GEAR APPLICATION GUIDE · WORM GEAR · W10

Custom OEM Worm Gear Manufacturing:
Non-Standard Ratios, Special Materials and Complete Worm Gear Set Supply

The worm gear is unique among gear types in the breadth of its customisation requirements — the ratio (from 5:1 to 100:1 in a single stage), centre distance (from 25 mm to 300 mm in standard NMRV-footprint housings), number of starts (1 to 6), thread profile (ZI involute, ZA Archimedean, ZN normal), material pairing (steel worm against bronze, cast iron, or even nylon wheel), and self-locking characteristic all interact in ways that standard catalogue worm gear sets cannot always accommodate for specialist OEM machine designs. This guide covers Korea Ever-Power’s custom worm gear set manufacturing service — from non-standard ratio and centre distance through special material pairings, duplex worm designs, and large-diameter worm wheels for heavy industrial applications that have no catalogue equivalent.

20CrMnTi · 316L · PB2 · Nylon · Centre 25–300mm
Ratio 5:1–100:1 · 1–6 Starts · ZI / ZA / ZN Profile
OEM · Special Ratio · Duplex · Large Wheel · ATEX

CENTRE DISTANCE

25 – 300 mm

Korea Ever-Power custom worm gear centre distance range. 25–63 mm: instrument and light-duty auxiliary drives. 63–160 mm: standard industrial and agricultural worm gear sets. 160–250 mm: heavy industrial valve drives, solar tracker drives, stage machinery. 250–300 mm: large antenna positioning, telescope drives, mine hoist auxiliary. Above 300 mm: on request with lead time 45–60 days

RATIO RANGE

5:1 – 100:1

Single-stage worm gear ratio range. Standard catalogue ratios: 5, 7.5, 10, 12.5, 15, 20, 25, 30, 40, 50, 60, 80, 100:1. Custom non-standard ratios (e.g. 18:1, 22:1, 35:1, 45:1, 55:1): available with 5–10 day additional lead time for worm blank reprofiling. Non-standard ratios arise from OEM machine kinematic requirements that do not align with the standard NMRV ratio sequence

STARTS

1 – 6 Starts

Worm thread start count selection: 1-start for self-locking and high-ratio (60:1–100:1). 2-start for ratios 20:1–50:1 with moderate efficiency (η 55–75%). 3-start for ratios 10:1–25:1, η 65–82%. 4-start for ratios 8:1–20:1, η 70–85%. 5–6 start for ratios 5:1–10:1, η 80–90%. More starts = higher efficiency but lower max ratio and no self-lock

LEAD TIME

8 – 30 days

Custom worm gear set lead time. Standard ratio, non-standard centre distance in 20CrMnTi + PB2: 8–15 days. Non-standard ratio, standard centre distance: 12–18 days. Special material (316L stainless, ATEX bronze): 15–22 days. Duplex worm (variable lead): 20–30 days. Replacement for discontinued OEM worm gear: 10–20 days from measurement data receipt

Custom Worm Gear OEM Service — Non-Standard Designs and Specialist Applications

The worm gear’s fundamental design equation — ratio = (wheel tooth count z₂) / (worm thread starts z₁) — means that virtually any ratio is achievable by selecting an appropriate combination of z₁ (1–6) and z₂ (typically 10–100 teeth). This flexibility is both the worm gear’s greatest design advantage and the primary driver of custom worm gear demand: an OEM machine designer who needs ratio 18:1, 35:1, or 45:1 (ratios that do not appear in any standard NMRV catalogue) can only source the correct worm gear as a custom item. Korea Ever-Power’s custom worm gear service addresses exactly this need — non-standard ratios manufactured at the same quality and lead time as standard catalogue ratios, because the manufacturing process difference between a 20:1 and an 18:1 worm gear set is limited to changing the worm thread lead (programmed in the CNC thread-grinding machine) and the wheel tooth count (re-indexed on the wheel hobbing machine).

Korea Ever-Power’s custom worm gear manufacturing service covers the full range of special requirements that OEM machine builders and replacement parts customers encounter: non-standard ratios between the standard NMRV sequence values, non-standard centre distances that do not fit NMRV housing sizes, special material pairings (316L stainless worm with food-grade bronze wheel, ATEX bronze worm with brass wheel, large-diameter cast iron worm wheel for heavy industrial drives), duplex (variable-lead) worm profiles for precision positioning drives, and large worm wheels (OD above 400 mm) for stage machinery, telescope drives, and industrial turntable positioning systems. For customers selecting between custom worm gear sets for different applications, our worm gear reducer product range (worm gear reducer and worm reducer series) covers the most common standard ratios and centre distances as complete assembly units — custom worm gear sets are the appropriate choice when the standard assembly units cannot meet the specific ratio, centre distance, or material requirement.

The worm wheel material selection for custom OEM worm gear sets is a more complex decision than for other gear types, because the worm wheel material must be soft enough to conform to the worm thread profile during run-in (which improves the contact pattern and reduces noise) while being hard enough to resist the extreme sliding wear at the worm-wheel tooth contact (where the relative sliding velocity at the mesh can reach 2–5 m/s in typical industrial worm drives). The standard worm wheel material — centrifugal-cast phosphor bronze PB2 (CuSn12) — provides this balance well for mineral or synthetic gear oils at operating temperatures below 80°C. For elevated temperature operation (above 80°C oil temperature, as occurs in continuous high-ratio worm drives with inadequate cooling), the PB2 bronze’s UTS reduces from 320 MPa at ambient to below 280 MPa at 100°C — a 13% reduction in tooth bending fatigue strength. In these applications, Korea Ever-Power uses aluminium bronze (CuAl10Ni5Fe4, UTS 600 MPa at ambient, 550 MPa at 100°C) for the worm wheel, accepting the higher friction coefficient and lower running-in adaptability of aluminium bronze in exchange for the improved hot strength and heat resistance that prevents the wheel tooth surface from softening and deforming under sustained high-temperature load.

custom worm gear set OEM non-standard Korea Ever-Power
Korea Ever-Power customized worm gear set for specialist OEM application — non-standard ratio 22:1 (2-start worm, 44T wheel), centre distance 100 mm, manufactured for a stage automation positioning drive requiring 22:1 ratio for the correct scene change speed at rated motor speed of 1,400 RPM. Worm: 20CrMnTi case carburized, ZI involute thread, ground Ra ≤ 0.3 μm, thread angle 20°, lead angle at pitch point 10.2° (2-start, 100 mm centre). Wheel: centrifugal-cast PB2 phosphor bronze (CuSn12), hobbed to AGMA Q8, OD 200 mm, face width 50 mm. Calculated efficiency: 68% at rated torque (2-start worm, 22:1 ratio, μ = 0.03 at operating temperature). Non-locking (back-driving efficiency η_back = 22%) — a motor brake is specified in the stage drive design to hold position during scene changes. Full contact pattern test with running-in procedure (10 hours at 25% torque, then 100% rated torque) included in the supply package for stage automation drives where quiet operation is specified.

Custom Worm Gear Application Categories

Non-Standard Ratio OEM Supply

The most frequent custom worm gear enquiry — an OEM machine builder has a specific ratio requirement (e.g. 18:1, 22:1, 28:1, 35:1, 45:1, 55:1) that falls between standard NMRV catalogue values. Korea Ever-Power can manufacture any ratio from 5:1 to 100:1 in a single stage, with lead times comparable to standard ratio supply because the non-standard ratio requires only a CNC program change on the worm thread grinder and a different wheel blank with the required tooth count. Non-standard ratio examples: 18:1 (1-start worm, 18T wheel — borderline self-locking), 22:1 (2-start, 44T — moderate efficiency, no self-lock), 35:1 (1-start, 35T — reliable self-lock), 55:1 (1-start, 55T — self-lock, η 35%). Each is calculated for the requested centre distance and output torque before manufacture.

Any ratio 5:1–100:1 · 12–18 days lead time

Large Worm Wheel (OD > 400 mm)

Stage machinery turntables, observatory telescope slow-motion drives, industrial positioning systems, and large valve actuators occasionally require worm wheels with OD above 400 mm — sizes that no standard NMRV-format gearbox housing can accommodate. Korea Ever-Power manufactures large worm wheels up to OD 800 mm in centrifugal-cast or sand-cast phosphor bronze (PB2 for standard industrial, aluminium bronze for elevated temperature), or in ductile cast iron (for very large diameter at lower cost where the moderate friction coefficient of iron against the steel worm is acceptable). Large worm wheel hobbing: Korea Ever-Power uses a dedicated large-table CNC gear hobbing machine with 1,000 mm swing capacity, producing worm wheel tooth profiles to AGMA Q6–Q8 quality in single cuts at OD up to 800 mm. Application: theatre stage revolve drive (400–600 mm worm wheel, ratio 60:1–100:1, output torque 5,000–15,000 Nm per drive unit).

OD up to 800 mm · PB2 or aluminium bronze · 25–40 days

Replacement for Discontinued OEM Worm Sets

Many installed worm gearboxes from manufacturers who have discontinued the product (or who no longer supply the specific ratio or housing size) require replacement worm and wheel sets that are no longer available from the original source. Korea Ever-Power provides a reverse engineering service for discontinued OEM worm gear sets — the worn worm and/or wheel is submitted (or dimensional measurements provided), and Korea Ever-Power identifies the worm thread profile (ZI, ZA, or ZN) by measurement comparison, calculates the worm geometry (lead, thread angle, centre distance), and manufactures a replacement set to the identified specification. This reverse engineering service has been used for replacement of worm gear sets from Flender, Motovario, Bonfiglioli, Tramec, and many other gearbox OEMs where the specific ratio or centre distance has been withdrawn from the current product catalogue. Lead time from receipt of dimensional measurements: 10–20 days.

Any discontinued OEM · 10–20 days from measurement

brass worm wheel custom OEM Korea Ever-Power
Korea Ever-Power custom brass (CuZn38Al) worm wheel for instrument and control valve actuator application — M2.5, 30T, OD 80 mm, centre distance 50 mm, bore 25 mm H7. Brass worm wheel is used in instrument applications where the material’s lower strength is acceptable at the very low load levels (under 50 Nm output torque) and where its advantages over phosphor bronze are relevant: better machinability (lower cutting force producing better surface finish at M2.5), lower density (reducing the worm wheel inertia in high-cycle instrument drives), and non-magnetic property (required near electromagnetic sensors in control valve actuators where bronze’s copper content would be detected by the position sensor if the wheel were large). All custom worm wheel materials — PB2 phosphor bronze, aluminium bronze, brass, cast iron, MC nylon, and special alloys — are supplied with a material certificate confirming the alloy composition and mechanical properties, and the worm-wheel tooth surface finish measurement (Ra ≤ 0.8 μm standard, Ra ≤ 0.4 μm for precision positioning). Korea Ever-Power maintains alloy inventory for all standard worm wheel materials to avoid waiting for raw material procurement on small custom orders.
cylindrical worm wheel custom OEM precision Korea Ever-Power
Korea Ever-Power centrifugal-cast PB2 phosphor bronze (CuSn12) cylindrical worm wheel for custom OEM large centre distance application — M4, 60T, OD 248 mm, centre distance 130 mm, bore 60 mm H7, hobbed AGMA Q8 quality. Centrifugal casting is specified for worm wheel blanks above OD 120 mm because the centrifugal casting process produces a denser, more uniform phosphor bronze microstructure than sand casting — the improved microstructure has 15–20% higher fatigue strength and better wear resistance from the more uniform tin distribution in the bronze alloy. Korea Ever-Power maintains a range of centrifugal-cast PB2 blank ODs from 80 mm to 600 mm in standard wall thicknesses, allowing custom worm wheel hobbing to begin from a pre-cast blank without the 3–4 week lead time for a purpose-cast blank. The blank OD is turned to final dimension and the tooth profile hobbed in a single setup on Korea Ever-Power’s large-table CNC gear hobbing machine — ensuring concentricity between the bore, OD, and tooth pitch cylinder to within 0.015 mm TIR, which is critical for maintaining the designed tip clearance between the worm wheel OD and the worm shaft in the assembled gearbox.

Frequently Asked Questions — Custom OEM Worm Gears

Q 01

We need ratio 28:1 for a packaging machine indexer — no catalogue NMRV offers this ratio. Can Korea Ever-Power supply, and what is the delivery timeline for initial samples?

Ratio 28:1 is a good example of a non-standard ratio that falls between the standard NMRV 25:1 and 30:1 values — a 1-start worm with 28 wheel teeth. Korea Ever-Power supply process for this request: (1) Specification clarification (day 1–2): provide the centre distance (which NMRV housing size the worm gear must fit — or specify the centre distance if using a custom housing), the output torque, input speed, and whether self-locking is required. At ratio 28:1 with a 1-start worm at 80–100 mm centre distance, the lead angle is approximately 2.0°–2.5°, placing the drive at the borderline of self-locking (φ ≈ 1.5°–2.3° for typical operating friction). Korea Ever-Power will calculate whether 28:1 reliably self-locks for your application or whether 30:1 (firmly self-locking) would be more appropriate if self-locking is needed. (2) Quotation and sample lead time: for a 28:1 worm gear set at centre distance 80 mm or 100 mm in 20CrMnTi worm + PB2 bronze wheel (standard materials), Korea Ever-Power can deliver initial samples in 14–18 working days from order confirmation. For NMRV-footprint housing compatibility (if the packaging machine uses a standard NMRV 063 or 090 housing), the worm geometry is constrained by the housing centre distance — Korea Ever-Power will confirm the exact worm dimensions for NMRV compatibility in the quotation. (3) Volume supply from sample approval: typically 12–18 working days from sample approval, for quantities from 5 pieces to several hundred per year on a call-off basis. Packaging machine worm gear sets at non-standard ratios are a frequent request at Korea Ever-Power — we typically handle 15–25 different non-standard ratio worm gear projects per month.

Q 02

What is the difference between ZI (involute), ZA (Archimedean), and ZN (normal section) worm thread profiles, and which should I specify for a new OEM design?

The three worm thread profiles — ZI, ZA, and ZN — differ in which plane the straight tooth profile is defined, which determines the tooth geometry and the manufacturing method: (1) ZI (involute worm): the worm thread tooth profile is an involute when viewed in the axial section (cross-section through the worm axis). This is the theoretically ideal profile because the worm-wheel teeth (which are hobbed using a hob with the same geometry as the worm) have an involute form in the normal section — producing the best possible contact conditions (smooth entry and exit, consistent pressure angle across the face) at the worm-wheel mesh. ZI is the profile used by Korea Ever-Power as the standard for all ground worm threads (the involute profile can be generated accurately by a grinding wheel with a conical grinding face, making it the most practical profile for precision thread grinding). ZI is recommended for all new OEM designs where precision ground worm thread surface finish (Ra ≤ 0.4 μm) is required for efficiency and wear resistance. (2) ZA (Archimedean worm): the thread profile is a straight line in the axial section — corresponding to a helical surface with constant lead. ZA worms can be turned on a conventional lathe with a straight-edged cutting tool, making them cheaper to produce than ZI worms for low-volume or prototype applications. The mating worm wheel hobbed with a ZA-profile hob has a non-involute tooth form that performs less well under load than ZI — ZA is acceptable for low-precision, low-efficiency applications (valve handwheels, instrument drives) but not for precision or efficiency-critical drives. (3) ZN (normal section worm): the straight profile is defined in the normal to the thread helix. ZN worms are produced on hobbing machines with a tilted hob — a process used by some European gear manufacturers (particularly for large centre distances) but less common than ZI in modern precision worm gear production. Korea Ever-Power recommends ZI for all new OEM designs as the default — ZA only for low-precision, low-cost applications. If you have an existing ZA or ZN worm gear set that you need to replace, Korea Ever-Power can identify the profile from the measurement data and manufacture the replacement in the same profile system.

Q 03

We have a failed worm gear set from a discontinued Motovario gearbox, ratio 30:1, centre distance 80 mm. The worm is unusable (scoring on threads). Can Korea Ever-Power reproduce this from the wheel alone, and what information is needed from the wheel?

Yes — Korea Ever-Power can reverse-engineer a replacement worm from the existing undamaged wheel (or a wheel with only minor tooth surface wear, not deformed or broken teeth). The information required from the wheel for worm reverse engineering: (1) Wheel tooth count z₂: count the wheel teeth directly. For ratio 30:1 with a 1-start worm: z₂ should be 30 teeth. Verify by counting. (2) Wheel outer diameter (OD): measure with a micrometer at 8 positions around the circumference — the mean OD gives the approximate worm wheel reference diameter, from which the module can be estimated. (3) Wheel face width: measure the tooth face width (the dimension parallel to the wheel axis). (4) Wheel bore diameter and width: confirm the bore and keyway dimensions that the replacement worm must match the existing worm shaft. (5) Over-pin measurement of the wheel: using two pins of a known diameter placed in opposite tooth gaps, measure the distance across the pins with a micrometer. This over-pin measurement allows Korea Ever-Power to calculate the worm module (m_n), pressure angle (usually 20°), and — most importantly — the worm thread profile system (ZI vs ZA) by comparing the measured over-pin value against the theoretical values for both systems at the calculated module and tooth count. The system with the smaller deviation from the theoretical value is the original. From this information, Korea Ever-Power will identify the worm geometry, calculate the worm thread dimensions (axial pitch, lead, thread angle), and manufacture a matched replacement worm that correctly meshes with the existing Motovario wheel. Lead time from receipt of the wheel and measurements: 12–16 working days. The replacement worm is supplied with a worm-to-wheel contact pattern test confirming correct mesh before shipment.

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GET A QUOTATION · KOREA EVER-POWER

Need Custom OEM Worm Gear Sets?

Korea Ever-Power manufactures custom worm gear sets for any OEM application — any ratio 5:1–100:1 (including non-standard between catalogue values), centre distance 25–300 mm, 1–6 starts, ZI/ZA/ZN thread profiles, 20CrMnTi steel worm, PB2 phosphor bronze or aluminium bronze or brass wheel, 316L stainless, ATEX bronze, large worm wheels OD up to 800 mm. Duplex worm for sub-arc-minute backlash. Discontinued OEM worm reverse engineering. Contact pattern test certificate included. ISO 9001:2015 certified.

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