{"id":1594,"date":"2026-05-06T02:19:41","date_gmt":"2026-05-06T02:19:41","guid":{"rendered":"https:\/\/wormreducers.xyz\/?p=1594"},"modified":"2026-05-06T02:19:41","modified_gmt":"2026-05-06T02:19:41","slug":"nord-sk-12-vs-sk-13-worm-gearbox-replacement","status":"publish","type":"post","link":"https:\/\/wormreducers.xyz\/da\/nord-sk-12-vs-sk-13-worm-gearbox-replacement\/","title":{"rendered":"Udskiftning af Nord SK-seriens snekkegearkasse: Afkodning af SK 12 vs SK 13"},"content":{"rendered":"
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\u25e7 NORD CROSS-REFERENCE<\/div>\n

Udskiftning af Nord SK-seriens snekkegearkasse: Afkodning af SK 12 vs SK 13<\/h1>\n

Visual identification, structural differences, cross-reference equivalence tables, and the substitution mistakes that fail when replacing single-stage SK 12 with two-stage SK 13.<\/p>\n

Get a Nord Cross-Reference Quote \u2192<\/a><\/p>\n<\/div>\n<\/div>\n

Nord Drivesystems’ SK 12 and SK 13 worm gear reducer series occupy adjacent slots in the German manufacturer’s product range \u2014 and that adjacency is what creates most of the worm gear reducer cross-reference confusion. SK 12 is a single-stage worm gear reducer; SK 13 is a two-stage helical-worm hybrid that uses a helical pre-stage feeding into the worm-and-wheel output. The two units share similar mounting envelopes, similar nameplate ratings, and even similar appearance \u2014 but their internal worm gear reducer architecture, achievable ratios, efficiency curves, and cross-reference equivalents diverge substantially. The article below walks the visual identification, the spec differences, the Korean cross-reference equivalents for each, and the field mistakes that destroy production schedules. For broader cross-architecture comparison, see our companion 1-stage vs 2-stage helical-worm guide<\/a>.<\/p>\n

Why Nord SK Cross-Reference Is Trickier Than Other Brands<\/h2>\n

Nord’s SK numbering convention does not directly map onto the typical European centre-distance system used by Italian and Korean manufacturers. The “12” and “13” designate product families rather than dimensional sizes, and the actual worm gear reducer frame sizes within each family span a wide range. Understanding the family structure is the first step to specifying a correct cross-reference.<\/p>\n

A second source of confusion is that Nord SK 12 and SK 13 worm gear reducer units share an external aesthetic \u2014 both use Nord’s distinctive paint colour and flange geometry \u2014 making them difficult to distinguish without internal inspection or detailed specification reading. Engineers replacing a worm gear reducer they assumed was SK 12 sometimes specify a single-stage Korean equivalent only to discover after install that the original was actually SK 13 with a different ratio map and torque characteristic.<\/p>\n

SK 12 vs SK 13 \u2014 Side-by-Side Identification<\/h2>\n

The split-card visual below maps the architectural differences that distinguish single-stage and two-stage worm gear reducer designs in the Nord SK product family. Use the two cards as a quick reference whenever a maintenance request lists “SK” without specifying which series.<\/p>\n

<\/p>\n

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NORD<\/p>\n

SK 12<\/p>\n

Single-stage worm<\/p>\n<\/div>\n

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ARCHITECTURE<\/p>\n

Worm shaft and bronze wheel only. Direct mesh from input motor to output. Single reduction stage.<\/p>\n

RATIOS<\/p>\n

i = 5 through i = 100. Standard single-stage range.<\/p>\n

EFFICIENCY<\/p>\n

70-85% depending on ratio. Typical worm gear reducer figures.<\/p>\n<\/div>\n<\/div>\n

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NORD<\/p>\n

SK 13<\/p>\n

Two-stage helical-worm<\/p>\n<\/div>\n

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ARCHITECTURE<\/p>\n

Helical pre-stage feeds worm gear stage. Two reductions in series \u2014 input motor \u2192 helical \u2192 worm \u2192 output.<\/p>\n

RATIOS<\/p>\n

i = 25 through i = 600. Higher ratios than SK 12 single-stage.<\/p>\n

EFFICIENCY<\/p>\n

82-92% \u2014 meaningfully higher than SK 12 due to helical pre-stage.<\/p>\n<\/div>\n<\/div>\n<\/div>\n

\"Comparison<\/p>\n

Spec Comparison Matrix \u2014 SK 12 vs SK 13 Worm Gear Reducer by Frame<\/h2>\n

The two SK families overlap in some frame sizes but diverge sharply at the upper end of each. The matrix below shows the full overlap zone where engineering teams most frequently mistake one for the other.<\/p>\n

\n\n\n\n\n\n\n\n\n\n\n\n
Spec Parameter<\/th>\nSK 12 (Single-Stage)<\/th>\nSK 13 (Two-Stage)<\/th>\nSignificance<\/th>\n<\/tr>\n<\/thead>\n
Stages of reduction<\/td>\n1<\/td>\n2<\/td>\nArchitecture<\/td>\n<\/tr>\n
Available ratios<\/td>\n5 \u2014 100<\/td>\n25 \u2014 600<\/td>\nHigh<\/td>\n<\/tr>\n
Efficiency at full load<\/td>\n70-85%<\/td>\n82-92%<\/td>\nHigh<\/td>\n<\/tr>\n
Output torque (frame 100)<\/td>\n280-680 Nm<\/td>\n650-2,100 Nm<\/td>\nCritical<\/td>\n<\/tr>\n
Self-locking capability<\/td>\nYes (i \u2265 30)<\/td>\nLimited (helical reverses)<\/td>\nApplication<\/td>\n<\/tr>\n
Length envelope<\/td>\nStandard<\/td>\n+30-50 mm longer<\/td>\nMounting<\/td>\n<\/tr>\n
Heat dissipation<\/td>\nHigher (less efficient)<\/td>\nLower (more efficient)<\/td>\nThermal sizing<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n

Visual Identification \u2014 Telling SK 12 from SK 13 in the Field<\/h2>\n

When the nameplate is missing, illegible, or the snekkegearreduktion<\/a> model field is ambiguous, three external indicators distinguish SK 12 from SK 13 reliably without removing the housing.<\/p>\n

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\u25e7 INDICATOR 01 \u2014 INPUT-TO-OUTPUT AXIAL LENGTH<\/p>\n

Measure from the motor flange face to the output shaft seal. SK 13 is 30-50 mm longer than SK 12 in the same frame size due to the additional helical pre-stage in the worm gear reducer housing. On frame 80, SK 12 is typically 215 mm; SK 13 is 245-265 mm.<\/p>\n<\/div>\n

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\u25e7 INDICATOR 02 \u2014 INPUT FLANGE SHAPE<\/p>\n

SK 12 input flange transitions directly into the worm shaft housing. SK 13 input flange has an obvious intermediate cylindrical section housing the helical pre-stage gears \u2014 visible as a “stepped” profile rather than smooth taper.<\/p>\n<\/div>\n

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\u25e7 INDICATOR 03 \u2014 RUNNING NOISE SIGNATURE<\/p>\n

SK 12 produces the characteristic worm gear reducer mesh hum at fundamental and second-harmonic frequencies. SK 13 adds a higher-frequency helical mesh whine on top of the worm hum \u2014 audibly more “complex” than a single-stage unit at the same speed.<\/p>\n<\/div>\n<\/div>\n

\"WPWO<\/p>\n

Cross-Reference Tables \u2014 Nord SK to Korean Equivalents<\/h2>\n

Once SK 12 vs SK 13 is confirmed, the cross-reference equivalents follow predictable patterns. SK 12 maps onto single-stage Korean worm gear reducer families; SK 13 maps onto two-stage helical-worm equivalents.<\/p>\n

\n\n\n\n\n\n\n\n\n\n\n\n\n
Nord Code<\/th>\nFrame Size<\/th>\nKorean Equivalent<\/th>\n<\/tr>\n<\/thead>\n
SK 1Si 50<\/td>\n50 mm<\/td>\nNMRV 050 \/ WPA 50 (single-stage)<\/td>\n<\/tr>\n
SK 1Si 63<\/td>\n63 mm<\/td>\nNMRV 063 \/ WPA 63 (single-stage)<\/td>\n<\/tr>\n
SK 1Si 75<\/td>\n75 mm<\/td>\nNMRV 075 \/ WPA 80 (single-stage)<\/td>\n<\/tr>\n
SK 1Si 100<\/td>\n100 mm<\/td>\nNMRV 110 \/ WPA 100 (single-stage)<\/td>\n<\/tr>\n
SK 02050<\/td>\n50 (helical-worm)<\/td>\n2-stage helical-worm 050<\/td>\n<\/tr>\n
SK 02075<\/td>\n75 (helical-worm)<\/td>\n2-stage helical-worm 075<\/td>\n<\/tr>\n
SK 02100<\/td>\n100 (helical-worm)<\/td>\n2-stage helical-worm 100<\/td>\n<\/tr>\n
SK 02125<\/td>\n125 (helical-worm)<\/td>\n2-stage helical-worm 125<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n

Green-shaded codes: SK 12 family (single-stage worm gear reducer) \u2192 maps to single-stage Korean equivalents. Yellow-shaded codes: SK 13 family (two-stage helical-worm) \u2192 maps to Korean two-stage equivalents.<\/p>\n

Drop-In Replacement Compatibility Checklist<\/h2>\n

Six verifications confirm that the Korean cross-reference is genuinely a drop-in for the Nord original. Each step takes 5-15 minutes; the cumulative 60-90 minute check eliminates the most common substitution failures.<\/p>\n

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1<\/span>Confirm SK 12 vs SK 13 (the three indicators above)<\/p>\n

First and most important \u2014 eliminates wrong-architecture cross-reference.<\/p>\n<\/div>\n

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2<\/span>Read full Nord nameplate including ratio<\/p>\n

Format: SK 12-100\/40 or SK 02050-VR-25. Capture the trailing ratio explicitly.<\/p>\n<\/div>\n

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3<\/span>Measure foot bolt pattern and shaft height<\/p>\n

Length \u00d7 width \u00d7 bolt circle dimensions; output shaft centreline height from base.<\/p>\n<\/div>\n

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4<\/span>Verify motor flange (IEC vs NEMA)<\/p>\n

Nord SK 12\/13 typically IEC. Confirm against actual motor before finalising spec.<\/p>\n<\/div>\n

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5<\/span>Confirm self-locking requirement match<\/p>\n

SK 13 helical pre-stage may reverse \u2014 single-stage Korean equivalent recovers self-locking.<\/p>\n<\/div>\n

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6<\/span>Verify lubricant family compatibility<\/p>\n

Nord factory-fills with synthetic; Korean equivalent should be specified with same family.<\/p>\n<\/div>\n<\/div>\n

Common Mistakes When Replacing SK 12 vs SK 13 Worm Gear Reducer Units<\/h2>\n
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\u25a9 MISTAKE 01<\/p>\n

Replacing SK 13 with single-stage equivalent<\/p>\n

If the application required SK 13 ratios above i = 100, a single-stage Korean replacement cannot deliver matching output speed without changing motor speed \u2014 usually unacceptable.<\/p>\n<\/div>\n

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\u25a9 MISTAKE 02<\/p>\n

Replacing SK 12 with two-stage equivalent<\/p>\n

Reverse error. A two-stage worm gear reducer cross-reference loses self-locking that the SK 12 application may have depended on for safety holding torque.<\/p>\n<\/div>\n

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\u25a9 MISTAKE 03<\/p>\n

Forgetting the SK 13 length increment<\/p>\n

SK 13 is 30-50 mm longer than SK 12 in the same frame. Ordering a same-length single-stage replacement may not fit the existing mounting envelope when SK 13 was the original.<\/p>\n<\/div>\n

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\u25a9 MISTAKE 04<\/p>\n

Misreading the trailing ratio<\/p>\n

Nord nameplate format includes ratio after the slash; misreading SK 12-100\/40 as SK 12-100 (no ratio) leads to wrong replacement specification.<\/p>\n<\/div>\n

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\u25a9 MISTAKE 05<\/p>\n

Treating efficiency difference as cosmetic<\/p>\n

SK 13 at 90% vs SK 12 single-stage replacement at 78% means 12% more heat in the housing \u2014 may push thermal sizing into forced cooling territory.<\/p>\n<\/div>\n<\/div>\n

\"Right-angle<\/p>\n

Nord SK Worm Gear Reducer Replacement FAQ<\/h2>\n
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Q: My Nord nameplate just says “SK” \u2014 how do I tell which series I have?<\/strong><\/p>\n

A: The full Nord code lists SK followed by series identifier \u2014 SK 12 (single-stage worm), SK 13 (two-stage helical-worm), or SK 02xxx (compact two-stage helical-worm). If the nameplate is partial, use the three visual indicators (axial length, input flange shape, running noise) to confirm. If still unclear, photograph the unit and the partial nameplate and submit to our engineering team for identification \u2014 typically resolved within 24 hours.<\/p>\n<\/div>\n

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Q: Can a Korean two-stage helical-worm replace a Nord SK 12 if I want higher efficiency?<\/strong><\/p>\n

A: Mechanically yes, but consider three implications. First, the replacement worm gear reducer envelope is 30-50 mm longer \u2014 verify mounting space. Second, two-stage units may not be self-locking at all ratios \u2014 if the SK 12 was holding a load against gravity, the upgrade requires an external brake. Third, ratio range shifts upward \u2014 confirm the available ratios match the application speed requirement.<\/p>\n<\/div>\n

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Q: What is the cost difference between Korean equivalents and Nord OEM?<\/strong><\/p>\n

A: Korean cross-reference replacements typically deliver 35-55% capital cost reduction vs Nord OEM channel for SK 12 single-stage equivalents. SK 13 two-stage cross-references narrow to 25-40% reduction since the helical pre-stage adds manufacturing complexity. Lead time savings 1-2 weeks for stocked Korean equivalents vs Nord SK 13 specifically.<\/p>\n<\/div>\n

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Q: Does the Nord NSD lubricant in my SK unit need to match exactly in the replacement?<\/strong><\/p>\n

A: Match the lubricant family (PAG synthetic vs mineral CLP), not the brand. Nord NSD-class fluids are PAG synthetics; the Korean replacement should be specified with PAG synthetic from a similar viscosity grade. Brand cross-reference for Nord NSD includes Mobil SHC 600 series, Kl\u00fcber Kl\u00fcbersynth GH 6 series, and Korean-domestic synthetic equivalents. The viscosity grade (typically ISO VG 220 or VG 320) is more important to match than the brand label.<\/p>\n<\/div>\n

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Q: Are SK 12 and SK 13 mounting bolt patterns identical for the same frame size?<\/strong><\/p>\n

A: Foot bolt patterns are typically identical between SK 12 and SK 13 of the same frame number \u2014 Nord engineered the families to share the mounting envelope. Output shaft height also matches. The differences sit at the input end (axial length, flange profile) rather than the foot interface. This is helpful for cross-reference since the Korean replacement for either SK 12 or SK 13 in the same frame uses the same foot pattern, only the input\/length detail varies.<\/p>\n<\/div>\n

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Q: How accurate are the Korean equivalent torque ratings vs the Nord catalogue numbers?<\/strong><\/p>\n

A: Within \u00b15% on direct frame-and-ratio matches between Nord SK and Korean NMRV \/ WP \/ two-stage helical-worm equivalents. Korean catalogue ratings tend to slightly exceed Nord on small frames (50-75 mm) and slightly trail on heavy frames (125 mm and above). For applications where a few percent torque margin matters, request the Korean engineering team’s measured-data sheet rather than relying purely on the catalogue figure for the replacement worm gear reducer comparison.<\/p>\n<\/div>\n<\/div>\n

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Need a Specific SK Code Cross-Referenced?<\/h2>\n

Send us the complete SK code, a photograph of the existing unit and nameplate, the application context, and the existing motor specifications. Our Korean engineering team confirms SK 12 vs SK 13 identification, returns the verified cross-reference and ships in 2-4 weeks.<\/p>\n

Submit Nord Cross-Reference Request \u2192<\/a><\/p>\n<\/div>\n

Redakt\u00f8r: Cxm<\/p>","protected":false},"excerpt":{"rendered":"

\u25e7 NORD CROSS-REFERENCE Nord SK Series Worm Gearbox Replacement: SK 12 vs SK 13 Decoded Visual identification, structural differences, cross-reference equivalence tables, and the substitution mistakes that fail when replacing single-stage SK 12 with two-stage SK 13. Get a Nord Cross-Reference Quote \u2192 Nord Drivesystems’ SK 12 and SK 13 worm gear reducer series occupy […]<\/p>","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_et_pb_use_builder":"","_et_pb_old_content":"","_et_gb_content_width":"","footnotes":""},"categories":[1337],"tags":[],"class_list":["post-1594","post","type-post","status-publish","format-standard","hentry","category-worm-gear-reducer"],"_links":{"self":[{"href":"https:\/\/wormreducers.xyz\/da\/wp-json\/wp\/v2\/posts\/1594","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/wormreducers.xyz\/da\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/wormreducers.xyz\/da\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/wormreducers.xyz\/da\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/wormreducers.xyz\/da\/wp-json\/wp\/v2\/comments?post=1594"}],"version-history":[{"count":1,"href":"https:\/\/wormreducers.xyz\/da\/wp-json\/wp\/v2\/posts\/1594\/revisions"}],"predecessor-version":[{"id":1595,"href":"https:\/\/wormreducers.xyz\/da\/wp-json\/wp\/v2\/posts\/1594\/revisions\/1595"}],"wp:attachment":[{"href":"https:\/\/wormreducers.xyz\/da\/wp-json\/wp\/v2\/media?parent=1594"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/wormreducers.xyz\/da\/wp-json\/wp\/v2\/categories?post=1594"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/wormreducers.xyz\/da\/wp-json\/wp\/v2\/tags?post=1594"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}