PB2 APPLICATIONS

STANDARD
INDUSTRIAL

Phosphor bronze PB2 (CuSn12) centrifugal-cast worm wheels are the standard for industrial conveyor drives, industrial gearbox NMRV/NMR series, packaging machine worm drives, material handling drives, textile machinery drives, elevator auxiliary drives, and all worm gear applications below 100 kW at continuous duty. PB2 is compatible with all standard industrial gear oil types (GL-4, GL-5, synthetic PAO, polyglycol) without restriction — making it the lowest-complexity specification choice. Annual production volume at Korea Ever-Power is the highest of any worm wheel material, with standard sizes held in stock for same-week delivery. Standard worm wheels for SEW-Eurodrive SA/SK/R series, Nord Drivesystems, Motovario NMRV series, and all GB/T standard worm gearbox series are stocked in PB2 and available without minimum order quantity for replacement supply. The primary limitation of PB2 is its relatively modest tensile strength (230–270 MPa) — it is not suitable for shock-loaded applications such as crusher auxiliary drives or for continuous duty above 100 kW without a size penalty that may make AB2 the more economical choice at larger centre distances.

AB2 APPLICATIONS

HEAVY DUTY
INDUSTRIAL

Aluminium bronze AB2 (CuAl10Ni5Fe4) centrifugal-cast worm wheels are specified for high-duty industrial applications where PB2’s load rating is insufficient at the available centre distance: overhead crane hoists above 10 tonne lift capacity, heavy material handling conveyors above 100 kW, marine bow thruster worm gears, mining equipment auxiliary drives, and large press and injection moulding machine hydraulic pump drives. The AB2 worm wheel’s 35–50% higher contact fatigue resistance vs PB2 allows the worm gear pair to transmit the same power in a smaller centre distance — in some cases avoiding the need for a larger gearbox frame size that would be required if PB2 were specified. The mandatory compatibility check between AB2 and the gear oil is the primary complication — Korea Ever-Power supplies AB2 worm wheels with a lubricant compatibility data sheet confirming which specific oil grades have been tested and confirmed compatible with the supplied AB2 alloy batch.

SPECIALTY

CORROSION &
FOOD GRADE

Nickel silicon bronze (CuNi2Si, C64700) and duplex (bimetal) worm wheels with a steel hub and a bronze rim bonded by centrifugal casting are the two specialty options for demanding corrosion or cost contexts. Nickel silicon bronze combines the corrosion resistance of a copper-nickel alloy with higher strength than PB2, making it suitable for food processing, chemical plant, and marine worm gear applications where the combination of corrosion exposure, NSF H1 lubricant compatibility, and moderate-to-high load rating is required. Duplex (bimetal) worm wheels — steel hub shrink-fit or centrifugal-bonded with a bronze rim — are the most economical solution for large worm wheels above 400 mm OD where a solid bronze wheel would require an excessively large and expensive casting, but where the full load rating of solid bronze is still required at the tooth contact surface. Korea Ever-Power manufactures duplex worm wheels with centrifugal-bonded PB2 or AB2 bronze rims on steel hubs up to 1,200 mm OD for large industrial worm gear applications. See also: worm gear reducer selection guide for worm gear centre distance and ratio optimisation for heavy industrial drives.

Q 01

How do I identify whether my failed worm wheel is PB2 or AB2 bronze when ordering a replacement, if the original specification is unknown?

Identification of the bronze alloy from a failed worm wheel can be performed by three methods in ascending order of certainty: (1) Visual colour identification: PB2 phosphor bronze has a distinctly reddish-gold to pale gold colour (similar to copper), while AB2 aluminium bronze has a distinctly yellowish-gold to yellow colour (similar to brass). This method gives a confident answer in approximately 70% of cases — in well-worn wheels where the colour is obscured by oil staining, the other methods are needed. (2) Hardness test: PB2 phosphor bronze Brinell hardness is 75–100 HB; AB2 aluminium bronze is 150–200 HB — approximately double. A simple Brinell or Rockwell surface hardness test on the wheel hub face (not the tooth surface, which has different hardness from wear) will distinguish PB2 from AB2 reliably. A workshop Rockwell B test result below 60 HRB = PB2; above 80 HRB = AB2. (3) Chemical spot test: a drop of 10% hydrochloric acid on the freshly machined surface of PB2 releases a faint smell of hydrogen sulfide (from the tin-sulfide phase in phosphor bronze); AB2 shows no such reaction. This is a confirmatory test, not a primary identification method. When ordering a replacement worm wheel and the material is uncertain: if the gearbox is a standard catalogue frame size (NMRV, K series, WP series, etc.), Korea Ever-Power can identify the original material from the gearbox type designation and size. If the gearbox is custom or non-standard, specify the application duty (power, speed, duty cycle) and Korea Ever-Power will recommend the correct bronze grade.

Q 02

My worm wheel is showing progressive pitting on the tooth flanks — is this a material problem, a lubrication problem, or a load rating problem?

Bronze worm wheel tooth flank pitting requires root cause identification before replacement — if the replacement wheel is the same material and operating under the same conditions, it will fail at the same rate. Root cause diagnosis by pitting pattern and rate: (1) Rapid pitting within 500 hours at rated load (material problem): the bronze alloy is incorrect for the application duty — either PB2 in a duty that requires AB2, or a sand-cast wheel where centrifugal cast is required. The pitting initiates at porosity or inclusion sites in the sand-cast rim and propagates rapidly. Remedy: replace with centrifugal-cast wheel of the same or upgraded alloy, confirm centre distance and alignment. (2) Progressive pitting after 5,000–15,000 hours (wear end-of-life): normal fatigue failure at the end of the design life. The wheel has run its useful life; replacement with the same specification is appropriate. Examine the worm shaft thread surface — if the worm thread shows glazing or wear lines, the worm shaft should be replaced or re-ground simultaneously with the wheel to restore the hardness differential. (3) Edge pitting on one side of the tooth face (lubrication or alignment problem): pitting concentrated at one tooth face end indicates misalignment between worm and wheel axes, or inadequate face-width contact due to worm shaft deflection at rated load. Check worm shaft deflection at maximum rated torque — should not exceed 0.05 mm at the worm thread centre. (4) Uniform thin layer of surface material removed (oil-related pitting): caused by inadequate EHL film from incorrect oil viscosity (too low), contaminated oil, or overheated oil above 80°C. Drain and refill with correct ISO VG grade; if oil temperature exceeds 80°C at full load, upgrade to the next higher viscosity grade.

Q 03

What is the minimum order quantity and lead time for custom bronze worm wheels at Korea Ever-Power, and can I order a single replacement piece?

Korea Ever-Power operates three supply tiers for bronze worm wheels with different MOQ and lead time structures: (1) Stock worm wheels (common NMRV, K-series, WP-series sizes in PB2): MOQ 1 piece, immediate dispatch from Korea Ever-Power’s Hangzhou warehouse within 2 working days. These cover the 30 most common worm wheel sizes used in standard catalogue gearboxes. (2) Made-to-order standard sizes (PB2 or AB2, OD 50–300 mm, standard gear geometry): MOQ 3 pieces, lead time 10–18 days. For MOQ 1 piece on made-to-order: lead time 15–22 days (single piece incurs higher setup cost per piece but is supplied without MOQ restriction). (3) Large custom worm wheels (OD above 300 mm, duplex bimetal, or specialty alloy): MOQ 1 piece, lead time 20–35 days depending on size and alloy. For emergency replacement of a failed worm wheel causing production line downtime, Korea Ever-Power can prioritise production of a single replacement wheel ahead of batch orders — contact Korea Ever-Power’s emergency supply team directly with the wheel dimensions (OD, number of teeth, module, bore diameter and keyway, face width, and bronze grade) and the production restart deadline for availability assessment.

Spur Gears

M1–M20 · industrial · conveyor · 316L

Helical Gears

Low noise · high load · double helical

Engrenages coniques

Right-angle · spiral · industrial drive

Worm Gears

PB2 · AB2 · centrifugal cast · industrial

Ring Gears

Internal · large ring · wind · slewing

Planetary Gears

Compact · high torque density · servo

Plastic Gears

POM · MC Nylon · light worm wheel alt.