{"id":1950,"date":"2026-07-21T07:28:12","date_gmt":"2026-07-21T07:28:12","guid":{"rendered":"https:\/\/gearrack.top\/?p=1950"},"modified":"2026-07-21T07:28:12","modified_gmt":"2026-07-21T07:28:12","slug":"ring-gears-for-excavators","status":"publish","type":"post","link":"https:\/\/gearrack.top\/ko\/ring-gears-for-excavators\/","title":{"rendered":"Ring Gears for Excavators"},"content":{"rendered":"
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GEAR APPLICATION GUIDE \u00b7 RING GEAR \u00b7 R03<\/span><\/p>\n

Ring Gears for Excavators:
\nSwing Ring Gears, Final Drive Ring Gears and Replacement Specification<\/span><\/h1>\n

Excavator ring gears perform two of the most mechanically severe functions in any construction or mining machine \u2014 the swing ring gear enables the 360\u00b0 rotation of the excavator\u2019s upper structure around its undercarriage under the combined weight of the boom, arm, bucket, and counterweight assembly at potentially high angular deceleration, while the final drive ring gear transmits full track drive torque to the sprocket through each of the two planetary final drive gearboxes. Understanding the material, dimensional, and wear characteristics specific to each ring gear position is essential for both machine OEMs selecting specifications for new excavator designs and for maintenance engineers procuring replacement ring gears for existing fleet machines.<\/p>\n

42CrMo4 \u00b7 18CrNiMo7-6 \u00b7 50Mn \u00b7 Case Nitrided<\/span>
\nM8\u2013M20 \u00b7 Swing + Final Drive \u00b7 5T\u201370T Class<\/span>
\nKomatsu \u00b7 CAT \u00b7 Hitachi \u00b7 Doosan \u00b7 Volvo<\/span><\/div>\n<\/div>\n<\/div>\n
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SWING RING OD<\/p>\n

0.8 \u2013 3.5 m<\/p>\n

Excavator swing ring gear OD range. Mini excavator (1\u20133T): 0.8\u20131.2 m. Compact (5\u201310T): 1.0\u20131.6 m. Medium (15\u201330T): 1.4\u20132.2 m. Large (50\u201370T): 2.0\u20133.0 m. Mining shovel (100T+): 2.5\u20133.5 m. All swing ring gears use internal tooth form \u2014 the swing drive pinion gears on the upper structure mesh with internal teeth on the ring fixed to the undercarriage<\/p>\n<\/div>\n

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SWING RING MODULE<\/p>\n

M8 \u2013 M16<\/p>\n

Excavator swing ring gear module range. Mini: M8\u2013M10. Compact (5\u201310T): M10\u2013M12. Medium (15\u201330T): M12\u2013M14. Large (50\u201370T): M14\u2013M16. Material: 50Mn (Chinese standard) or 42CrMo4 QT + case nitrided for medium\/large excavator swing rings, through-hardened for mini excavators<\/p>\n<\/div>\n

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FINAL DRIVE RING<\/p>\n

M5 \u2013 M10<\/p>\n

Final drive internal ring gear module \u2014 smaller than swing ring because the planetary final drive operates at higher speed and lower torque per tooth. 18CrNiMo7-6 case carburized HRC 58\u201362 mandatory for final drive ring gears in all but the lightest mini excavator applications<\/p>\n<\/div>\n

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SWING TOOTH FORM<\/p>\n

Internal Spur<\/p>\n

Excavator swing ring gears use internal straight-tooth spur form \u2014 not helical. The zero helix angle eliminates axial thrust that would be undesirable in the large-diameter swing ring bearing. The internal spur tooth also allows easy visual inspection of the tooth surface condition during field maintenance inspection<\/p>\n<\/div>\n<\/div>\n

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Excavator Ring Gear Engineering \u2014 Swing Rings vs Final Drive Rings<\/h2>\n

The excavator contains two distinct and very different ring gear applications that share only their basic ring gear geometry \u2014 an annular ring with internal or external teeth. The swing ring gear (the large-diameter ring that allows the excavator superstructure to rotate relative to the undercarriage) and the final drive ring gear (the small ring inside each track final drive gearbox) differ in module (M8\u2013M16 vs M5\u2013M10), material (manganese steel or nitrided alloy steel vs carburized alloy steel), tooth form (internal spur vs internal helical on many designs), load type (combined radial and moment bearing loads vs pure planetary tangential tooth load), and failure mode (surface fretting and edge contact from ring gear tilt vs contact fatigue from planet gear load cycling).<\/p>\n

Korea Ever-Power’s ring gears for excavators<\/a> are manufactured in two distinct product lines matching these two applications: 50Mn or 42CrMo4 QT + case nitrided for swing ring gears (covering the 5T through 80T excavator size range), and 18CrNiMo7-6 case carburized for final drive ring gears (covering mini through large excavator final drive gearboxes). The swing ring gears are manufactured as complete slewing ring assemblies (ring gear + bearing raceway + ball or roller bearing elements + sealing ring) for the OEM market, and as ring-gear-only replacements for the aftermarket service market where the existing slewing ring bearing is still serviceable but the gear teeth are worn. The final drive ring gears are supplied as matching internal ring gear sets for planetary final drive replacement, paired with the planet gears, sun gear, and planet carrier as complete stage kits compatible with the specific excavator model\u2019s gearbox. For planetary final drive complete drive unit specification, see the planetary gearbox<\/a> design resource for excavator final drive stage arrangement and torque calculation.<\/p>\n

The swing ring gear wears through a fundamentally different mechanism than a standard ring gear in a gearbox. The excavator\u2019s upper structure rotates the swing ring gear relative to the swing drive pinions through a limited angular range in the majority of work cycles \u2014 digging typically involves repeated left-right swings of 60\u00b0\u2013120\u00b0 to move material from the dig face to a truck or stockpile. Each swing cycle reverses the swing ring gear direction, introducing a cyclic load reversal at the mesh contact point. Over time, the tooth surfaces in the frequently-used angular sector (the 60\u00b0\u2013120\u00b0 sector engaged during the dig-and-swing cycle) accumulate far more contact fatigue cycles than the remaining circumference, resulting in localised pitting and spalling in the active sector while the remainder of the ring is relatively unworn. This characteristic partial-circumference wear pattern is the defining diagnostic sign of swing ring gear fatigue \u2014 and it directly informs the replacement decision, because the amount of remaining usable tooth surface is the key life-extension variable.<\/p>\n

\"planetary
Korea Ever-Power 18CrNiMo7-6 case carburized internal ring gear for excavator final drive planetary gearbox \u2014 M6, 84 internal teeth, OD 310 mm, bore dimension and OD ground to H5 for housing press-fit. Case carburized to effective case depth 0.9\u20131.3 mm, HRC 59\u201362 tooth surface, shot peened tooth roots. Hobbed internal teeth to DIN 7 quality class. Used in 20T class excavator final drive second stage \u2014 paired with 20CrMnTi carburized planet gears and sun gear to form the complete second-stage planetary set. B10 life 12,000 hours at rated operating cycle per ISO 6336-6 with service factor 2.0. 100% magnetic particle inspection on all internal tooth surfaces after carburizing and before assembly. Dimensional inspection report supplied. Replacement supply for Komatsu PC200-series, Caterpillar 320-series, Hitachi ZX200-series and Doosan DX225-series final drives.<\/figcaption><\/figure>\n<\/section>\n
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Swing Ring Gear Specification, Wear Assessment and Replacement<\/h2>\n

The swing ring gear is one of the most expensive single components in an excavator \u2014 a replacement swing ring gear for a 30T excavator costs \u20ac5,000\u2013\u20ac15,000 depending on the machine make and model, compared to \u20ac200\u2013\u20ac800 for a typical final drive planet gear set. This cost makes the swing ring gear replacement decision an important economic and engineering choice that should be based on measured wear criteria rather than on elapsed hours alone. The OEM-published wear limit for swing ring gears is typically 15\u201320% reduction in tooth height (measured from the original tooth height at the pitch circle) before replacement is mandatory \u2014 at this wear level, the tooth strength has been reduced to the point where the contact fatigue safety factor S_H falls below 1.0 under the maximum swing acceleration torque, and tooth fracture under peak dynamic load becomes a credible risk.<\/p>\n

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Swing Ring Gear Wear Assessment Procedure<\/h3>\n

Excavator swing ring gear wear should be measured at each major service interval (every 4,000\u20136,000 hours) using a gear tooth vernier caliper or a purpose-made tooth caliper gauge. Measure at minimum 12 positions equally spaced around the full ring circumference, including at least 4 measurements in the actively-worn sector (the 60\u00b0\u2013120\u00b0 sector engaged during the machine\u2019s typical dig-and-swing cycle, identified by the visible surface contrast between worn grey and unworn golden-coloured tooth flanks). Compare each measurement to the original tooth height specification (typically OEM-published in the machine service manual, or calculable from the module: full tooth height = 2.25 \u00d7 module for standard addendum and dedendum).<\/p>\n

Record the measurements and the angular position of the minimum tooth height \u2014 if the minimum is below 85% of original (15% wear), replacement is recommended. If minimum is between 85% and 90% of original, begin planning procurement of the replacement ring and schedule installation at the next major service window. If minimum is above 90%, continue operation and re-measure at the next service.<\/p>\n<\/div>\n

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Swing Ring Gear Life Extension \u2014 Rotation Method<\/h3>\n

The partial-circumference wear pattern of excavator swing rings creates an opportunity for life extension not available with uniformly-worn gears \u2014 if the ring is rotatable relative to its mounting bolts, the worn sector can be rotated away from the active position and an unworn sector positioned in the active mesh zone. This ring rotation extends the effective life of the ring by the ratio of the ring circumference to the worn sector circumference \u2014 for a ring with 90\u00b0 worn sector, rotating by 90\u00b0 brings a fully fresh tooth sector into service, potentially doubling the ring\u2019s total service life before replacement.<\/p>\n

Requirements for ring rotation to be effective: (1) The bolted mounting holes in the ring must allow rotation \u2014 most OEM swing ring designs have equally-spaced bolt holes (every 10\u00b0\u201315\u00b0) that allow rotation in 10\u00b0\u201315\u00b0 increments. (2) The ring must be removed, rotated, and reinstalled \u2014 a 2\u20134 hour maintenance job with overhead lifting equipment. (3) The remaining unworn tooth surface must be sufficiently intact to justify the maintenance cost \u2014 this should be confirmed by tooth height measurement before committing to the rotation. Korea Ever-Power provides swing ring gear rotation guidance documents for the most common excavator models on request.<\/p>\n<\/div>\n<\/div>\n

\"alloy
Korea Ever-Power 42CrMo4 QT + case nitrided internal ring gear for excavator swing slewing ring application \u2014 M12, 120 internal teeth, OD 1,520 mm, wall thickness 35 mm, internal tooth profile cut and then gas nitrided (HV 650\u2013720 at depth 0.25\u20130.40 mm). The gas nitriding process is applied after the ring gear has been through-hardened and precision machined \u2014 it provides a hard, fretting-resistant tooth surface without the dimensional distortion that would occur with case carburizing at this large diameter. Mounting holes: 48 equally-spaced M20 bolt holes on a 1,460 mm bolt circle for the bolted connection to the slewing ring housing assembly. Blank manufactured from 42CrMo4 forged ring blank (not plate-cut), UT tested after forging. 100% MT inspection of all internal tooth surfaces after nitriding. Used in 20\u201330T class excavator swing ring replacement programmes for Komatsu, Hitachi, CAT, Doosan, and Sany excavator brands.<\/figcaption><\/figure>\n<\/section>\n
\"Korea
Korea Ever-Power excavator ring gear manufacturing facility \u2014 large-diameter swing ring gear hobbing and tooth profile inspection. Excavator swing ring gears present a challenging manufacturing problem at the intersection of large diameter (0.8\u20133.5 m) and high precision (the gear tooth must maintain consistent pitch accuracy around the full 360\u00b0 circumference to prevent speed variation in the swing drive that would be felt by the operator as jerky swing motion). Korea Ever-Power uses large-diameter vertical hobbing machines with table diameter capacity up to 4,000 mm for excavator swing ring production, with 100% pitch measurement at 24 equally-spaced positions around the ring circumference on a large-ring CMM after hobbing. Swing rings failing to meet the DIN 8 pitch tolerance at any position are rejected and re-hobbed, not accepted with local deviation \u2014 a single tooth spacing error above tolerance creates a detectable speed pulse in the swing drive that operators experience as a \u201cknock\u201d at a fixed angular position during swing, one of the most common field complaints leading to premature swing ring replacement.<\/figcaption><\/figure>\n
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Frequently Asked Questions \u2014 Ring Gears for Excavators<\/h2>\n
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Q 01<\/span><\/p>\n

Our 25T excavator swing drive is making a grinding noise during rotation. Is this the swing ring gear or the slewing ring bearing? How do we diagnose and is immediate repair needed?<\/p>\n<\/div>\n

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Distinguishing swing ring gear noise from slewing ring bearing noise is critical for correct repair planning: (1) Bearing noise characteristics:<\/strong> slewing ring bearing defects (ball or roller damage, raceway spalling) typically produce an intermittent clunking or crunching noise that varies with the angular position of the ring \u2014 if you rotate the ring slowly by hand (with the swing brake released) and the noise occurs at specific, repeatable positions, bearing element damage is likely. Bearing noise is also often accompanied by increased swing free-play (the upper structure can rock slightly in the horizontal plane when the swing brake is applied \u2014 this lateral rocking indicates bearing race wear). (2) Ring gear noise characteristics:<\/strong> swing ring gear tooth damage produces a rhythmic clicking or grinding that is proportional to swing speed (faster swing = faster clicking) and occurs throughout rotation rather than at specific positions. Gear tooth damage is also often accompanied by metal particles in the swing gear grease (if the swing ring is grease-lubricated). (3) Immediate repair assessment:<\/strong> a grinding noise that is new (not present at the last service check) indicates active material removal from either the gear or bearing \u2014 the machine should be operated with reduced swing acceleration until inspection can be performed. If the noise is accompanied by vibration visible to the operator, the machine should be taken out of service immediately. Swing ring gear damage that progresses to tooth fracture can cause the upper structure to seize in rotation during a heavy swing \u2014 a potentially dangerous condition when the boom is fully extended with a loaded bucket. Korea Ever-Power recommends a qualified excavator mechanic inspect the swing ring gear grease port (accessible without ring removal on most machines) by sampling the grease for metal particle content as the first diagnostic step.<\/p>\n<\/div>\n<\/div>\n

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Q 02<\/span><\/p>\n

What is the lead time and documentation for a swing ring gear and final drive ring gear replacement set for a Komatsu PC300 excavator?<\/p>\n<\/div>\n

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Korea Ever-Power replacement ring gear supply for Komatsu PC300-7\/PC300-8: Swing ring gear (internal, M12, approx. 1,380 mm OD, 42CrMo4 nitrided):<\/strong> lead time 35\u201350 days from order confirmation. The PC300 swing ring is manufactured from a forged 42CrMo4 ring blank, through-hardened, precision machined, and gas nitrided \u2014 the total process chain including NDT inspection and dimensional verification is the primary lead time driver. The PC300 swing ring is one of Korea Ever-Power\u2019s most stocked sizes \u2014 if an emergency shipment is needed, contact Korea Ever-Power to check current inventory of ring blanks at different process stages. Final drive ring gear (internal, M6, 18CrNiMo7-6 carburized, for stage 1 and stage 2):<\/strong> lead time 20\u201330 days from order confirmation, including carburizing, quench, grind, and 100% MT inspection. These are available as individual ring gears or as complete stage kits including planet gears, sun gear, and planet carrier. Documentation:<\/strong> 42CrMo4 forging certificate, heat treatment record (QT + nitriding cycle), MT inspection certificate, dimensional inspection report, and ISO 9001:2015 quality system certificate are supplied with the swing ring. 18CrNiMo7-6 material certificate, carburizing cycle record, case depth and surface hardness measurement, MT certificate, dimensional report supplied with final drive ring gears. All documentation is formatted for inclusion in the machine\u2019s maintenance record and, if required by the owner, for submittal to a third-party inspection agency (Bureau Veritas, SGS, T\u00dcV) for the machine\u2019s statutory inspection record.<\/p>\n<\/div>\n<\/div>\n

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Q 03<\/span><\/p>\n

Our excavator fleet includes 12 machines of the same model. Can Korea Ever-Power provide a framework supply agreement for ring gears at a committed price and lead time?<\/p>\n<\/div>\n

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Yes \u2014 Korea Ever-Power operates framework supply agreements for excavator fleet operators, mining companies, and equipment rental fleets with multiple machines of the same or similar models requiring recurring ring gear replacement. A framework supply agreement (FSA) specifies: (1) Part numbers and specifications:<\/strong> the swing ring gear and final drive ring gear part numbers for the agreed machine models, with the Korea Ever-Power equivalent specification (material, module, tooth count, heat treatment) confirmed by first-article inspection against the original OEM parts. (2) Price commitment:<\/strong> fixed pricing for a 12-month or 24-month period, protecting the customer from steel and energy cost fluctuation within the agreement period. (3) Lead time commitment:<\/strong> Korea Ever-Power pre-orders and holds ring blank inventory for FSA customers, reducing lead time from the standard 35\u201350 days (swing ring) to 20\u201330 days by eliminating the raw material procurement step. For the final drive ring gears, Korea Ever-Power may hold finished goods stock for the most common sizes under the FSA, enabling dispatch within 5\u201310 days from order. (4) Order flexibility:<\/strong> FSA orders can be placed in individual units (one ring gear per machine service event) without minimum order requirements, since the production schedule is pre-agreed in the framework. Contact Korea Ever-Power\u2019s key accounts team with the excavator model list, current annual ring gear consumption per machine, and preferred delivery lead time to receive a framework supply agreement proposal.<\/p>\n<\/div>\n<\/div>\n<\/div>\n<\/section>\n

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Explore Korea Ever-Power Gear Categories<\/h2>\n

Seven precision gear product lines for excavator, construction, mining and heavy equipment applications worldwide.<\/p>\n<\/div>\n

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\"spur<\/p>\n
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Spur Gears<\/a><\/p>\n

M8\u2013M20 \u00b7 excavator \u00b7 swing drive pinion<\/p>\n<\/div>\n<\/div>\n

\"helical<\/p>\n
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Helical Gears<\/a><\/p>\n

Heavy machinery \u00b7 gearbox \u00b7 mill drive<\/p>\n<\/div>\n<\/div>\n

\"bevel<\/p>\n
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\ubca0\ubca8 \uae30\uc5b4<\/a><\/p>\n

Right-angle \u00b7 pump \u00b7 auxiliary drives<\/p>\n<\/div>\n<\/div>\n

\"worm<\/p>\n
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Worm Gears<\/a><\/p>\n

Self-locking \u00b7 actuator \u00b7 slow drive<\/p>\n<\/div>\n<\/div>\n

\"ring<\/p>\n
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Ring Gears<\/a><\/p>\n

Swing ring \u00b7 final drive \u00b7 M8\u2013M16<\/p>\n<\/div>\n<\/div>\n

\"planetary<\/p>\n
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Planetary Gears<\/a><\/p>\n

Final drive planet \u00b7 swing stage \u00b7 kit<\/p>\n<\/div>\n<\/div>\n

\"plastic<\/p>\n
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Plastic Gears<\/a><\/p>\n

Sensor \u00b7 instrument \u00b7 light auxiliary<\/p>\n<\/div>\n<\/div>\n<\/div>\n<\/section>\n

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GET A QUOTATION \u00b7 KOREA EVER-POWER<\/p>\n

Need Ring Gears for Excavators?<\/h2>\n

Korea Ever-Power manufactures 42CrMo4 nitrided swing ring gears (OD 0.8\u20133.5 m, M8\u2013M16) and 18CrNiMo7-6 carburized final drive ring gears (M5\u2013M10) for all excavator brands \u2014 Komatsu, Caterpillar, Hitachi, Doosan, Volvo, Sany, Liebherr, and Hyundai. Complete final drive stage kits including planet gears, sun gear, and carrier. Framework supply agreements for fleet operators. MT inspection certificate included. ISO 9001:2015 certified.<\/p>\n

Request a Quotation \u2192<\/a><\/p>\n<\/div>\n

\ud3b8\uc9d1\uc790: Cxm<\/em><\/p>\n<\/div>\n<\/div>","protected":false},"excerpt":{"rendered":"

GEAR APPLICATION GUIDE \u00b7 RING GEAR \u00b7 R03 Ring Gears for Excavators: Swing Ring Gears, Final Drive Ring Gears and Replacement Specification Excavator ring gears perform two of the most mechanically severe functions in any construction or mining machine \u2014 the swing ring gear enables the 360\u00b0 rotation of the excavator\u2019s upper structure around its […]<\/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":[4566],"tags":[],"class_list":["post-1950","post","type-post","status-publish","format-standard","hentry","category-application-of-gears"],"_links":{"self":[{"href":"https:\/\/gearrack.top\/ko\/wp-json\/wp\/v2\/posts\/1950","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/gearrack.top\/ko\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/gearrack.top\/ko\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/gearrack.top\/ko\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/gearrack.top\/ko\/wp-json\/wp\/v2\/comments?post=1950"}],"version-history":[{"count":1,"href":"https:\/\/gearrack.top\/ko\/wp-json\/wp\/v2\/posts\/1950\/revisions"}],"predecessor-version":[{"id":1953,"href":"https:\/\/gearrack.top\/ko\/wp-json\/wp\/v2\/posts\/1950\/revisions\/1953"}],"wp:attachment":[{"href":"https:\/\/gearrack.top\/ko\/wp-json\/wp\/v2\/media?parent=1950"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/gearrack.top\/ko\/wp-json\/wp\/v2\/categories?post=1950"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/gearrack.top\/ko\/wp-json\/wp\/v2\/tags?post=1950"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}