Sprockets

Sprockets are the toothed wheels that carry drive power to and from a roller chain or a toothed synchronous belt. Get the pitch, tooth count and bore right and a drive runs for years on routine lubrication; get any one of them wrong and you'll be replacing the mating chain or belt again within months. This collection brings together two related but distinct product families that AIMS stocks under the "Sprockets" range: British Standard (BS/ISO 606) and American Standard (ASA/ANSI B29.1) roller chain sprockets in pilot bore, taper lock, weld-fit and plate wheel styles from Finer Power Transmissions, idler sprockets from Aetna and Finer Power Transmissions, and Gates Poly Chain GT and PowerGrip GT synchronous belt sprockets in steel and stainless. Our Roller Chain: Sizes, Types & Sprockets walks through the key differences if you're comparing options.

If you're not sure which family you need: a roller chain sprocket has square-cut, evenly spaced teeth that seat a chain's rollers, and it must be matched to your chain's standard (BS or ASA) and pitch. A Gates Poly Chain GT or PowerGrip GT sprocket has a curvilinear tooth profile that meshes with a toothed polyurethane or rubber belt, not a chain — the two are not interchangeable. Send us a photo of the worn part if you're unsure which you're holding.

Quick Reference — What's in This Collection

Roller Chain Sprockets — BS & ASA Pitch Reference

Pitch is the centre-to-centre distance between chain pins, and it's the number that must match exactly between chain and sprocket. Our BS and ASA roller chain sprockets are stocked across the pitches below (confirmed from current product and variant data):

Critical rule: BS and ASA pitches are not interchangeable, even where the nominal pitch looks the same (BS 08B and ASA #40 are both roughly 1/2" pitch). Tooth profile, roller diameter and inner width differ between the two standards. Confirm your chain's markings, or send us a photo of the chain side plate, before ordering a replacement sprocket. Need a pitch or tooth count outside this table — give Sam's team a call and we'll check what else can be brought in.

Sprocket Types Stocked at AIMS

By bore & mounting style

• Pilot bore: Ships with a small pilot bore that your workshop machines out and keys to the exact shaft diameter. Maximum flexibility for non-standard shafts. Stocked in both BS and ASA, simplex through triplex.
• Taper lock: Bore is machined to accept a standard taper lock bush, which takes the keyway and grips the shaft via tapered interference — quick to install and remove without disturbing the shaft or adjacent bearings. Stocked in BS simplex, duplex and triplex, in both steel and cast iron, plus a reverse taper lock configuration. See our taper lock bushes range for the matching bush.
• Weld-fit: No finished bore — a tooth ring designed to be welded onto a custom hub or directly to the shaft. Stocked with hardened teeth across 08B and ASA #40/#50/#60/#80, for conveyor head/tail shafts and other high-duty applications.
• Plate wheel: Simple flat-disc sprocket, stocked in both BS (06B–24B) and ASA (#40/#60/#80) pitch families across a wide range of tooth counts — a straightforward option where a plain bore, no-hub sprocket suits the application.

By chain strand

• Simplex (single strand): The most common configuration, paired with single-strand roller chain, and the majority of the taper lock, pilot bore, weld-fit and plate wheel range in this collection.
• Duplex (double strand): Two rows of teeth on one sprocket body for duplex chain, delivering meaningfully more torque capacity than simplex at the same pitch without moving to a larger chain size. Stocked in BS pilot bore and taper lock (steel and cast iron).
• Triplex (triple strand): Three rows of teeth for triplex chain, for heavier drives needing compact high-torque transmission. Stocked in BS pilot bore (steel) and taper lock (steel and cast iron), and ASA pilot bore (steel).

Idler & tensioner sprockets

Idler sprockets ride on the slack side of a chain run to take up tension and correct wrap angle, without driving the load themselves. AIMS stocks a genuinely broad idler range from Aetna — single-pitch and double-pitch idlers in a range of tooth counts and bore sizes, including a heavy-duty double-pitch series, a yellow zinc-plated finish option, an extra-heavy-gauge steel version and a detachable chain idler — alongside purpose-built tensioner idler sprockets from Finer Power Transmissions sized to suit specific SE-series tensioner units (SE-15/8, SE-27, SE-38) and a 20B-1 idler to suit SE-45. Gates also supplies an idler sprocket for use with its synchronous belt drives. If you're matching an idler to an existing tensioner arm, the tensioner's model or SE number is the fastest way to confirm fit.

Synchronous belt (timing) sprockets — Gates Poly Chain GT & PowerGrip GT

These are a different drive family to the roller chain sprockets above — they carry a curvilinear tooth profile designed to mesh with a toothed polyurethane (Poly Chain GT) or rubber (PowerGrip GT) synchronous belt, not with roller chain. Gates uses "sprocket" in the product name because the part looks and functions like one, but it is not chain-compatible. AIMS stocks these in 5MGT, 8M and 14M tooth sections, in both pilot bore and taper lock mounting, with a stainless steel option available in the 8M section for washdown or corrosive environments. If you're specifying a new drive rather than replacing a part, see our timing pulleys range for the fuller Gates synchronous belt drive selection, including belts.

Materials

• Carbon steel: The standard material across the BS and ASA range — pilot bore, taper lock, weld-fit and plate wheel sprockets are predominantly steel. Suits clean, lubricated workshop and conveyor drives.
• Hardened teeth: Our weld-fit range (08B and ASA #40/#50/#60/#80) is supplied with hardened teeth for extended wear life in higher-duty or more abrasive applications than a plain carbon-steel tooth would handle.
• Cast iron: Stocked in BS taper lock duplex and triplex, and BS pilot bore duplex, where a lower-cost, heavier-section wheel suits large-diameter, lower-speed drives.
• Stainless steel: Stocked in BS pilot bore simplex, and in the Gates 8M Poly Chain GT range (both pilot bore and taper lock), for food processing, washdown, marine and corrosive environments.

Selection Criteria

Five questions to answer before ordering:

1. What are you driving — roller chain or synchronous belt? A BS/ASA sprocket needs the matching chain standard and pitch; a Gates Poly Chain GT/PowerGrip GT sprocket needs the matching belt section (5MGT, 8M, 14M) and pitch — the two families are not interchangeable.
2. What's the strand count? Simplex, duplex or triplex for roller chain sprockets — must match your chain exactly.
3. How many teeth? Tooth count sets the drive ratio in combination with the mating sprocket; running too few teeth on a fast-turning sprocket increases chordal action and accelerates wear. Our range spans roughly 8 teeth up to 120+ depending on product.
4. What's your shaft size and bore preference? Pilot bore (you machine it), taper lock (clean install/remove via bush), or weld-fit (custom hub, no finished bore).
5. What's the operating environment? Clean and lubricated suits standard carbon steel; abrasive or high-duty suits hardened-tooth weld-fit; washdown, food or corrosive environments call for stainless.

Installation & Maintenance

Taper lock installation

Install the bush into the sprocket bore (flange side out), align the bolt holes, tap the bush into position, then tighten the cap screws progressively in a star pattern to the bush manufacturer's torque spec. Always use a torque wrench — over-tightening can crack the bush flange, under-tightening lets the sprocket slip under load.

Drive alignment

Both sprockets (or a sprocket and its mating pulley) must be parallel and in the same plane. Check with a straightedge across both faces and a feeler gauge or laser tool to confirm axial offset. Misalignment causes uneven tooth wear and premature failure of both the sprocket and the chain or belt it drives.

Tension

Roller chain should run with a small amount of slack on the non-driving side — too tight overloads bearings and accelerates wear, too loose risks the chain jumping teeth or whipping under shock load. An idler or tensioner sprocket (stocked in this range) sets and maintains that tension over the drive's service life. Synchronous belts run to a specific tension spec from Gates — check the belt datasheet rather than judging by feel.

Lubrication

Roller chain needs lubricant to penetrate the pin-and-bushing joint, not just coat the outer plates — that's the actual wear surface. See our lubrication range for chain-specific lubricants. Poly Chain GT and PowerGrip GT belt drives run dry and need no lubrication — don't oil a synchronous belt drive.

Common Applications

Conveyors

Head and tail shaft drives typically run BS taper lock or pilot bore sprockets, with hardened-tooth weld-fit for continuous-duty installations. Stainless where the line is washdown or food-adjacent.

Mining & Quarry

Heavier BS sizes (16B, 20B, 24B) and ASA hardened-tooth weld-fit sprockets suit screens, feeders and haul conveyors where tooth wear from abrasive material is the limiting factor.

Food & Beverage Processing

Stainless steel BS pilot bore sprockets, or stainless Gates 8M Poly Chain GT sprockets on synchronous belt lines, for washdown hygiene requirements.

Agricultural Machinery

Mix of BS and ASA depending on OEM origin — European-built implements tend BS, North American iron tends ASA. Idler sprockets take up chain tension on variable-load augers and conveyor feeds.

Precision & High-Torque Drives

Gates Poly Chain GT and PowerGrip GT sprockets suit drives that need the positive, no-slip engagement of a synchronous belt without the lubrication and maintenance overhead of roller chain — pumps, compressors, and general power transmission where a dry-running drive is preferred.

Brand Range

• Finer Power Transmissions: Our core roller chain sprocket brand in this collection — BS and ASA pilot bore, taper lock, weld-fit and plate wheel sprockets, plus SE-series tensioner idler sprockets.
• Aetna: Our idler sprocket specialist — single and double-pitch idlers across a wide range of bore sizes and finishes.
• Gates: Poly Chain GT and PowerGrip GT synchronous belt sprockets in 5MGT, 8M and 14M sections, plus a Gates idler sprocket for belt-drive tensioning.

Confirm brand, standard and pitch when ordering a replacement sprocket so the new part matches the rest of your drive.

Companion Collections

• Chain & Sprockets: The full roller chain category hub — BS and ASA roller chain, connecting and offset links, leaf chain and stainless chain, alongside the sprockets on this page.
• Roller Chain: The mating component for our BS/ASA sprockets — order chain and sprockets together when refurbishing a drive.
• Chain Idlers & Accessories: Idler sprockets, tensioners, chain pullers and chain breakers as a dedicated range.
• Timing Pulleys: The broader Gates synchronous belt drive range, including belts, beyond the sprockets stocked here.
• Taper Lock Bushes: Match your taper-lock-bore sprockets to the correct bush size.
• Bearings: Pillow blocks, flange units and inserts for the shafts your sprockets run on.
• Couplings: For connecting motor shafts to driven shafts.
• Key steel and key stock: Square and rectangular key stock for keyway cutting on pilot-bore sprockets.
• Pulleys: If belt drive is the better fit for your application than chain or synchronous belt.
• Lubrication: Chain lubricants for the roller chain side of this range.

Order from AIMS

If you're replacing a worn sprocket, send us the chain or belt markings, the existing sprocket's tooth count, and your shaft diameter (and bore style if known) — we'll match the replacement without guesswork. If you're specifying a new drive from scratch, give Sam's team a call and we'll walk through chain/belt standard, sprocket strand, tooth count, material and bore style with you.

Same-day dispatch on in-stock items from our Milperra warehouse (Sydney NSW). Larger sizes and hardened-tooth or stainless specifications may be indent — we'll confirm freight ETA at order time.

Australian-owned, Sydney based. Call (02) 9773 0122, contact our team, or request a quote with your chain/belt pitch, tooth count and shaft details.

Frequently Asked Questions

What's the difference between a roller chain sprocket and a Gates Poly Chain GT or PowerGrip GT sprocket?

A roller chain sprocket has square-cut teeth that seat the rollers of a BS or ASA roller chain. A Gates Poly Chain GT or PowerGrip GT sprocket has a curvilinear tooth profile designed to mesh with a toothed synchronous belt instead. The two families are not interchangeable — you need the sprocket that matches whichever drive component (chain or belt) you're running.

What's the difference between a pilot bore, taper lock and weld-fit sprocket?

A pilot bore sprocket ships with a small bore that your workshop machines and keys to the exact shaft size. A taper lock sprocket uses a separate tapered bush so the sprocket can be fitted and removed without disturbing the shaft or chain — the most maintenance-friendly option. A weld-fit sprocket has no finished bore at all and is welded directly to the shaft or a custom hub, used where the other two mounting styles aren't practical.

Can I fit a BS sprocket to ASA chain, or the reverse?

No. BS (ISO 606) and ASA (ANSI B29.1) are different standards, and even at similar nominal pitch — BS 08B and ASA #40 are both roughly 1/2" — the tooth profile, roller diameter and inner width differ. Confirm your existing chain's markings before ordering a replacement sprocket, or send us a photo of the chain side plate and we'll identify it.

What's the difference between simplex, duplex and triplex sprockets?

Simplex has a single row of teeth for single-strand chain. Duplex has two rows for duplex (two-strand) chain, and triplex has three rows for triplex chain — both deliver more torque capacity than simplex at the same pitch. Strand count must match exactly between chain and sprocket.

Why replace sprockets and chain together rather than just the worn part?

Chain and sprocket wear happen together. A new chain run on worn sprocket teeth wears out again quickly because the worn tooth pockets concentrate load and stretch the new chain; new sprockets on a stretched chain see accelerated tooth wear in return. Replacing both together is what gets you the full service life from either.

Do you stock stainless steel sprockets for food or washdown environments?

Yes — BS pilot bore simplex sprockets in stainless steel, and Gates 8M Poly Chain GT sprockets (pilot bore and taper lock) in stainless steel for synchronous belt drives.

What is an idler sprocket used for?

An idler sprocket rides on the slack side of a chain run to take up tension and maintain correct wrap angle — it doesn't drive the load itself. We stock a broad Aetna idler range plus purpose-built Finer Power Transmissions tensioner idlers sized to common SE-series tensioner units, and a Gates idler for synchronous belt drives.

What pitch sizes do you stock for BS and ASA sprockets?

BS/ISO 606 from 05B through to 24B, and ASA/ANSI from #40 through to #80, across the pilot bore, taper lock, weld-fit and plate wheel range — with hardened-tooth weld-fit specifically available in 08B and ASA #40/#50/#60/#80. If you need a size outside that range, call us and we'll check what can be brought in.

What tooth counts are available?

Tooth counts across this range run from as few as 8–9 teeth on some idler and plate wheel sprockets up to 120+ on larger plate wheel and pilot bore sprockets, depending on the specific product. Fewer teeth on a fast-turning sprocket increases chordal action and wear, so more teeth generally means smoother, longer-lived running where space allows.