Why the Sequence Matters — Dependencies Between the Seven Questions
The seven questions in this guide are not independent — later questions depend on the answers to earlier ones. The correct dependency chain is: shaft geometry → power and ratio → service factor → module/size → environment and material → accuracy class → documentation. Skipping steps or working out of sequence produces specifications that are internally inconsistent — for example, specifying DIN Class 5 for a slow-running M12 gear (unnecessarily expensive) or DIN Class 7 for a 30 m/s pitch-line velocity gear (unachievable without grinding). Work through the questions in order for every new спирална предавка обществени поръчки.
Shaft
geometry
Power &
съотношение
Service
factor
Модул
& size
Environment
& material
Шум
& DIN
Documentation
Question 1 — What Is the Shaft Arrangement?
Parallel shafts → confirmed спирална предавка application → спирална предавка (proceed to Q2). Non-parallel, non-intersecting → crossed helical or worm gear. Intersecting at 90° → bevel gear. The vast majority of industrial drives use parallel shafts — the спирална предавка the default starting point for any drive specification exercise. If the shaft arrangement is genuinely fixed at 90° by machine layout, confirm whether a bevel gear (intersecting shafts) or a worm gear (non-intersecting) is the correct solution before proceeding with the спирална предавка selection process.
Question 2 — What Are the Power, Speed, and Required Gear Ratio?
The three fundamental drive parameters determine the transmitted force magnitude and the pitch-line velocity — the two quantities that govern all subsequent specification choices:
Step 2a: Transmitted torque T₁ = 9550 × P [kW] / n₁ [RPM] [N·m]
Step 2b: Gear ratio i = z₂/z₁ = n₁/n₂
Step 2c: Tangential force (estimated, before module is known):
F_t_est ≈ 2T₁ / d₁_estimate (use d₁ ≈ 60–120 mm as first estimate)
Step 2d: Pitch-line velocity v_est = π × d₁_est × n₁ / 60,000 [m/s]
The pitch-line velocity estimate from Step 2d immediately constrains the DIN accuracy class (Q6) — if v_est > 15 m/s, DIN Class 5 grinding will be required regardless of noise requirements. Record this early, as it affects cost before the module is known.
Question 3 — What Is the Application Service Factor (KA)?
The service factor KA amplifies the transmitted force through the entire specification — a higher KA requires a larger module, wider face width, or harder material. Determine KA from the AGMA 2101 power source and driven machine classifications (see the dedicated service factor guide, Art49):
| Application Category | Typical KA Range | Key Driver | Governing Specification Risk |
|---|---|---|---|
| VFD-driven centrifugal pump/fan (smooth) | 1.00–1.25 | VFD limits start torque; uniform load | Easy to underestimate if DOL motor used instead |
| Conveyor, compressor, machine tool | 1,25–1,50 | DOL motor start; moderate load variation | Verify motor start method before fixing KA |
| Mining, crane, heavy press | 1.75–2.50 | Shock loading; frequent heavy start | Both fatigue KA and static peak check required |
| Rubber mixer, crusher (impact) | 2.50–4.00 | Frozen charge; tramp iron impact | Static bending check at T_peak governs module |
Question 4 — What Module and Face Width Are Needed?
With T₁, KA, and the gear ratio i, the required module Mn can be estimated from the ISO 6336 contact stress formula simplified to a preliminary sizing equation:
Preliminary module estimate (contact stress governs, carburized 20CrMnTi material, S_H = 1.1):
Mn_est ≈ 1.5 × (T₁ × KA × (i+1) / (i × b_ratio × z₁² × σ_H_lim²))^(1/3)
where b_ratio = b/d₁ ≈ 0.8 (typical industrial)
z₁ = 20–24 (assumed pinion tooth count)
σ_H_lim = 1500–1600 MPa (carburized)
Simpler field formula (±30% accuracy):
Mn_est ≈ (T₁ × KA)^0.33 / 10 [mm, for T₁ in N·m]
Examples:
T₁ = 500 N·m, KA = 1.25 → Mn_est ≈ (625)^0.33 / 10 ≈ 8.5/10 ≈ 0.85 → try M1 or M1.5 (small drive)
T₁ = 5,000 N·m, KA = 1.5 → Mn_est ≈ (7500)^0.33 / 10 ≈ 19.6/10 ≈ 2.0 → try M2–M3
T₁ = 50,000 N·m, KA = 2.0 → Mn_est ≈ (100,000)^0.33 / 10 ≈ 46/10 ≈ 4.6 → try M5
Question 5 — What Is the Operating Environment and Required Material?
Material selection for a спирална предавка is driven by the operating environment as much as by load — the same module M5 gear may require 20CrMnTi carburized in a standard industrial application, SS316L in a food-processing or chemical environment, or 17CrNiMo6 with Charpy −40°C certification in a cold-climate marine or offshore installation
| Environment | Material Requirement | σ_H lim Range | Special Considerations |
|---|---|---|---|
| Standard industrial (enclosed, clean, ambient) | 20CrMnTi carburized (preferred) or 42CrMo QT | 490–1650 MPa depending on treatment | Material tier matched to required σ_H; ISO 6336 MQ grade standard |
| Food contact or pharmaceutical (wet, hygienic) | SS316L stainless steel, or FDA-grade POM/PEEK polymer | 200–450 MPa (SS316L); 20–90 MPa (polymer) | FDA 21 CFR compliance; NSF H1 lubricant; no EP additives near food |
| Marine or offshore (salt air, intermittent immersion) | 17CrNiMo6 carburized; Charpy −40°C certification for cold climates | 1600–1800 MPa | EN 10204 3.2 material certificate; class society survey (DNV, LR) |
| Chemical (acid, alkali, solvent exposure) | SS316L or Duplex SS (2205); hard coating on request | 180–420 MPa (SS316L) | Confirm chemical compatibility of coating or base material with process fluid |
| High temperature (>120°C continuous) | H13 tool steel or 17-4PH stainless for high-temp applications | 800–1200 MPa at 120°C | Oil viscosity selection critical: VG 220+ synthetic oil at high ambient temperature |
Question 6 — What Are the Noise, Vibration, and Precision Requirements?
The pitch-line velocity from Q2 and the noise/precision target together determine the DIN accuracy class for the спирална предавка:
DIN Class 7–8 (as-hobbed) is adequate. No tip relief required. This covers most slow industrial conveyors, mixers, and pump drives. The спирална предавка can be left in the as-hobbed condition after heat treatment — saving the grinding step.
DIN Class 5–6 (ground). Tip relief recommended. K_V at 15 m/s for Class 7 is 1.35–1.5 — marginal for the gear strength calculation. Most enclosed industrial gearboxes with carburized спираловидни зъбни колела fall in this category.
DIN Class 4–5 mandatory. Parabolic tip relief required. At v > 15 m/s, K_V for Class 7–8 exceeds acceptable limits. This covers EV reducers, compressor gearboxes, printing presses, and all high-precision servo спирална предавка приложения.
DIN Class 3–4 with isotropic superfinishing (Ra ≤ 0.05 µm). Tip relief and lead crowning both required. Applies to EV final stage (top NVH tier), security printing, aerospace instrument gears. Korea Ever-Power achieves DIN Class 3 with TE < 2 µm.
Question 7 — What Documentation and Certification Is Required?
Documentation requirements determine the inspection scope and supplier qualification level. Specifying more documentation than is genuinely needed adds cost and lead time; specifying too little creates risk at incoming inspection and installation. The correct documentation scope for each спирална предавка application category:
| Приложение | Required Documentation | Certificate Type |
|---|---|---|
| Standard industrial replacement | Gear analyser report (profile + lead + pitch); hardness survey; dimensional check | EN 10204 2.2 (test report by manufacturer) |
| Critical industrial or OEM supply | All above + EN 10204 3.1 material certificate + OES spectrometer + case depth traverse | EN 10204 3.1 (authorised inspector signature) |
| Marine / offshore / power generation | All above + class society 3.2 certificate (DNV, LR, BV, KR) with witness survey | EN 10204 3.2 (independent inspector; class society) |
| Automotive OEM (EV, passenger vehicle) | IATF 16949 supplier; PPAP Level 3; dimensional CMM report; TE curve from analyser; FMEA | PPAP (production part approval process) per AIAG manual |
| Food / pharmaceutical | FDA 21 CFR material compliance letter + EN 10204 3.1 + NSF H1 lubricant certificate | FDA material compliance; NSF H1 |
The Complete 7-Question Specification Summary
Korea Ever-Power’s engineering team reviews every спирална предавка order against the seven-question specification checklist before confirming the order — ensuring that shaft geometry, power, service factor, module, material, DIN class, and documentation are all consistent and complete before production begins
A correctly completed specification for a спирална предавка order to Korea Ever-Power answers all seven questions explicitly:
Q1 Shaft: Parallel shafts → helical gear confirmed
Q2 Drive: 75 kW, 1500 RPM input, i = 3:1 → T₁ = 477 N·m, v_est = 10 m/s
Q3 Service: Loaded conveyor, DOL start → KA = 1.50
Q4 Module: Mn_est = (716)^0.33/10 ≈ 0.89 → select M2 → confirm ISO 6336 at M5, z₁=24
Q5 Material: Standard industrial, no food/marine → 20CrMnTi carburized HRC 58–62
Q6 Accuracy: 10 m/s, noise < 75 dB(A) → DIN Class 5–6, tip relief C_α = 12 µm
Q7 Documents: Critical OEM pump drive → EN 10204 3.1 + gear analyser + hardness survey
Korea Ever-Power’s engineering review confirms the ISO 6336 strength calculation for both pitting (S_H = 2.8) and bending (S_F = 4.6), and issues the order confirmation with all seven parameters locked before production begins. As a direct производител на спирални зъбни колела, Korea Ever-Power requests the answers to all seven questions at the enquiry stage — not just module and material. Browse the complete продуктова гама от спирални зъбни колела for standard and custom specifications.
Често задавани въпроси
Underestimating the service factor KA for a спирална предавка — particularly treating a DOL motor drive as KA = 1.0 without checking the motor’s starting torque method. A direct-on-line (DOL) started induction motor applies 250–350% of rated torque at each startup. For a drive that starts 5 times per day under moderate load, this gives an effective AGMA “light shock” source classification — requiring KA ≥ 1.25. Using KA = 1.0 for this drive produces a спирална предавка that is undersized by approximately 20–30% for the actual loading history, leading to premature pitting or tooth root fatigue at 40–60% of the calculated design life. The fix — confirming the motor starting method and daily start count before fixing KA — takes 5 minutes and prevents a gear failure.
A standard catalogue спирална предавка (typically DIN Class 7–8, QT material, standard module and bore from stock) is acceptable when: Q1–Q6 answers produce a specification that falls within a standard catalogue size; the application is not safety-critical (failure would cause production loss, not injury or environmental damage); the pitch-line velocity is below 5 m/s; and the service factor is below 1.5. When any of these conditions is not met, a custom-specified спирална предавка — with ISO 6336 calculation, gear analyser verification, and EN 10204 3.1 certificate — is the correct choice. Korea Ever-Power offers standard stock gears for the first condition and custom production for all others.
With all seven questions answered at the time of enquiry, Korea Ever-Power’s standard lead times are: DIN Class 7–8 QT спирална предавка (as-hobbed, no grinding): 2–3 weeks. DIN Class 5–6 carburized and ground: 4–6 weeks. DIN Class 4–5 with tip relief, marine documentation: 6–8 weeks. PPAP automotive: 10–14 weeks (PPAP process in addition to production). These lead times assume complete specification — questions that require engineering clarification (ambiguous shaft arrangement, missing KA information, unspecified centre distance) each add 1–2 weeks. The seven-question спирална предавка framework is designed to eliminate these clarification cycles before production starts.
Yes — this is Korea Ever-Power’s standard pre-sales engineering service. Provide the application type (conveyor, mixer, pump, printing press, EV, etc.), rated power, input speed, and the driven machine (or its output speed/torque requirements). Korea Ever-Power’s engineering team completes the seven questions using the application-specific standards and field experience data, performs the ISO 6336 strength calculation for the selected module, and returns a complete specification recommendation — module, material, DIN class, tip relief, documentation scope, and indicative price — within 2–3 business days. This specification recommendation is non-binding and is provided free of charge before any order commitment.
Get Your Helical Gear Specification Reviewed
Send Korea Ever-Power your answers to the seven questions for your спирална предавка — or just the application type, power, and speed. Korea Ever-Power’s engineering team completes the specification, performs ISO 6336 calculations, and returns a module, material, DIN class, and documentation recommendation within 2–3 business days. Free of charge, no obligation to order.
7-question framework · ISO 6336 calculation · Module + DIN class + material recommendation · 2–3 business days · No obligation
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