V-Pulleys

V-pulleys (also called V-belt sheaves) are grooved wheels that transmit rotational power through a matched V-belt. The V-shaped groove forces the belt deeper under load — multiplying grip without the high installation tension a flat belt drive demands. Done right, a V-belt drive is one of the most forgiving, low-maintenance power transmission methods in industrial use; done wrong, premature belt failure is almost always traced back to the pulley, not the belt. We've put together a Pulley Types Guide: V-Belt Sheaves, Taper Lock & Selection if you'd like more detail before you buy.

AIMS Industrial holds V-pulleys in stock across the SPZ/Z, SPA/A, SPB/B and SPC/C belt sections, in pilot bore, taper-lock and Mi-Lock (Bi-Loc) bore configurations, in both cast iron and aluminium. Larger D and E section pulleys, and keyed solid bore configurations, can be sourced to special order — call our team for lead times and pricing.

Quick Reference — V-Pulley Selection

Note: minimum recommended pitch diameters are typical industry guidance and vary slightly with belt cord construction — check the belt manufacturer's current selection tables (e.g. Gates, Optibelt, ContiTech) before finalising a non-standard or high-speed drive.

Bore Types — Pilot, Taper-Lock & Mi-Lock

Bore selection has more impact on long-term maintenance cost than most buyers realise. The industry generally offers four configurations:

Pilot bore

Supplied with an undersized bore that gets machined to your shaft diameter in-workshop, with a keyway broached to match. Most precise shaft fit but commits the pulley to one shaft size forever. Best when the drive is a long-term fixture and the shaft size is non-standard. AIMS holds pilot bore pulleys in both cast iron and aluminium.

Keyed solid bore

Finish-bored to a standard metric or imperial shaft size with a keyway already broached — a drop-on fit with the lowest cost per pulley, at the expense of carrying separate stock for every shaft size. Common across the industry for standard shaft diameters (19, 24, 25, 28, 32, 38, 42mm etc.); available at AIMS to special order — ask our team for current lead times.

Taper-lock bore

The pulley accepts a Fenner-pattern taper-lock bush. The bush is sized to the shaft — three or four grub screws draw it into the taper and clamp it onto the shaft. One pulley accepts dozens of bush sizes; replacing the pulley doesn't need a shaft pull, and removal is just backing the grub screws off and using the jacking thread to break the taper. Higher upfront cost than keyed solid bore, but the labour saving on every install and replacement makes taper-lock the default for any multi-belt drive or any drive where the pulley will be removed more than once. This is AIMS' largest in-stock bore category, covering SPZ/Z through SPC/C sections.

Mi-Lock (Bi-Loc) bore

An alternative proprietary bore-locking system, stocked by AIMS in place of — not interchangeable with — the Fenner-pattern taper-lock system above. Like taper-lock, the pulley bore accepts a separate, numbered bush (No.1, No.2 etc.) rather than being finish-bored, so one pulley can suit a range of shaft sizes. The bush numbering and taper profile are specific to the Mi-Lock/Bi-Loc system, so check which system an existing pulley uses before ordering a replacement bush — the two are not cross-compatible.

Materials — Cast Iron, Aluminium & Steel

Pulley material drives service life, maximum safe RPM and cost.

Cast iron

The workhorse choice — typically grey cast iron to AS 1830 grade. Damps belt vibration well, machines cleanly for keyways, and holds groove geometry under sustained load. Heavy, and limited in maximum safe RPM by hoop stress. As a general guide, the default for any drive above roughly 5kW. This is AIMS' primary in-stock material, across taper-lock, pilot bore and Mi-Lock configurations.

Aluminium

Lighter, cheaper, easier to machine — but lower strength and softer groove walls that wear faster under sustained load. Suits fractional-kW drives, light-duty workshop equipment, and applications where rotational mass matters (vertical-shaft mountings, frequent start-stop). Generally not recommended for sustained loads above roughly 3kW or abrasive-dust environments. AIMS stocks aluminium pilot bore pulleys in A and B sections.

Steel

Used for heavy-duty applications where cast iron's brittleness is a risk (impact loads, low-temperature environments, very high RPM). Typically fabricated rather than cast, costs significantly more, and over-specified for most workshop drives — specify only when the manufacturer's drive design calls for it. Available at AIMS to special order.

Belt Section Compatibility

V-pulley grooves must match the belt section exactly. A mismatched belt will sit too high or too low in the groove, contact the groove walls incorrectly, and fail within a few hundred hours. Approximate power-per-belt figures below are general industry guidance — always check the belt manufacturer's current rating tables for a specific drive design.

Narrow sections (SPZ, SPA, SPB, SPC) are the modern standard — deeper groove geometry transmits more power per belt than the classical equivalents and runs cooler. Classical sections (Z, A, B, C, D, E) remain in service on older equipment. The two are not interchangeable — a B-section belt will not run correctly in an SPB groove and vice versa. If you're not sure which section an existing belt is, our V-belt sizing & identification guide covers how to read the markings.

Sizing & Pitch Diameter

Two diameters get quoted on V-pulleys, and confusing them is a common source of speed-ratio errors:

• Pitch Diameter (PD) — the diameter at which the belt's neutral axis sits in the groove. This is the number used in speed ratio, belt length and drive design calculations.
• Outside Diameter (OD) — the physical outer edge of the pulley. Used for clearance and guard sizing only, never for drive calculations.

The speed ratio formula uses pitch diameters: V₂ = V₁ × (D₁ ÷ D₂) — where V₁ is driver RPM, D₁ is driver PD, D₂ is driven PD, V₂ is driven RPM.

Worked example: A 1,440 RPM motor with a 100mm PD driver pulley driving a 250mm PD driven pulley. V₂ = 1,440 × (100 ÷ 250) = 576 RPM at the driven shaft. For more worked examples and the inverse calculation (sizing pulleys for a target RPM), see our pulley speed ratio calculator.

Multi-Groove & Banded Pulleys

Drives above roughly 15kW typically use multiple V-belts running side-by-side in a multi-groove pulley — sharing the load and giving redundancy if a belt fails. AIMS stocks multi-groove taper-lock pulleys across SPA/A, SPB/B and SPC/C sections (up to 6, 10 and 12 grooves respectively).

For shock loads, frequent reversing or limited fitting space, banded V-belts (multiple V-belts bonded together at the top) provide a single-piece drive that won't whip or tangle. Banded belts run in standard multi-groove pulleys of the matching section — AIMS stocks Gates Predator banded belts and Gates Predator single belts as the matching belt range for mining, quarry and heavy-shock applications; pair them with the multi-groove pulleys above.

Selection Criteria

Working through a V-pulley spec, in order:

1. Belt section — must match the belt exactly (Z/SPZ/A/SPA/B/SPB/C/SPC/D/E).
2. Number of grooves — driven by total drive power and belt service factor.
3. Pitch diameter — drives speed ratio and centre distance. Respect the minimum PD for the belt section.
4. Bore type — pilot, taper-lock, Mi-Lock or (to order) keyed solid bore. Drives install/removal labour cost.
5. Material — cast iron default; aluminium for light-duty/low-mass; steel for special cases.
6. Speed rating — confirm the pulley is rated above operating RPM. Cast iron pulleys are typically rated to around 6,500 surface metres per minute.
7. Balance grade — for any drive above roughly 1,800 RPM, request manufacturer balance certification (typically G6.3 per ISO 1940 for general industrial use).

Pulley Wear & Replacement

Worn pulley grooves are the single most common cause of premature V-belt failure. Check groove condition with a V-belt groove gauge at every belt change — if the gauge shows the groove walls are no longer flat, or if the belt sits at or below the top of the groove (rather than slightly above it), the pulley is worn.

Critical: Never fit a new V-belt to a worn pulley. The new belt's softer compound conforms to the worn groove geometry within hours, accelerating wear on both belt and pulley. Replace the belt and the pulleys as a set whenever the gauge shows groove wear. Skipping this step is false economy — new belt life on a worn pulley is typically 10–20% of design life.

Other replacement triggers: visible cracking in the pulley rim or hub, scored or galled bore (taper-lock and Mi-Lock pulleys), broken keyway corners, runout above 0.2mm TIR at the rim. For systematic V-belt drive troubleshooting see our V-belt problems and solutions guide. For storage and shelf-life of replacement belts, see our belt storage and handling guide.

Australian & International Standards Reference

• AS 2784-2002 — Endless wedge belt and V-belt drives. Industry guidance on selection, installation and tensioning.
• ISO 4183:1995 — Belt drives, classical and narrow V-belts: grooved pulleys (datum width system) — pulley groove dimensions.
• ISO 4184 — Belt drives, classical and narrow V-belts: lengths in datum system.
• AS 1830 — Grey cast iron grades (typical pulley material specification).
• ISO 1940 — Mechanical vibration: balance quality requirements for rigid rotors.

Brand Range at AIMS

AIMS Industrial's V-pulley range is supplied by Finer Power Transmissions — pilot bore, taper-lock and Mi-Lock (Bi-Loc) configurations in cast iron and aluminium, across the SPZ/Z to SPC/C sections, dimensioned to the ISO 4183/4184 system.

For the matching belts on a multi-belt or heavy-shock drive, see the Gates range, including Predator single belts and Predator banded belts — these run in the multi-groove pulleys above and are a common heavy-duty pairing in mining and quarry drives.

Companion Components

A V-belt drive is a system. The matching components in stock at AIMS:

• Industrial V-belts — classical and narrow sections to match every pulley groove profile.
• Belts (full range) — V-belts, timing belts, banded, FRAS and specialty.
• Taper-lock bushes — Fenner-pattern bushes for taper-lock pulleys.
• Timing pulleys — for synchronous (toothed) drives.
• Idler pulleys — flat-face and grooved tensioner pulleys.
• Pulleys (parent range) — full pulley range including V, timing and idler.
• Sprockets — for chain drives where a V-belt is not the right choice.
• Couplings — for direct-drive applications.
• Key steel — broached keyways need matched key steel.
• Shaft collars — for axial positioning on the shaft.

AIMS' Note on V-Pulley Selection

If you're matching a replacement pulley to an existing drive, what we need is simpler than it looks:

• Belt section (printed on the side of the existing belt — e.g. SPB, A, SPC2500 etc.)
• Number of grooves
• Pitch diameter (or outside diameter — we can convert)
• Shaft diameter
• Bore type (pilot, taper-lock, Mi-Lock, or keyed solid to order)

If you're speccing a new drive: motor power and RPM, target driven RPM, driven shaft diameter, centre distance available, and any environmental factors (high temperature, oil exposure, dust, FRAS requirement). If you're weighing a belt drive against a chain drive for the same application, our belt vs chain drives guide runs through the trade-offs.

Need help speccing a V-pulley or matching a replacement to an existing drive? Call (02) 9773 0122 or contact our team — we'll work through belt section, drive geometry, bore configuration and stocked options with you.

V-Pulleys — Frequently Asked Questions

Q: What are the main bore types available for V-belt pulleys?

V-pulleys are generally available in pilot bore, keyed solid bore, taper-lock bore and (on some ranges) proprietary systems like Mi-Lock. Pilot bore pulleys are supplied with an undersized bore for workshop machining to the exact shaft size. Keyed solid bore pulleys come finish-bored to standard shaft sizes with a keyway already cut. Taper-lock pulleys accept a separate taper-lock bush to suit a range of shaft sizes. AIMS stocks pilot bore, taper-lock and Mi-Lock configurations, with keyed solid bore available to special order.

Q: What is a taper-lock bush and what are its advantages?

A taper-lock bush is a split, tapered sleeve that fits inside a matching taper in the pulley bore. Grub screws draw the bush into the taper, clamping it onto the shaft. The system allows one pulley to accept many different shaft sizes by changing the bush; installation and removal are quick without withdrawing the shaft; and the self-centring taper maintains concentricity. These features reduce maintenance labour significantly over the life of the drive.

Q: What is a Mi-Lock (Bi-Loc) pulley and how does it differ from taper-lock?

Mi-Lock (also sold as Bi-Loc) is an alternative proprietary bore-locking system stocked by AIMS on some pulley ranges. Like taper-lock, it uses a separate numbered bush (No.1, No.2 etc.) rather than a fixed finished bore, so one pulley can suit several shaft sizes. The bush profile and numbering are specific to the Mi-Lock/Bi-Loc system and are not interchangeable with Fenner-pattern taper-lock bushes — check which system an existing pulley uses before ordering a replacement bush.

Q: When should aluminium pulleys be used instead of cast iron?

Aluminium pulleys are lighter and better suited to applications where reducing rotating mass improves dynamic response — fans, blowers, and lighter-duty drives where weight matters. Cast iron pulleys have greater mass and are preferred for heavier industrial drives, where the flywheel effect of a heavier pulley smooths drive torque and resists belt slippage under shock loads.

Q: Why does minimum pulley diameter matter for V-belts?

Running a V-belt on a pulley smaller than the belt manufacturer's recommended minimum causes excessive bending around the pulley, generating heat, fatiguing the cord, and significantly shortening belt life. Each belt section has a minimum pitch diameter — smaller pulleys require either a different (narrower) belt section or a drive redesign, not just a tighter belt.

Q: What's the difference between pitch diameter and outside diameter on a V-pulley?

Pitch diameter (PD) is the diameter at the belt's neutral axis inside the groove, and is the figure used for speed ratio, belt length and drive design calculations. Outside diameter (OD) is simply the physical outer edge of the pulley, used for clearance and guarding — never for drive calculations. Quoting OD instead of PD is a common cause of speed-ratio errors when ordering a replacement pulley.

Q: What causes V-pulley groove wear and how can you detect it?

Groove wear occurs when abrasive dust, poor belt tension (causing slip), or belt misalignment erodes the groove flanks. Worn grooves allow the belt to ride lower, reducing belt life and drive efficiency. Detection: a V-belt groove gauge, a straight edge across the groove, or visual inspection showing the belt sitting below the pulley rim. Worn pulleys should always be replaced at the same time as new belts — fitting a new belt on a worn pulley immediately shortens the new belt's life.

Q: What power range does a Z/SPZ belt section handle compared with an A/SPA section?

As a general guide, Z/SPZ carries roughly 0.5–4kW, suited to fractional-kW motors and light workshop drives, while A/SPA carries roughly 2–11kW, suited to HVAC fans, small compressors and workshop tools. Always confirm against the belt manufacturer's current rating tables for a specific drive.

Q: Can a classical V-belt section run in a narrow-section pulley groove?

No — narrow sections (SPZ, SPA, SPB, SPC) and classical sections (Z, A, B, C, D, E) use different groove geometry and are not interchangeable, so a mismatched belt will sit incorrectly in the groove and fail prematurely.

Q: When are multi-groove or banded pulleys used instead of a single V-belt?

Drives above roughly 15kW typically use multiple V-belts side-by-side in a multi-groove pulley for load sharing and redundancy, while banded belts (bonded together at the top) suit shock loads, frequent reversing or limited fitting space — both run in the same multi-groove pulley of the matching section.

Q: How many grooves does my drive need?

Groove count is set by total drive power, the power-per-belt rating of the chosen section (see the table above), and the belt manufacturer's service factor for your duty cycle and shock loading. As a working method: take total drive kW, apply the manufacturer's service factor, divide by the power-per-belt rating for the section, and round up to the nearest stocked groove count (AIMS stocks 1 up to 6, 10 or 12 grooves depending on section).

Q: Why does a V-pulley need balance certification on high-RPM drives?

For any drive above about 1,800 RPM, manufacturer balance certification (typically G6.3 per ISO 1940) should be requested to keep vibration within acceptable limits and protect bearings and shaft seals from premature wear.

Q: What Australian standard covers the grey cast iron grade used in V-pulley manufacture?

AS 1830, which sets the grey cast iron grades commonly specified for pulley castings.

Q: What information do I need to order a replacement V-pulley?

Belt section (printed on the side of the existing belt), number of grooves, pitch diameter or outside diameter, shaft diameter, and bore type preference (pilot, taper-lock, Mi-Lock, or keyed solid to order). Our team can convert between PD and OD if only one is known.