Standards & Specifications
IS 12405: the Indian standard for gear type flexible couplings
IS 12405:1988 is the Bureau of Indian Standards specification for gear type flexible couplings. Where AGMA 9002 dimensions only the bore, IS 12405 addresses the coupling itself — two designs, their ratings and dimensions, materials, sealing, lubrication and marking — and it leaves the service factor table to the manufacturer.
- Author
- Priyansh Thummar, Editor
- Dates
- Published · Last updated
- Reading time
- 3 minutes
1. What IS 12405 covers
IS 12405:1988, reaffirmed in 2006, is the Bureau of Indian Standards specification for gear type flexible couplings. Its scope is the general requirements of gear couplings used to connect two shaft ends for power transmission.
That is a different role from the one AGMA 9002 plays. AGMA 9002 dimensions the bore and keyway and stops there; IS 12405 addresses the coupling as a product, which puts it in the category of a whole-coupling standard rather than a component practice.
2. Type A and Type B
The standard defines two designs. Type A has both hubs flexible, with integral sealing by O-rings. Type B has a detachable sealing arrangement. Each type has its own table of ratings and dimensions by coupling number, and Type B carries an additional table for the spigot. Dimensions are in millimetres.
3. What it specifies
Beyond the tables, the clauses are short.
| Subject | What the standard requires |
|---|---|
| Ratings and dimensions | Tabulated by coupling number for Type A and Type B; the manufacturer provides the service factor table for selection |
| Hub and sleeve material | 45C8 steel to IS 1570 (Part 2), or cast steel for sleeves; heat treated to HB 240–280 |
| Teeth | Cut with module cutters; tooth characteristics, including crowning, agreed between supplier and user |
| Sealing | Integral with the sleeve, or an agreed alternative; O-rings to 120 °C, pressed felt or lip seals by agreement |
| Lubrication | Filling and drain plugs; calcium-base EP grease within 80 °C ambient, oil above; quantity per size stated by the manufacturer |
| Balancing | Generally not required (machined all over); by agreement for specific duty |
| Marking | Manufacturer's name or trade mark, type and coupling number, and the standard's designation |
| Packing | Wooden boxes |
4. What it leaves to the manufacturer
What the standard leaves open matters as much as what it fixes. It requires the manufacturer to provide the service factor table, so the factor that turns a motor rating into a selection torque comes from the supplier rather than from the standard. Crowning and other tooth characteristics are a matter of agreement, as are alternative seals and balancing.
The ratings it tabulates belong to its own coupling numbers. A manufacturer’s own size series may not follow them, so an offer should say which table and coupling number it corresponds to.
5. Against AGMA practice
The first difference is at the shaft. AGMA 9002 works in inch-series bores and keyways. Metric practice specifies bores with ISO 286 fits and parallel keys to metric standards such as IS 2048. That is a different tolerance grammar, not a stricter or looser version of the same one, and converting between the two by rounding a dimension is a common way a bore mismatch reaches site.
The second difference is scope. IS 12405 speaks to material, sealing, lubrication and marking, none of which AGMA 9002 addresses.
6. Putting it on an order
Where an Indian purchase specification names IS 12405, state the type and coupling number — or the duty it is to be selected for — and ask for the service factor table the selection used. State the bore fit and key standard: the standard’s dimension tables do not replace the shaft details of the actual machine.
Say whether you require the coupling to be manufactured to IS 12405 or only to be interchangeable with an existing installation — those are different requests. And put anything beyond the standard, such as a balance grade, a particular test or a documentation format, in the enquiry rather than in the inspection report.
Frequently asked
- What does IS 12405 cover?
- The general requirements for gear type flexible couplings used to connect two shaft ends for power transmission. It defines two designs — Type A, with both hubs flexible and integral O-ring sealing, and Type B, with a detachable sealing arrangement — tabulates ratings and dimensions for each, and specifies hub and sleeve material, sealing, lubrication provision, balancing, marking and packing.
- Does IS 12405 give service factors?
- No. It requires the manufacturer to provide the service factor table used to select a suitable coupling for each application. A purchase order that names IS 12405 but no duty has therefore left the most consequential selection input to the supplier.
- How does IS 12405 differ from AGMA 9002?
- AGMA 9002 dimensions the bore and keyway in inch series and stops there. IS 12405 addresses the coupling as a product, in millimetres, which puts it in the category of a whole-coupling standard rather than a component practice. A specification naming AGMA 9002 alone has specified the shaft interface and left the coupling itself unspecified.
- Is IS 3238 the Indian standard for gear couplings?
- We could find no Bureau of Indian Standards record of IS 3238. The BIS specification for gear type flexible couplings is IS 12405:1988. An earlier edition of this page used the IS 3238 designation; it has been corrected, and the old address redirects here.
References
- IS 12405:1988 (reaffirmed 2006), Specification for gear type flexible couplings. Bureau of Indian Standards.
- IS 1570 (Part 2), Schedules for wrought steels for general engineering purposes — Carbon steels, for the 45C8 hub and sleeve material.
- ISO 286-1:2010, Geometrical product specifications (GPS) — ISO code system for tolerances on linear sizes, for the metric fits referenced in section 5.
- IS 2048, Parallel keys and keyways. Bureau of Indian Standards.
- AGMA 9002-B04, Bores and Keyways for Flexible Couplings (Inch Series), for the inch-series practice compared in section 5.
- Correction, 15 September 2026: earlier editions of this article, at /standards/is-3238, named the Indian gear coupling standard IS 3238 and described its role without its text. We could find no Bureau of Indian Standards record of that designation. The article now describes IS 12405:1988, checked against the published text of the standard, and the old address redirects here.
- Editorial note: clause content is paraphrased, and the rating and dimension tables are deliberately not reproduced. Confirm the current status of the standard and any amendments with the Bureau of Indian Standards before citing it on an order.
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