Run an immediately usable three-stage sizing screen, then move through evidence-backed boundaries, stage-count trade-offs, and RFQ actions in one page. Whether you searched 3 stage spur gear gearbox or the shorter 3 stage spur gearbox, this is the canonical page for that intent — it is intentionally tool-first and decision-focused.
Deterministic pre-RFQ checker with explicit boundary logic and uncertainty disclosure.
You already have motor speed, target output speed, and target torque and need a fast three-stage feasibility screen.
Your target ratio is too high for a comfortable two-stage solution and you need to confirm three-stage viability before RFQ.
Your project is in pre-RFQ stage and needs to eliminate clearly out-of-bound architectures first.
You need to place a final purchase order immediately and do not plan additional thermal/noise/life validation.
Your target ratio is far above 1500:1 or duty conditions are clearly outside this page boundary.
Your use case is safety-critical and requires regulation-grade validation, not screening-grade guidance.
This page screens a spur gear train. Spur and helical gears differ in force path, per-mesh efficiency, noise, and bearing cost — so for a three-stage stack the gear-type choice reshapes both the cost structure and the compliance risk.
| Attribute | Spur gear | Helical gear | Three-stage implication | Source |
|---|---|---|---|---|
| Tooth contact & force components | Straight teeth engage along the full face at once; force is purely radial (no axial thrust). | Angled teeth (15°–30° helix) engage gradually; force has radial + axial (thrust) components. | A three-stage spur train needs only radial bearings across all three shafts; a helical train needs thrust-capable bearings per stage, raising bearing count and cost. | S12 |
| Per-mesh efficiency | About 98–99% — near-pure rolling contact. | About 95–98% — sliding friction plus axial thrust loss. | The 96% “three-stage gearing” benchmark includes bearings, seals, and churning; pure spur mesh loss is lower. Do not read the stage benchmark as the mesh efficiency. | S12, S4 |
| Noise & engagement | Abrupt full-face engagement; noise rises sharply above ~1000–1500 rpm pitch line velocity (often 85–95+ dBA). | Gradual engagement; typically 10–20 dB quieter at comparable speed. | Three spur meshes stack sound power faster than three helical meshes; for high-speed three-stage spur trains, ISO 8579-1:2002 noise data becomes a hard gate, not optional. | S12, S13 |
| Load capacity per face width | Transverse contact ratio ~1.2–1.6; lower load sharing per face width. | Total contact ratio >2.0; roughly 50% higher load capacity per face width. | For the same output torque, a spur final stage needs a wider face or larger module than helical; this affects envelope and the strength check under ISO 6336 / AGMA 2101. | S12, S1 |
| Bearing & housing cost | Simple radial bearings; no thrust-bearing requirement from the gear mesh itself. | Thrust bearings (angular-contact / tapered roller) required; bearing spend typically 30–50% higher, plus stiffer housing. | Spur saves on bearings but the saved budget is often reallocated to noise treatment and a larger final-stage gear — it is a cost reallocation, not a free win. | S12 |
| Best operating speed band | Low-to-moderate pitch line velocity where noise is tolerable. | Higher speed and noise-sensitive continuous duty. | A three-stage spur gearbox is usually chosen for low-output-speed, high-torque duty where the output-stage pitch line velocity is low; at the high-speed input stage, noise may still dominate. | S12, S4 |
| Load nature | Duty window | SF range | Three-stage note | Source |
|---|---|---|---|---|
| Uniform load | 8–10 h/day | 1.00–1.25 | Lowest SF. Fits steady fans/blowers with uniform feed. The default 1.35 in this checker sits above this band, i.e. moderate-shock territory. | S14 |
| Moderate shock | 8–10 h/day | 1.25–1.50 | Default checker band (1.35). Fits belt conveyors with intermittent feed, mixers, and typical three-stage process duty. | S14 |
| Heavy shock | 8–10 h/day | 1.50–1.75 | Crushers, mills, apron/pan conveyors. Raises requested rated torque sharply; verify the final-stage gear strength explicitly. | S14 |
| Continuous duty adder | 24 h/day | +0.25 to the band above | Mandatory for three-stage units running around the clock; thermal capacity, not just mechanical rating, usually becomes the limiting factor. | S14 |
| Frequent starts/stops adder | ≥10 starts/stops per hour | +0.25 to +0.50 | Cyclic loading fatigues the three-stage stack faster; declare the actual start rate, not a nominal value. | S14 |
| Reversing duty adder | Bidirectional load | +0.50 (or specify reversing unit) | Reversing loads both flanks; assembled-stack backlash then directly affects positioning and tooth impact — capture backlash in RFQ terms. | S14 |
Bands apply to enclosed spur/helical industrial drives below ~7000 ft/min pitch line velocity; peak load must not exceed 200% of the unit rating. The checker default 1.35 sits in the moderate-shock band.
| Market | Trigger | Requirement | Sourcing impact | Source |
|---|---|---|---|---|
EU market placement (motor/drive package included) EU Commission page verified 2026-06-17 | Applies when in-scope electric motors or variable speed drives are part of the supplied system. | Regulation (EU) 2019/1781 applies from 2021-07-01; IE3 is required for many 0.75–1000 kW 3-phase motors, IE4 is mandatory for 75–200 kW categories from 2023-07, and in-scope VSDs must meet IE2. | A mechanically suitable gearbox quote can still fail procurement if bundled motor/drive efficiency classes are non-compliant. | S11 |
U.S. plant operation (occupational noise) OSHA page + ISO 8579-1:2002 verified 2026-06-17 | Applies when gearbox-motor assemblies can affect workplace noise exposure levels. | OSHA Table G-16 uses time-weighted limits (90 dBA/8 h, 95 dBA/4 h, 100 dBA/2 h), and the hearing-conservation action level is 85 dBA (8-hour TWA). Supplier sound data should be produced under ISO 8579-1:2002 (grade 2 engineering method preferred) at the real duty point so the dBA value is reproducible. | Noise data without a named measurement standard is not auditable; remediation costs can exceed small unit-price savings, especially for three-mesh spur trains. | S7, S13 |
| Subject | Known boundary | Decision implication | Source |
|---|---|---|---|
| ISO 6336 method validity envelope | Validated formula envelope includes pressure angle 15°–25°, helix angle ≤30°, and transverse contact ratio 1.0–2.5. | If your geometry sits outside this envelope, request supplier method extension or test evidence before freezing design. | S1 |
| ISO 281 bearing-life interpretation | Basic rating life is linked to 90% reliability (L10 concept), not a direct warranty life commitment. | Require reliability percentile, duty cycle, and lubrication assumptions in RFQ life claims; bearing count rises with stage count. | S10 |
| Catalog ratio versus architecture | A public family shows standard ratios up to i=289.74 but double gear units up to i=27,001. | Do not treat total ratio alone as a fair comparison proxy; capture stage count and architecture in quote templates. | S5 |
| Gear-unit noise measurement method | ISO 8579-1:2002 is the current acceptance code for airborne sound of gear units/gearmotors (1993 edition withdrawn). It defines grade-2 engineering and grade-3 survey methods plus standardized mounting/operating conditions. | A single dBA number without ISO 8579-1 method, measurement grade, load point, and speed is not reproducible — require the measurement method in the RFQ, not only the result. | S13 |
| Enclosed-drive service-factor classification | ANSI/AGMA 6013-B16 (consolidates 6010-F97) defines uniform/moderate/heavy shock bands (1.00–1.25 / 1.25–1.50 / 1.50–1.75 at 8–10 h/day) with adders for continuous, frequent-start, and reversing duty; peak load capped at 200% of unit rating. | Tie the service factor you input to a declared shock class and duty; an unsupported SF cannot be audited and may under- or over-size the three-stage stack. | S14 |
Three-stage reduction is selected when the target ratio, thermal limit, or pinion/shaft strength cannot be met by two stages. Public vendor families cover wide two-/three-stage windows (for example i up to 289.74 in one family), so three-stage is a deliberate efficiency-for-ratio trade, not a default.
Boundary: Whether three-stage is actually required depends on your exact ratio, power, and envelope; some mid-ratio needs are still better served by two stages.
Sources: S5, S4
A current industrial benchmark reports roughly 98% (1-stage), 97% (2-stage), and 96% (3-stage). Because losses compound across three meshes, the same duty maps to higher heat rejection and higher energy OPEX than fewer stages.
Boundary: These are directional benchmarks from one manufacturer context; model-level efficiency at your duty point must be confirmed in the RFQ.
Sources: S4
ISO 6336 and AGMA 2101 are rating frameworks for pitting/bending capacity and factor handling; they do not by themselves validate assembled three-stage drivetrain behavior, especially shaft deflection and housing stiffness across the longer stack.
Boundary: Thermal, NVH, lubrication, bearing life, and system integration still require supplier test data and acceptance criteria.
Sources: S1, S3
Total backlash in a three-stage spur train is the cumulative contribution of all three meshes, so supplier "precision" statements must be tied to flank tolerance class terminology and a defined measurement method for the whole stack, not one mesh.
Boundary: Cross-supplier comparisons are weak if class definitions, temperature state, load state, and whether backlash is quoted per stage or assembled are missing.
Sources: S2, S5
Current EIA references show U.S. industrial electricity at 8.95 cents/kWh (2026-02 monthly) versus 8.62 cents/kWh (2025 annual average). Because three-stage loss power is higher, this price spread scales into larger absolute annual cost than it would for a two-stage unit.
Boundary: Energy price is location- and contract-dependent; this checker is a screening estimate, not a financial guarantee.
Sources: S8, S9
EU market rules for motors and drives have dated thresholds: Regulation (EU) 2019/1781 applies from 2021-07-01, with IE4 mandatory for selected 75–200 kW motor categories from 2023-07 and IE2 requirements for in-scope drives.
Boundary: This compliance gate is region- and product-scope-dependent; apply only when your shipment includes in-scope motor/drive content for the EU market.
Sources: S11
OSHA Table G-16 pairs noise with allowed duration (90 dBA/8 h, 95 dBA/4 h, 100 dBA/2 h), and hearing-conservation actions start at 85 dBA (8-hour TWA). Three meshes raise the baseline sound-power budget, so duration-corrected noise data matters more, not less.
Boundary: This is a U.S. occupational benchmark and does not replace local jurisdiction rules or machine-specific noise certification.
Sources: S7
One public family lists standard R-series ratios up to 289.74 while double gear units can reach 27,001, so a high catalog ratio claim may involve four or more effective stages rather than three.
Boundary: Do not compare quote prices by total ratio alone; require stage count, architecture, and efficiency chain to be declared.
Sources: S5
Spur gear meshes run at about 98–99% per mesh because contact is near-pure rolling with no axial thrust — only radial loads. The widely cited ~96% “three-stage gearing” figure includes bearing, seal, and oil-churning losses across the whole stage, not just the three meshes. So a three-stage spur train is not “inherently lossy at the teeth”; the losses are distributed across mesh friction, bearings, seals, and lubricant churning, and each is a separate RFQ lever.
Boundary: Mesh-efficiency figures are directional and depend on pitch line velocity, surface finish, and lubrication; request a loss breakdown (mesh vs bearing vs churning) rather than one blended stage number.
Sources: S12, S4
Because spur gears produce only radial force, they need no thrust bearings (saving roughly 30–50% on bearing spend vs helical) and use a simpler housing. But spur teeth engage abruptly, so above roughly 1000–1500 rpm pitch line velocity the sound power climbs (often 85–95+ dBA), and with three meshes that climb compounds. The saved bearing budget is usually reallocated to noise treatment and a larger final-stage gear, so a three-stage spur unit is not automatically cheaper to own than a helical one.
Boundary: At low output speeds (the typical three-stage high-torque regime) the output stage stays quiet; the noise risk concentrates at the high-speed input stage — measure there first.
Sources: S12, S13
Per ANSI/AGMA 6013-B16 (which consolidated 6010-F97), service-factor bands are tied to load nature and duty: uniform 1.00–1.25, moderate shock 1.25–1.50, heavy shock 1.50–1.75 at 8–10 h/day, with documented adders for 24 h continuous (+0.25), frequent starts (+0.25–0.50) and reversing (+0.50). The standard also caps peak load at 200% of the unit rating. The checker default of 1.35 places a typical three-stage process drive in the moderate-shock band — confirm your real shock class before reusing it.
Boundary: These bands are for enclosed spur/helical industrial drives below ~7000 ft/min pitch line velocity; outside that scope, or for safety-critical duty, request a project-specific rating per ANSI/AGMA 2001-D04 / 2101-E25 instead.
Sources: S14, S3
1. Total ratio i = motor rpm / output rpm.
2. Stage split estimate uses ∛i (cube root) for quick three-stage distribution.
3. Output power uses P(kW)=T(Nm)×n(rpm)/9550.
4. Total efficiency estimate cubes the per-stage efficiency assumption (η_total = η_stage³).
5. Annual loss cost = loss power × duty × 365 × electricity price.
This method intentionally avoids fake precision: where public evidence is weak, outputs are labeled as screening-only and escalated to verification tasks.
| Question | Known from sources | What you still must verify |
|---|---|---|
| Strength calculation method | ISO 6336 / AGMA 2101 are core rating frameworks, with ISO 6336 formula validation published inside defined geometry envelopes. | If geometry is outside published validity ranges, request explicit method extension or empirical test closure. |
| Three-stage ratio and structure availability | Public product families show broad two-/three-stage windows; high catalog ratios can involve compound architecture. | Your target ratio, footprint, and gearbox envelope compatibility, plus declared stage count. |
| Efficiency | Public benchmark example: about 98/97/96% gearing by stage count (whole stage incl. bearings/seals/churn); spur per-mesh efficiency is ~98–99% (near-pure rolling, no axial thrust). EIA industrial price references currently range from 8.62 to 8.95 c/kWh by data window. | Supplier-specific loss breakdown (mesh vs bearing vs churning), test method, and load-point curve plus price-sensitivity check before final total cost ranking. |
| Gear type: spur vs helical | Spur: radial force only, ~98–99% per mesh, noisier above ~1000–1500 rpm, contact ratio ~1.2–1.6. Helical: radial + axial thrust, ~95–98% per mesh, 10–20 dB quieter, contact ratio >2.0. | Decide gear type against pitch line velocity and the site noise ceiling before comparing quotes; spur saves on bearings but reallocates budget to noise treatment and a larger final-stage gear. |
| Life and reliability | ISO 281 defines 90% reliability basic rating life basis. | Bearing selection details, lubricant contamination, duty transients — bearing and seal count rise with stage count. |
| Regional market compliance | EU motor/VSD rules apply by scope and date (2019/1781 in force from 2021-07-01; IE4 applies to selected 75–200 kW categories from 2023-07). | Verify bundled motor/drive compliance before commercial award, not after mechanical shortlist. |
| Topic | Status | Impact | Minimum action |
|---|---|---|---|
| Cross-brand three-stage spur efficiency distribution (same test method) | Partial: spur per-mesh efficiency documented (~98–99%); cross-brand stage-level distribution under one test method still pending | Spur mesh loss is now referenceable, but bearing/seal/churning loss varies by supplier. Cross-brand catalog stage-efficiency can still mislead when test conditions differ. | Require a loss breakdown (mesh vs bearing vs churning), test duty point, efficiency map points, oil temperature, load range, and measurement uncertainty in RFQ data. |
| Public failure/return-rate benchmarks by stage count in each industry | No reliable public dataset | Public averages are not sufficient to predict your project-level failure probability, and three-stage stacks add bearing and seal count. | Request supplier failure-mode history, 8D cases, in-warranty return definitions, and sample size details. |
| Public supplier lead-time samples by region and specification | Pending confirmation (insufficient public samples) | Procurement schedule risk is hard to quantify accurately from public data alone. | Bind latest acceptable delivery dates in RFQ terms and lock lead-time commitments separately for sample, pilot, and mass-production phases. |
| Option | Useful ratio window | Efficiency reference | Strongest use case | Main risk | Evidence status |
|---|---|---|---|---|---|
| Single-stage spur/helical | Low reduction, typically i up to about 6–8:1 for one mesh. | About 98% (stage benchmark example) | Simple, compact speed changes where one mesh is enough. | Cannot reach the ratios a three-stage page is screening for. | Public product-family evidence exists, same-method cross-brand datasets remain limited. |
| Two-stage spur/helical parallel-axis | Typical medium-to-high reduction demand; public family examples can reach i≈289.74 (series-specific). | About 97% (stage benchmark example) | Balanced target across efficiency, structural complexity, and cost when the ratio fits two stages. | May require three stages once ratio, thermal, or strength limits bind. | Public product-family evidence exists, same-method cross-brand datasets remain limited. |
| Three-stage spur/helical | Higher total reduction ratios, typically for low-speed high-torque output. | About 96% (stage benchmark example) | When two-stage paths cannot satisfy ratio and thermal limits simultaneously. | Additional stage increases efficiency, thermal, backlash, and bearing-count burden. | Public stage-level benchmarks exist, model-level confirmation is still required. |
| Worm-dominant architecture | High single-stage reduction potential (series dependent). | Public values vary significantly; model-tested data is required. | Space-constrained layouts with explicit self-locking behavior requirements. | Heat loss and lubrication window can become primary project risks. | Public evidence is fragmented and cross-brand comparability is weak. |
| Planetary hybrid path | Common in high-ratio and high power-density applications. | Depends on stage count and architecture; supplier curves are required. | When package size constraints and torque density have higher priority. | Higher procurement cost and tighter tolerance-control demand. | Product documentation is available, unified cross-brand test comparisons are still limited. |
| Common claim | Counterexample | Action |
|---|---|---|
| “Three stages always deliver more torque for the same price.” | Three stages trade efficiency and thermal headroom for ratio. Where two stages suffice, three stages add loss, heat, backlash, and bearing count without torque benefit. | Confirm the ratio genuinely exceeds the two-stage window before selecting three stages. |
| “One measured dBA number is enough for compliance.” | OSHA limits are tied to both level and duration; 95 dBA is limited to 4 hours and 100 dBA to 2 hours. | Request noise data by duty cycle and define acceptance at real operating duration, not only nameplate conditions. |
| “A fit result guarantees lowest operating cost.” | EIA industrial electricity references vary (8.62 c/kWh 2025 annual vs 8.95 c/kWh Feb 2026), changing annual loss cost even with identical loss power. | Use multi-price sensitivity in RFQ evaluation and lock the financial assumption date. |
| “A spur gearbox is just a cheaper helical gearbox.” | Spur gears save 30–50% on bearings (no axial thrust, radial bearings only) but run noisier above ~1000–1500 rpm and carry less load per face width (contact ratio ~1.2–1.6 vs >2.0). The bearing saving is usually reallocated to noise treatment and a larger final-stage gear. | Decide spur vs helical against pitch line velocity and noise ceiling first, then compare total cost — not against bearing cost alone. |
Boundary misuse risk
High/HighTreating screening output as final procurement approval without thermal, noise, and life validation.
Mitigation: Limit this page to pre-RFQ filtering and enforce a mandatory validation matrix before award.
Efficiency-compounding risk
High/MediumAssuming three-stage loss is "just one more percent" when losses compound across three meshes into higher heat rejection.
Mitigation: Run the loss-power and annual-loss estimate with your real duty, then size cooling and oil capacity accordingly.
Cost mismatch risk
High/MediumComparing only unit purchase price while ignoring the larger energy-loss cost of three stages.
Mitigation: Calculate loss-cost baseline with current electricity price and run annual sensitivity bands.
Scenario mismatch risk
Medium/MediumApplying light-duty parameters to high-shock duty can leave service factor below safe range.
Mitigation: Declare shock class, duty cycle, and service-factor source explicitly in RFQ terms.
Backlash accumulation risk
Medium/MediumQuoting single-mesh backlash hides the cumulative backlash of a three-stage stack, breaking positioning repeatability.
Mitigation: Require assembled-stack backlash with measurement method, temperature state, and load state.
Keep this page as the canonical three-stage screening entry, then move to RFQ actions and adjacent architecture pages for full feasibility closure.
Assumptions: Service factor 1.35, 3-stage efficiency 96%/stage, 16 h/day, industrial electricity price 8.95 c/kWh.
Process: Total ratio i=60, split across three stages at about 3.9:1 each.
Result: Falls in the three-stage sweet spot. Produces actionable screening inputs, but thermal balance and backlash tests are still required.
Assumptions: Attempting to cover an ultra-high reduction ratio with three stages at comparable power.
Process: The checker enters boundary state and recommends compound or mixed-architecture review.
Result: Prevents out-of-bound results from being misused as direct order decisions.
Assumptions: Target output ratio is moderate (for example i≈30) and duty is light.
Process: The checker flags conditional/not-fit and recommends a two-stage review to avoid paying an efficiency penalty you do not need.
Result: Redirects the decision to the lower-stage option before RFQ spend is wasted on the wrong architecture.
Assumptions: Nominal torque rating is identical, but test definitions and stage-count declaration are undisclosed.
Process: The risk layer flags the offers as non-comparable and outputs a minimum evidence request list.
Result: Shifts evaluation from quote-price debate to evidence completeness and controllable risk.
1. Continuous torque and efficiency curves with declared test method, at your duty point.
2. Thermal boundaries (oil temperature, housing temperature, duty definition) — critical for three-stage heat rejection.
3. Backlash/tolerance class for the assembled three-stage stack (not one mesh) with measurement condition.
4. Bearing-life evidence (ISO 281 basis, reliability %) and lubrication assumptions tied to duty cycle.
1. Declared stage count and architecture path (to catch compound units marketed as “three-stage”).
2. Separate lead time commitments for sample, pilot, and production lots.
3. Warranty and failure-mode reporting scope with data cut definition.
4. Change-control obligation for material, process, or tolerance updates.
Core conclusions are linked to traceable sources. If evidence is weak or unavailable, the page explicitly labels it as "pending confirmation/no reliable public dataset" instead of inventing certainty. Review cadence: every 6 months or earlier when standards or data are updated.
ISO 6336-1 validates the calculation basis inside specific geometry ranges (pressure angle 15°–25°, helix angle ≤30°, transverse contact ratio 1.0–2.5) and does not guarantee assembled drive-system behavior by itself.
https://www.iso.org/standard/63819.htmlDefines tolerance class structure and allowable flank deviation values for cylindrical involute gears.
https://www.iso.org/standard/45309.htmlLists ANSI/AGMA 2101-E25 (published 2025-07-31) and records ANSI/AGMA 2001-D04 as replaced by 2101-E25.
https://www.agma.org/wp-content/uploads/2026/03/MPMA_Publications_Catalog.pdfShows stage-dependent gearing efficiency benchmark: 98% (1-stage), 97% (2-stage), 96% (3-stage). Three stages carry the highest baseline efficiency cost of the three.
https://download.sew-eurodrive.com/download/html/33346739/en-EN/891277287548168610059.htmlLists R-series ratio i=3.21–289.74, reduced-backlash i=3.5–281, and double gear units up to i=27,001, confirming that high-ratio catalog claims can involve compound architecture beyond three stages.
https://www.sew-eurodrive.com.co/products/gear_units/standard_gear_units/helical_gear_units_r/helical_gear_units_r.htmlGives horsepower conversion used in sizing checks: 1 hp = 745.6999 W.
https://www.nist.gov/pml/special-publication-811/nist-guide-si-appendix-b-conversion-factors/nist-guide-si-appendix-b8Provides enforceable thresholds for screening: Table G-16 includes 90 dBA/8 h, 95 dBA/4 h, 100 dBA/2 h, and the hearing-conservation action level is 85 dBA (8-hour TWA).
https://www.osha.gov/laws-regs/regulations/standardnumber/1910/1910.95Reports U.S. industrial electricity price at 8.95 cents/kWh for February 2026 (release date 2026-04-23).
https://www.eia.gov/electricity/monthly/epm_table_grapher.php?t=epmt_5_6_aShows U.S. industrial average electricity price at 8.62 cents/kWh (2025 annual value) and 8.95 cents/kWh (February 2026 monthly value).
https://www.eia.gov/electricity/monthly/epm_table_grapher.php?t=table_5_03Defines basic rating life at 90% reliability (L10 concept) and scope boundaries; relevant for bearing-life evidence in three-stage stacks where bearing count is higher.
https://www.iso.org/standard/38102.htmlStates scope (0.12–1000 kW), entry into application on 2021-07-01, IE4 requirement for 75–200 kW motors from 2023-07, VSD IE2 requirement, and projected annual savings of 106 TWh by 2030.
https://energy-efficient-products.ec.europa.eu/product-list/electric-motors_enSpur gears transmit only radial force (no axial thrust) with near-pure rolling contact, giving per-mesh efficiency around 98–99%; helical gears add an axial force component and sliding friction, lowering per-mesh efficiency to about 95–98%. Spur transverse contact ratio is roughly 1.2–1.6 versus >2.0 for helical, so helical carries about 50% more load per face width but needs thrust bearings. Canonical basis: Shigley’s Mechanical Engineering Design.
https://gearsolutions.com/features/comparative-analysis-of-spur-and-helical-gearsCurrent standard (status 90.93) for determining the airborne sound emission of gear units and gearmotors. It defines the allowed measurement methods (engineering grade 2 and survey grade 3), operating and mounting conditions, so that declared sound power / sound pressure levels are reproducible. The 1993 edition is withdrawn and replaced by the 2002 edition.
https://www.iso.org/ics/17.140.20.htmlGoverns design, rating, lubrication, testing, and selection of enclosed spur/helical/herringbone/double-helical/spiral-bevel drives in single or multistage arrangements. Service-factor bands: uniform load 1.00–1.25, moderate shock 1.25–1.50, heavy shock 1.50–1.75 (8–10 h/day); add 0.25 for 24 h continuous, 0.25–0.50 for frequent starts/stops, 0.50 for reversing; peak load must not exceed 200% of the unit rating (mechanical capacity at unity service factor). Pitch-line-velocity scope: <7000 ft/min or ≤4500 rpm.
https://www.agma.org/standards/C1. Three-stage is the choice when two-stage hits a wall.
C2. Three stages cost the most efficiency of the standard stack.
C3. Strength calculations are necessary but insufficient.
C4. Backlash accumulates across three stages.
C5. Energy-price assumptions materially change total-cost ranking.
C6. Regulatory fit can invalidate a mechanically valid shortlist.
C7. Noise risk is time-weighted and worsens with mesh count.
C8. Catalog ratio headlines can hide architecture complexity.
C9. For SPUR gears the mesh efficiency is higher than the 96% stage benchmark implies.
C10. Spur trades bearing cost for noise cost — it is a reallocation, not a saving.
C11. Service factor is not a free multiplier — it is standardized and capped.
Keep this result as screening evidence, then launch RFQ validation with thermal, backlash, bearing-life, noise, and delivery commitments.
This page is an engineering screening aid, not legal/compliance advice and not a substitute for validation. For safety-critical or regulated deployments, escalate to certified design review and machine-level risk assessment.
