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Comparison · Gear accuracy

ISO 1328 vs. DIN 3962 vs. AGMA vs. JIS: how gear accuracy classes map

Every RFQ arrives in a different tolerance language. A German drawing says DIN 8, an American one says AGMA Q10, a Japanese subsidiary writes JIS N7 — and they describe gears of roughly the same accuracy. This guide lines the systems up side by side, explains why no crosswalk is exact, and tells you which class to ask for.

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Comparison · Published 2026-09-12 · Wolfer Transmission

Four standards, two directions of counting

ISO 1328-1:2013 is the current international standard for cylindrical gear accuracy, with classes from 1 (finest) to 11 (coarsest). DIN 3962 / 3963 is the German system, quality grades 1 (finest) to 12 (coarsest), still the most common language on European OEM drawings; the 1995 edition of ISO 1328 grew out of DIN 3962, which is why the numbers line up so closely. JIS B 1702-1:1998 adopted the ISO 1328-1 classes outright (written with an N prefix, e.g. N6) and is what Japanese customers and their Chinese subsidiaries use; the pre-1998 JIS B 1702 (grades 0–8) used a different set of limits and cannot be read number-for-number.

AGMA is the one system that counts the other way. AGMA 2000-A88 uses Q-numbers from Q3 (coarsest) to Q15 (finest) — a higher number is a finer gear. Its replacement, AGMA 2015-1, switched to A-classes (A2–A11) where a lower number is finer, the same direction as ISO. When a US drawing lands, check first whether it says Q or A, or "tighter" and "looser" will be read backwards.

Why the crosswalk is only approximate

All four systems control the same elements — single pitch deviation fp, total cumulative pitch deviation Fp, total profile deviation Fα, total helix deviation Fβ and runout Fr — but the tolerance formulas and the module / diameter bands are not identical. One AGMA Q-number often straddles two ISO classes, and a DIN grade can be slightly looser than the same-numbered ISO class at small modules and slightly tighter at large ones. A crosswalk is therefore a communication tool, not a substitute for the tolerance values on the drawing.

Wolfer cuts and inspects to ISO 1328 by default: gears are measured in one setup on the PREC60 (Klingelnberg-type) gear measuring center for pitch, profile, helix and runout. When the drawing names DIN, AGMA or JIS, we cut to that standard and issue the inspection report in that standard's elements and units.

Gear accuracy class crosswalk (approximate, for communication — the drawing tolerances govern)
ISO 1328-1DIN 3962AGMA 2000-A88AGMA 2015-1JIS B 1702-1 (1998)Typical use / Wolfer process
Class 44Q13 / Q14A4N4Metrology and aerospace grade; grinding + profile modification + extra inspection
Class 55Q12 / Q13A5N5Servo reducers, machine-tool spindles, low noise; Wolfer ground standard
Class 66Q10 / Q11A6N6General industry and automation; Wolfer hobbed standard
Class 77Q9 / Q10A7N7General machinery, low-to-medium speed; hobbed / milled
Class 88Q8 / Q9A8N8Low speed, conveying, agricultural; milled

A row means "comparable accuracy level", not equal tolerance values. The pre-1998 JIS B 1702 (grades 0–8) does not map onto this table and must be converted from the tolerance values.

Which class should you ask for?

Classes 8 and 7: low-speed, conveying, agricultural and general reduction drives — hobbed or milled, lowest cost. Class 6: the mainstream class for general industry and automation, and Wolfer's default for hobbed gears; no grinding after heat treatment. Class 5: servo reducers, machine-tool spindles, noise-sensitive drives and any gear with a flank hardness above about 50 HRC — requires gear grinding after heat treatment, is Wolfer's default for ground gears, and adds 5–7 days to the lead time compared with class 6. Class 4 and finer: aerospace- and metrology-grade transmissions that need profile modification and additional inspection on top of grinding; quoted case by case.

One option that is often overlooked: accuracy can be specified per element. A positioning axis is usually most sensitive to cumulative pitch deviation Fp and helix deviation Fβ, which can be held to class 5 while profile Fα stays at class 6. That costs far less than raising the whole gear one class.

How to write it on the drawing

State the standard and its edition, then the class — for example "ISO 1328-1:2013, class 6 (fp, Fp, Fα, Fβ)". Tooth-thickness allowance and backlash belong to a separate system (DIN 3967, or the tooth-thickness tolerances in ISO 1328) and must be called out on their own: Wolfer's milled spur gears are made to DIN 3967 8d25 by default and the ground 40Cr series to JIS grade 2. Add module (or DP), number of teeth, pressure angle, helix angle and hand, face width, bore and keyway, material and heat-treatment hardness, and both the quotation and the inspection have something to be checked against.

FAQ

Common questions on this topic

Is ISO 1328 class 6 the same as DIN 3962 grade 6?

Comparable but not identical. The 1995 edition of ISO 1328 came directly from DIN 3962, so the class numbers line up; the 2013 revision changed some formulas and bands, so in individual module / diameter ranges the two can differ by about half a class. If the drawing says DIN grade 6, we machine and inspect to the DIN 3962 tolerance values.

What AGMA quality do Wolfer's ground gears correspond to?

Ground gears are ISO 1328 class 5 by default, roughly AGMA 2000 Q12–Q13 or AGMA 2015 A5; hobbed gears are class 6 by default, roughly Q10–Q11 / A6. Finer classes are evaluated per drawing.

Can the inspection report follow the standard on our drawing?

Yes. Wolfer inspects to ISO 1328 by default on the PREC60 gear measuring center — pitch, profile, helix and runout in one setup. When the drawing names DIN, AGMA or JIS, the report is issued in that standard's elements and units and ships with the parts.

Can I specify different classes for different elements?

Yes, and we recommend it. A positioning drive is sensitive to cumulative pitch and helix deviation, so those can be held to class 5 while profile stays at class 6. That is cheaper than raising the whole gear one class and matches how ISO 1328 evaluates each element separately.

Related reading

Precision Standards Gears Inspection

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