Precision worm and worm wheel engineered for Korean industry.
Korea Ever-Power Worm And Worm Wheel Co.,Ltd manufactures a full catalogue of worm drive components — from Ø5 mm micro-modules to Ø300 mm industrial worm wheels — shipped out of Ansan to OEMs across Korea, Japan and Southeast Asia since 2015.
What are worm gears, exactly?
A worm gear is a right-angle power transmission where a threaded cylindrical shaft — the worm — drives a toothed wheel whose teeth wrap obliquely around its circumference. Each turn of the worm advances the wheel by one tooth, which means a single-start worm meshing with a 40-tooth wheel delivers a 40:1 reduction in one compact stage. No other parallel-shaft gearing achieves that ratio density in the same envelope. The main components of a worm gear system reduce to just two engineered parts: the worm shaft on the input side, and the worm wheel on the driven side.
Two behaviours set this drive apart. First, the worm can drive the wheel freely, but the wheel — in most shallow-lead geometries — cannot back-drive the worm. This self-locking behaviour is what puts these drives inside hoists, lifts, antenna positioners and conveyors where the load must stay put when power is off. Second, the tooth contact is a sliding contact, which is quiet and vibration-damping but also the reason lubrication selection matters more here than for a spur gear. Understanding worms and worm wheels starts with that single observation: sliding contact, not rolling contact, governs everything about the drive's behaviour.
A brief note on terminology. "Worm drive" and "worm gear" are used interchangeably in engineering practice, while "worm gearbox" or "worm gear reducer" refers to a complete sealed assembly that includes the worm-and-wheel pair plus housing, bearings and shaft extensions. Our catalogue covers all three categories — loose components, complete reducers, and motor-ready gearboxes — so Korean OEMs can buy at whichever level of integration suits their assembly line.
Anatomy at a glance
Hover the numbered hotspots on the photo to see the name of each feature. The four callouts cover the elements most frequently misidentified on first-year drawings — especially the lead angle, which is drawn on the worm but measured as the spiral's slope relative to the shaft's radial plane.
The self-locking property
Shallow lead angles (below ~5°) produce static friction high enough that the wheel cannot back-drive the worm. This is a safety feature on lifts and an engineering trade-off on efficient drives — you cannot usually have both in the same set.
Non-throat, single-throat, and double-throat worm gears.
Three geometries — the different types of worm gears most commonly specified — cover nearly every drive in service today: non-throat, single-throat, and double-throat. The choice between them is driven mainly by how much the wheel teeth wrap around the worm — more wrap means more tooth pairs in contact at any moment, which raises load capacity at the cost of machining complexity. A rough rule we give first-time Korean customers: pick non-throat for cost-driven light drives, single-throat for 80 % of industrial work, and double-throat only when torque density is the deciding factor.
Non-throat worm gears
Cylindrical worm meshing with a cylindrical wheel — the wheel face is straight-cut, not throated around the worm. Only one or two teeth engage at any time, so load capacity is the lowest of the three types, but tooling is simple and replacement wheels are trivial to cut.
Typical: light-duty indexing, instrument drives, office electronics
Single-throat worm gears
The worm stays cylindrical but the wheel is hobbed with a concave throat that wraps partially around the worm. Three to four teeth sit in mesh at any time — the contact pattern is a short line rather than a point. This is the worm gear type you will see most often in industrial reducers, hoist drives, and machine-tool C-axis applications.
Typical: industrial reducers, hoist drives, CNC C-axis
Double-throat (double-enveloping) worm gears
Both the worm and the wheel are throated — the worm takes on an hourglass shape that wraps around the wheel's teeth. Six to eight teeth engage simultaneously. Load capacity per unit envelope is two to three times a single-throat set. The trade-off: machining demands a specialised hob for each ratio, so lead time and unit cost both rise.
Typical: heavy hoists, military, high-torque servo drivesHow do worm gears work — step by step.
The worm drive converts rotary input on the worm shaft into slower, higher-torque rotary output on the worm wheel. Because the worm and wheel axes sit at 90° to each other, the motion transfer also changes shaft direction in a single stage. The five-step walkthrough below is the shop-floor explanation our engineering desk uses when a new Korean customer asks how worm gears work in practice rather than in theory.
Input at the worm shaft
The motor, hand-wheel, or upstream gear turns the worm at its rated rpm — typically 500 – 3000 rpm for industrial drives.
Thread engages wheel tooth
Each rotation of the worm advances one tooth of the worm wheel for a single-start worm, two teeth for a double-start worm, and so on.
Sliding contact transfers force
Contact between worm flank and wheel tooth is primarily sliding, which is why a worm gear needs a dedicated lubricant envelope — not the same oil as a spur reducer.
Torque multiplication at the wheel
Output torque scales roughly with the ratio minus friction losses. A 40:1 set with 85 % efficiency delivers 34 × the input torque at the wheel.
Self-locking holds the load
When input power stops, a shallow-lead worm cannot be back-driven by the load on the wheel — the drive holds position without a brake.
Worm gear ratio and calculation
The worm gear ratio is determined by a single equation: reduction ratio = worm wheel teeth ÷ worm thread starts. Try the live calculator below — change either number and the reduction updates instantly. Engineers often use this to sanity-check a quote before drawing the housing envelope.
The two halves of any worm gear set.
Every drive of this kind, regardless of manufacturer or catalogue size, reduces to two engineered components: the worm (also called worm shaft or drive screw) and the worm wheel (also called worm gear). Getting the pair right is the entire design game — dimensioning one without the other almost always produces a drive that runs noisily or wears quickly. A hard-earned rule from our engineering desk: specify the wheel first (material, tooth count, accuracy class), then derive the worm geometry from the wheel specification rather than the other way around. This approach keeps the wheel — the part that wears and gets replaced — within standard catalogue sizes, which cuts replacement lead time in half over the drive's service life.
01The worm (worm shaft)
A cylindrical shaft machined with one, two, three, or four helical threads — called "starts". The number of starts sets the ratio together with the wheel tooth count. Hardened alloy steel (SCM415, 20CrMnTi) is standard for the shaft because the sliding contact demands a hard flank to avoid scuffing.
- MateryalSCM415 / 20CrMnTi
- Katig-a58–62 HRC (case)
- Starts available1, 2, 3, 4
- Surface finishRa 0.4 µm (ground)
02The worm wheel
The driven wheel with oblique teeth that match the worm's helix. Bronze is the traditional wheel material because it is softer than the hardened worm — the softer material absorbs the sliding wear, which keeps the expensive hardened shaft reusable across several wheel replacements. Alloy steel and plastic wheels are also common in niche duty.
- MateryalTin bronze / Al-Fe bronze
- Katig-a65–90 HB
- Tooth countZ20 – Z120 standard
- Accuracy gradeDIN 5 – DIN 7
What materials are worm gears made from?
Five material families cover almost every worm gear in service. The pairing rule experienced engineers follow: hard worm shaft on softer worm wheel, with a hardness ratio of roughly 2:1 between the two. The softer wheel absorbs the sliding friction and wears preferentially, which protects the more-costly hardened worm shaft across several wheel service lives.
| Worm & Wheel material | Load capacity | Corrosion resistance | Best fit |
|---|---|---|---|
| Tin bronze wheel + alloy steel worm | General industrial drives, machine tools | ||
| Aluminium-iron bronze wheel + SCM415 worm | Hoists, heavy conveyors, 24/7 duty | ||
| Stainless 316 wheel + stainless 304 worm | Food, pharma, marine environments | ||
| Ductile cast iron wheel + 40Cr worm | Heavy slow drives (cement, mining) | ||
| PA66 nylon wheel + POM worm | Office electronics, micro-instruments |
Bar lengths are relative scoring against the strongest option in the same column; not absolute engineering values.
Every catalogue worm gear set we list is available in at least three of these material pairs as a standard order — custom pairings outside this list are quoted individually with an engineering review. For high-volume production programmes, our metallurgy desk can also source custom bronze alloys from Korean and Japanese foundries when the specification demands something beyond the standard catalogue grades.
Worm gear mounting methods — keyway, set screw, split.
A worm wheel can be fixed to its shaft by one of three standard mounting methods — keyway, set screw, or split hub. The choice is driven mainly by transmitted torque, assembly access, and how often the wheel needs to come off in service. Engineers often settle the mounting question after the material pair has been chosen — the three methods below each handle a different combination of load and serviceability.
Keyway
A rectangular slot cut into both the shaft and the wheel bore receives a matching steel key. The key transmits all torque by shear — no friction at all between bore and shaft. This is the highest-torque mounting method available and also the one that tolerates the most thermal cycling. The downside: removing a keyed wheel after years of service can be difficult if the bore has corroded onto the shaft.
Set screw
A threaded fastener through the wheel hub bears down on a flat machined into the shaft. Torque is transmitted by friction plus the indent the screw makes in the shaft flat. The method is cheap and fast to install, and the hub does not need an expensive keyway broaching operation — which is why it dominates in catalogue worm wheels for small drives.
Split hub (clamp)
The wheel hub is slit radially and closed around the shaft by two or four clamp bolts. No shaft machining is required — the wheel locates purely by frictional grip. Repositioning is easy, which makes split-hub mounting the preferred choice on prototype and low-volume machines where the design may still iterate. The clamp force does require larger hub diameter, so split is not always the right answer in tight envelopes.
Why Korean OEMs route worm gear orders through Ansan.
Korea Ever-Power Worm And Worm Wheel Co., Ltd operates a dedicated worm gear and worm wheel production line inside the Ansan industrial zone. The facility is specialised — no spur or helical gearing comes off these lines — which keeps the engineering knowledge deep and the setup time between catalogue sizes short. Four things differentiate the Ansan operation from the larger tier-1 Japanese suppliers Korean buyers usually compare against.
catalogue items ship in 25 business days — 60 % shorter than the 8-week Japanese tier-1 average on equivalent specifications
prototype batches from 2 pieces, production runs from 10 — useful when the customer is still iterating a design
full range in-house; DIN 5 rotary-table grade ground after heat treatment on Reishauer profile grinder
drawing reviews and quotations in Korean within one working day; Japanese and English also supported
Ever-Power is registered as Korea Ever-Power Worm And Worm Wheel Co., Ltd at Sandan-ro, Danwon-gu, Ansan-si, Gyeonggi-do. The production floor runs on an ISO 9001:2015 quality system with IATF 16949-aligned procedures for automotive tier-1 programmes. Contact the engineering desk at [email protected] — drawings are reviewed under NDA before any quotation leaves the office.
Featured worm gear products.
Six flagship worm gear products below cover the most-shipped categories out of the Ansan line — stainless for CNC, alloy steel for automotive, duplex for zero-backlash precision, cylindrical for general industrial, brass for micro applications, and plastic for instrument drives. Each card links to the full product page with parameter table, material options, and enquiry details.
Stainless Steel Worm Gear
DIN 5 – DIN 7 accuracy for CNC rotary tables and machine-tool C-axis drives. 304/316 stainless for corrosive environments.
Alloy Steel Worm & Gear
SCM415 / 20CrMnTi carburised & ground for EPS, EPB, and seat-actuator programmes. IATF 16949-aligned.
Duplex Worm Gear Set
Axial-shift worm with variable tooth thickness eliminates backlash by 30 – 40 % over standard catalogue sets.
Cylindrical Worm Wheel
Single-throat cylindrical pair, the industrial workhorse — bronze-on-steel for 80 % of general drive applications.
Brass Worm Wheel & Shaft
Micro-module brass wheel with matched steel worm shaft for instrument drives, office electronics, and medical devices.
Plastic Worm Gears
Engineering-grade POM and PA66 wheels for silent-running, low-load applications — office equipment, toys, consumer goods.
Where worm gears earn their keep.
The common applications of worm gears span every corner of industrial life — wherever a design needs big reduction in a small envelope, quiet operation, or the ability to hold load without a brake. The four industry panels below cover roughly 70 % of the drives we ship from Ansan each quarter. Outside these four, we also ship regular volumes into medical imaging equipment, theatre lighting rigs, wind-turbine yaw and pitch drives, solar tracker actuators, and professional broadcast pan-tilt heads — all applications where the combination of high ratio, silent operation and self-locking capability simply cannot be matched by a competing gear family.
Electric power steering, seat recline motors, wiper drives, parking brake actuators — the 20CrMnTi-on-bronze pair dominates here, typically DIN 6 accuracy with IATF 16949 documentation.
5-axis rotary tables, ATC magazines, C-axis drives on CNC lathes — DIN 5 to DIN 7 accuracy depending on position. Ground teeth on the wheel are standard for rotary-table duty.
Self-locking worm drives hold the load when power is cut — eliminates the separate brake that a helical gear drive would need. Single-start worm with sub-5° lead is the defining feature.
Low-rpm output and quiet running make the worm gear the standard choice for packaging lines and food conveyors. Stainless material pair preferred for wash-down compatibility.
Advantages, limitations, and lubrication.
Every gear family carries trade-offs. These drives are excellent at some jobs and genuinely the wrong choice at others. The honest balance sheet below is what our engineering desk walks Korean designers through during the first specification call. We recommend working through both columns before committing to a design — half the applications that start the enquiry as "we need a worm gear" end up better served by a helical or planetary stage, and saying so costs us a sale in the short term but builds the kind of trust that generates five repeat orders over the next three years.
Advantages of worm gears
- Big reduction in one stage. 20:1 up to 300:1 without stacking planetary stages.
- Self-locking capability. Holds load without a separate brake when lead angle is below about 5°.
- 90° shaft arrangement. Changes direction and reduces speed in the same component.
- Quiet and smooth. Sliding contact produces lower noise than any parallel-shaft alternative.
- Shock absorption. The sliding interface acts as a damper against cyclic torque spikes.
- Compact envelope. Ratio density per unit volume is the highest of any gear family.
Limitations of worm gears
- Lower efficiency. Sliding contact loses 10 – 50 % depending on ratio and lubrication — far more than a spur or helical.
- Heat generation. The same sliding that delivers quiet running also produces heat that must be carried away by the oil.
- Not reversible (by design). Self-locking is a feature, but it means the wheel cannot drive the worm in a shallow-lead set.
- Lubricant-sensitive. Worm drives need dedicated gear oils — ISO VG 220 or 460 synthetic is typical; standard hydraulic oil is not enough.
- Wheel wear is the life-limiter. The softer bronze wheel wears preferentially — expect to replace the wheel once or twice over the worm shaft's life.
- Unit cost per Nm. For the same output torque, a helical stage is typically 15 – 30 % cheaper than a worm drive.
Worm gear lubrication at a glance
Worm gear lubrication selection depends on sump temperature, worm rpm and load. The table below shows the ISO VG grade our engineering desk typically recommends for each combination — treat it as a starting point, not a final specification. Drives running outside these conditions, or drives with unusual duty cycles, deserve an individual lubrication review before the first oil fill. Getting the viscosity grade right is the single most impactful service-life decision on any worm gear set — a two-grade mismatch can halve expected bearing and flank life.
| Sump temperature | Low load (≤30 % rating) | Medium load | Heavy load (≥80 %) |
|---|---|---|---|
| Below 40 °C | ISO VG 150 | ISO VG 220 | ISO VG 320 |
| 40 – 70 °C | ISO VG 220 | ISO VG 320 | ISO VG 460 |
| 70 – 90 °C | ISO VG 320 | ISO VG 460 | ISO VG 680 synth |
| Above 90 °C | ISO VG 460 synth | ISO VG 680 synth | Forced cooling |
Synthetic polyalphaolefin (PAO) or polyglycol (PAG) oils are preferred for sump temperatures above 70 °C — mineral oils oxidise too quickly in that range. Polyglycol oils give slightly lower friction on sliding contact and can extend service life by 30 – 50 % at elevated temperature, but they are not compatible with every seal material — consult our engineering desk before retrofitting PAG into a drive originally specified for mineral oil.
⚠Three common failure modes to watch for
Knowing how these drives fail is half the battle in designing one that lasts. The three failure modes below account for roughly 85 % of warranty returns across our Korean customer base — recognising them early lets the maintenance team plan a scheduled replacement instead of a line-stop emergency.
Small surface pits from repeated contact stress. Expected over long life; if they appear early, the drive is overloaded or the lubricant film is too thin.
Longitudinal score marks from momentary metal-to-metal contact. Caused by lubricant starvation, wrong viscosity, or contamination.
Sudden catastrophic failure. Caused by shock overload or fatigue after prolonged operation outside the dimensioned service factor.
How to select the right worm gear — in seven questions.
The seven questions below cover every piece of information our engineering desk needs to quote a worm gear set or worm gearbox. Work through them before the first email — doing so typically cuts the quotation cycle from four days to under one.
