ISO 606 Chain Drive — Roller Chain Selection & Sprocket Geometry Calculator
ISO 606 — Short-pitch transmission precision roller and bush chains, attachments and associated chain sprockets
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ISO 606 is the international standard for short-pitch precision roller and bush chains, their attachments, and the associated sprocket geometry. It defines the chain pitch series (from 04B at 6 mm pitch through 48B at 76.2 mm pitch), the minimum breaking load for each size and strand count, and the sprocket pitch-circle, tip and root diameter formulae. ANSI B29.1 is the North American counterpart: its A-series chains (ANSI No. 25–240) share many pitches with the B-series but have different roller and width dimensions, so the two are not interchangeable.
In practice, ISO 606 is the reference a designer reaches for when sizing a chain drive: the chain is selected by comparing the design load (nominal power × service factor) against the chain's minimum breaking load divided by a speed-dependent safety factor, and the sprocket geometry is then computed to the ISO 606 tooth-form formulae. MechanixCalc implements the complete selection, geometry, polygonal-effect and wear-life method online and generates a method-cited PDF engineering report suitable for design review handover.
Calculators that implement ISO 606
What ISO 606 covers
- Chain pitch series and dimensional parameters — pitch, roller diameter, inner width, plate thickness and minimum breaking load (Tables 1–3 of ISO 606)
- Sprocket geometry — pitch-circle diameter, tip (addendum) diameter and root diameter formulae for all tooth counts
- NOT in ISO 606: the lubrication-type classification. ANSI B29.1 defines THREE types — Type A (manual OR drip), Type B (oil bath or slinger disc) and Type C (oil stream / pressure spray) — selected from its horsepower rating tables by small-sprocket size and speed. Drive SELECTION guidance more broadly is ISO 10823. ISO 606 itself tabulates chain and sprocket dimensions and minimum breaking loads
- NOT ISO 606: the multiple-strand factors used to derate a multi-strand drive for load-sharing inequality. Those are ANSI/ACA values (K_s = 1.7 duplex, 2.5 triplex, 3.3 quad; Shigley §17-5 Table 17-22), and drive SELECTION guidance is ISO 10823 — ISO 606 itself tabulates chain and sprocket dimensions and breaking loads
- Service factor application and the speed-dependent safety factor used to select the minimum chain size for the design load
- Replacement criterion — the ANSI 1.5 % pitch-elongation limit that triggers chain renewal (referenced alongside ISO 606 in chain manufacturers' application guidance)
Governing formulas
d = p / sin(π / z) [mm]where d = pitch-circle diameter (mm); p = chain pitch (mm); z = sprocket tooth count. The tip (outer) diameter follows da = p · (0.6 + cot(π / z)), and the root diameter df = d − d_roller, where d_roller is the roller diameter from ISO 606 Table 1.
v = z₁ · p · n₁ / 60 000 [m/s] ; MBL_req = (P_d · 1000 / v) · SF / (strands · η_s · 1000) [kN per strand]where v = chain speed (m/s); z₁ = driver tooth count; n₁ = driver speed (rpm); P_d = design power = P · Ks (kW); SF = speed-dependent safety factor; strands = number of chain strands; η_s = per-strand efficiency, defined so that strands × η_s is the published ANSI/ACA multiple-strand factor K_s = 1.0 / 1.7 / 2.5 / 3.3 for simplex / duplex / triplex / quad (η_s = 1.000 / 0.850 / 0.833 / 0.825)
δv = (1 / cos(π / z₁) − 1) × 100 %where δv = peak-to-peak speed variation (%); z₁ = driver tooth count. At z₁ = 17 teeth δv ≈ 1.73 %; at z₁ = 19 teeth δv ≈ 1.38 %; at z₁ = 25 teeth δv ≈ 0.8 %. ISO 606 recommends ≥ 17 driver teeth, with an odd count to distribute roller-seat wear evenly around the sprocket.
Frequently asked questions
What is ISO 606 used for?
ISO 606 defines the geometry and minimum breaking loads of short-pitch precision roller chains and the associated sprocket tooth forms. Engineers use it to select the right chain size for a given power and speed (by checking the required breaking load against the chain's rated breaking load — the MechanixCalc calculator uses its own conservative values, below the published minimum), to compute sprocket pitch-circle and tip diameters, and to determine the required lubrication type. It is the standard cited in chain-drive calculations throughout Europe and internationally; ANSI B29.1 is the North American equivalent.
How do I select a roller chain to ISO 606?
Multiply the nominal transmitted power by the service factor Ks (1.0 for smooth load, up to 1.75 for heavy shock) to get the design power. Compute the chain speed v = z₁ · p · n₁ / 60 000 m/s, then the required minimum breaking load MBL_req = (P_d × 1000 / v) × SF / (strands × η_strand × 1000) kN, where SF is a speed-dependent safety factor. Select the smallest chain whose breaking load meets MBL_req (MechanixCalc uses conservative values below the published minimum tensile strength; confirm the rated value of the chain you buy). Each pitch has its own chain speed, so check every size at its own speed; above its critical speed the rating is capped for roller-bushing impact. The MechanixCalc chain calculator checks every size this way and selects the smallest that qualifies at a chain speed of 15 m/s or less.
What does the polygonal (chordal) effect mean and how do I reduce it?
Because a sprocket is a polygon, the chain speed rises and falls once per tooth pitch even at constant input speed. The variation is δv = (1/cos(π/z₁) − 1) × 100 %. At z₁ = 11 teeth δv ≈ 4.2 %, causing noticeable vibration and noise; at z₁ = 17 teeth it drops to ≈ 1.73 %, and at 25 teeth to ≈ 0.8 %. ISO 606 recommends at least 17 driver teeth. An odd tooth count on the driver sprocket distributes roller wear evenly because each roller contacts a different tooth on successive revolutions.
Which chain lubrication type applies, and where is it defined?
ISO 606 does not classify lubrication at all — it is a dimensions and breaking-load standard. The classification is ANSI B29.1's, and it defines THREE types, not four: Type A is manual OR drip lubrication (both together), Type B is oil bath or slinger-disc, and Type C is oil stream / pressure spray. The type is selected from the ANSI horsepower rating tables by small-sprocket size and speed, because both chain speed and transmitted power drive it. The MechanixCalc chain calculator offers drip, bath and forced, which map to Type A, Type B and Type C respectively. Providing the correct lubrication type is a prerequisite for achieving the tabulated power rating — it does not credit additional capacity, but failing to provide it shortens chain life significantly.
Is the ISO 606 chain calculator free?
You can run a full chain selection and geometry calculation during a free 30-minute preview session with no sign-up required. A free 14-day account trial gives access to every MechanixCalc tool — no credit card needed. The branded PDF engineering report with the full ISO 606 method and selected chain data, and saved calculations, are included in the free 14-day trial and in every paid plan.
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