diameter. It is not interchangeable with ANSI #40 chain, which shares the same pitch but has a different roller diameter. Always confirm your chain's ISO or ANSI designation before ordering.
Single-bearing idler sprockets are suited for lighter loads, lower speeds, and space-constrained installations where minimizing weight matters. Double-bearing variants provide greater radial support, making them the better choice for higher chain tension, higher RPM, or applications where the idler shaft experiences significant side loading. If in doubt, the double-bearing option offers a wider safety margin.
Measure your idler shaft diameter with a caliper and select the matching bore: 10 mm, 12 mm, 15 mm, 17 mm, or 20 mm. The bore should be a close sliding fit on the shaft — not loose. If your shaft diameter falls between available sizes, choose the next smaller bore and have it bored out by a machine shop, or use a shaft sleeve to step up to the next available size.
For idler/tensioner applications, tooth count affects the wrap angle and the smoothness of chain engagement. A 13-tooth sprocket is compact and suits tight-space tensioners; 15–17 teeth offer a balance of size and smooth engagement; 19 teeth provide the largest contact arc and the gentlest chain articulation angle. Match the tooth count to the available space in your tensioner bracket and the minimum wrap angle your drive requires.
The sprocket is machined from carbon steel, which provides good mechanical strength but has limited inherent corrosion resistance. For outdoor, humid, or washdown environments, apply a chain lubricant or anti-rust coating regularly. If your application demands higher corrosion resistance, consider stainless steel alternatives or apply a protective surface treatment after installation.
This sprocket is designed for idler/tensioner use — it spins freely on a fixed shaft via its ball bearing. It is not intended to be keyed or locked to a rotating drive shaft for power transmission. Using it as a drive sprocket would bypass the bearing and could damage the bore or bearing race. For driven applications, use a standard 08B sprocket with a keyway and set-screw hub.
The integrated ball bearing is typically pre-greased and sealed for maintenance-free operation under normal conditions. For high-temperature or high-load environments, inspect the bearing periodically and re-grease if the bearing type allows access. Additionally, keep the chain itself lubricated with a suitable roller chain oil to reduce wear on the sprocket teeth and extend service intervals.
