{"id":1139,"date":"2026-04-24T02:18:26","date_gmt":"2026-04-24T02:18:26","guid":{"rendered":"https:\/\/worm-and-worm-wheel.com\/?post_type=product&p=1139"},"modified":"2026-04-24T02:21:27","modified_gmt":"2026-04-24T02:21:27","slug":"duplex-worm-gear-set-dual-lead-zero-backlash-worm-drive","status":"publish","type":"product","link":"https:\/\/worm-and-worm-wheel.com\/bg\/produkt\/duplex-worm-gear-set-dual-lead-zero-backlash-worm-drive\/","title":{"rendered":"Duplex Worm Gear Set | Dual-Lead Zero-Backlash Worm Drive"},"content":{"rendered":"
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Duplex Worm Gear \u2014 What Makes It Different<\/h2>\n

A duplex \u0447\u0435\u0440\u0432\u044f\u0447\u043d\u0430 \u043f\u0440\u0435\u0434\u0430\u0432\u043a\u0430<\/strong> \u2014 also called a dual-lead worm \u2014 is a specialised variant in which the two flanks of the same worm thread are cut with slightly different modules and slightly different diameter quotients. The effect is subtle on the shop floor but decisive in the field: the tooth thickness grows steadily from one end of the worm to the other, while the gap between adjacent threads shrinks at the same rate. Shifting the worm axially inside the gearbox moves a thicker or thinner section of thread into mesh, which means backlash can be dialled in to any target value at assembly \u2014 and re-dialled later in life as the drive wears.<\/p>\n

\"Duplex<\/p>\n

On the wheel side the picture mirrors the shaft. Different modules on the two flanks produce different addendum modification coefficients and different rolling-circle diameters, so the front and rear tooth profiles of the wheel are not identical, even though the tooth thickness and tooth gap stay constant around the wheel’s circumference. The outcome is a drive that delivers single-digit-micrometre backlash when needed, and holds it through reversing service that would quickly wear out a conventional worm set. Korean machine-tool builders, rotary-indexing specialists and stamping-press manufacturers are the most frequent buyers.<\/p>\n<\/section>\n

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Technical Specifications<\/h2>\n

The values below reflect the standard catalogue envelope for duplex sets. All geometry is cut to customer drawing \u2014 duplex worms are almost never stock items because the lead-difference value itself is an application-specific parameter. Values marked “typical range” reflect industry-standard practice where the customer has not yet specified a tighter target.<\/p>\n

\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n
Parameter<\/th>\n\u0421\u043f\u0435\u0446\u0438\u0444\u0438\u043a\u0430\u0446\u0438\u044f<\/th>\n<\/tr>\n<\/thead>\n
Worm Type<\/strong><\/td>\nDual-lead (different modules on left and right flank)<\/td>\n<\/tr>\n
Backlash Range<\/strong><\/td>\n\u00b1 0.045 mm at reference tooth (adjustable down from larger values)<\/td>\n<\/tr>\n
Module Range<\/strong><\/td>\nM1 \u2013 M10 (typical range)<\/td>\n<\/tr>\n
Typical Lead Difference<\/strong><\/td>\n0.05 \u2013 0.20 mm per turn (typical range, tailored per drawing)<\/td>\n<\/tr>\n
Worm Material<\/strong><\/td>\n20CrMnTi case-hardened (HRC 58 \u2013 62) or 40Cr through-hardened<\/td>\n<\/tr>\n
Wheel Material<\/strong><\/td>\nTin bronze (CuSn10), aluminium-iron bronze (CuAl10Fe3)<\/td>\n<\/tr>\n
Tooth Finish<\/strong><\/td>\nGround after heat treatment (mandatory for duplex)<\/td>\n<\/tr>\n
Precision Grade<\/strong><\/td>\nDIN 5 \u2013 DIN 6 (standard for duplex sets)<\/td>\n<\/tr>\n
Reference Marking<\/strong><\/td>\nV-groove (60\u00b0, 0.3 mm deep) on tip of reference tooth<\/td>\n<\/tr>\n
Assembly Orientation<\/strong><\/td>\nArrow mark stamped on both worm and wheel<\/td>\n<\/tr>\n
Lead Time<\/strong><\/td>\n25 \u2013 35 business days (longer for DIN 5)<\/td>\n<\/tr>\n
Primary Applications<\/strong><\/td>\nRotary and tilting tables, CNC milling machines, presses, indexing drives<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<\/section>\n
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How the Backlash Adjustment Actually Works<\/h2>\n

Backlash on a conventional drive comes from the clearance between the mating tooth flanks at the pitch line. On a duplex set, that clearance is no longer constant along the shaft \u2014 it changes linearly from one end to the other, because the tooth thickness itself changes linearly. Shifting the shaft 1 mm axially can move backlash by 20 \u2013 40 \u00b5m on a typical M4 set, depending on the lead difference specified during design.<\/p>\n

Adjustment on assembly is a four-step process. First, the shaft is fitted to the housing with a packer or spacer set that allows a \u00b12 mm axial shift. Second, the wheel is rotated by hand while the installer feels for backlash at the output shaft. Third, the shaft is shifted axially toward the thicker-tooth end until the desired backlash is reached. Fourth, the packer set is finalised and the lock nut torqued. Re-adjusting years later, after the drive has worn, follows the same steps but typically needs only 0.5 \u2013 1.5 mm of additional shift.<\/p>\n

\"Duplex<\/p>\n<\/section>\n

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Duplex vs Other Backlash-Control Methods<\/h2>\n

Several workshop-level methods exist to reduce worm-gear backlash. Each one works, but each carries a penalty the duplex method avoids. Understanding the trade-offs is the reason design engineers specifying precision indexers pay the duplex premium willingly.<\/p>\n

\n\n\n\n\n\n\n\n\n\n
Method<\/th>\nHow It Works<\/th>\nMain Drawback<\/th>\n<\/tr>\n<\/thead>\n
Eccentric hub rotation<\/td>\nRotate the hub that cradles worm and wheel, changing centre distance<\/td>\nShifts tooth contact zone, distorts contact pattern, degrades load rating<\/td>\n<\/tr>\n
Conical worm axial shift<\/td>\nMove a tapered worm along its axis into a matching wheel<\/td>\nInterferes with geometrically correct meshing, high start-up wear<\/td>\n<\/tr>\n
Split worm (Ott system)<\/td>\nTwo worm halves rotated or shifted relative to each other<\/td>\nComplex assembly, risk of improper alignment, reduced efficiency<\/td>\n<\/tr>\n
Split wheel (two-disc)<\/td>\nTwo wheel halves rotated close to each other to preload the worm<\/td>\nHigher friction, heat rise, and wear at the preloaded contact<\/td>\n<\/tr>\n
Duplex (dual lead)<\/strong><\/td>\nAxially shift the dual-lead worm to select tooth thickness at mesh<\/td>\nHigher manufacturing cost; no geometric or wear penalty<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n

The bottom row is the only one that preserves geometrically accurate meshing after adjustment. Contact area, load capacity and efficiency are left untouched \u2014 the drive works exactly as it did before the adjustment, just at a different backlash value. That property is why duplex sets dominate the precision-indexing market despite costing 40 \u2013 60 % more than equivalent standard worm sets.<\/p>\n<\/section>\n

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Assembly Orientation and Reference Tooth Check<\/h2>\n

Because the worm and wheel have different thickness profiles on the two flanks, a duplex set is not symmetrical \u2014 it has a correct and an incorrect orientation. Ignoring this during installation causes the centre distance to sit larger than the design value, and the assembly becomes difficult or impossible to mount properly. Two pre-flight checks cover the common mistakes.<\/p>\n

Check One \u2014 Orientation Arrows<\/h3>\n

\u25b6<\/span> Both the shaft and the wheel are stamped with a small arrow at the manufacturer’s assembly mark. When fitting the pair into the housing, rotate the wheel until the arrow faces the front, then feed the shaft into engagement so that its arrow points the same direction. If the arrows point opposite, the thicker tooth is meeting the thinner tooth of the wheel and the drive will bind before it reaches the design centre distance.<\/p>\n

Check Two \u2014 Reference Tooth V-Groove<\/h3>\n

\u25b6<\/span> The tip of the duplex shaft carries a 60-degree V-groove cut 0.3 mm deep \u2014 this is the reference tooth. When the reference tooth sits exactly aligned with the rotational centre of the wheel and the centre distance is set to the drawing value “a”, the backlash sits at the design target (typically \u00b1 0.045 mm for our catalogue frames). From that starting point, axial shift is used to tune backlash up or down as the application demands.<\/p>\n

\"Worm<\/p>\n<\/section>\n

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Typical Applications for Duplex Worm Gears<\/h2>\n

Duplex sets earn their extra cost in drives where reversing accuracy must survive tens of thousands of cycles without manual re-shimming. Korean industry uses them in several distinct application niches.<\/p>\n