Gear Coupling Size Chart — FGC, HGC, HRC & Tyre Sizes (2026)
One-stop gear coupling size chart for India — FGC 1–7, HGC, HRC 070–230, tyre F40–F140 and jaw L-series sizes, with torque, bore and misalignment ranges. Request full spec sheets from SMI.
This is a one-stop size reference for the gear couplings and flexible couplings most commonly specified in India. Use the size designations below to identify your coupling, then request the full dimensional spec sheet (bore, OD, length and exact torque per size) from SMI.
Size codes follow common industry conventions; exact per-size dimensions vary by manufacturer — always confirm against your drawing or existing coupling before ordering.
Flexible / Full Gear Coupling (FGC series)
SMI's full gear couplings run from FGC 1 (smallest) to FGC 7 (largest).
| Parameter | Range (FGC 1–7) |
|---|---|
| Size designations | FGC 1, 2, 3, 4, 5, 6, 7 |
| Torque range | 500 – 500,000 Nm (size dependent) |
| Bore sizes | 20 – 400 mm |
| Maximum speed | up to 5,000 RPM |
| Misalignment | Angular up to 1.5°, Parallel up to 3 mm |
| Temperature | −30 °C to +120 °C |
Half Gear Coupling (HGC series)
SMI's half gear couplings (one flexible gear hub + one rigid flange) are designated HGC 1 to HGC 6, sized to match the FGC torque steps.
HRC Coupling sizes
Standard taper-bush HRC couplings: HRC 070, 090, 110, 130, 150, 180, 230 — defined by bore range and torque.
Tyre Coupling sizes (F-series)
Tyre couplings: F40, F50, F60, F70, F80, F90, F100, F110, F120, F140, in pilot bore (A) or taper bush (TC).
Jaw / Star Coupling sizes (L-series)
Jaw (star) couplings: L-050, L-070, L-075, L-090, L-095, L-099, L-100, L-110, L-150, L-190, L-225, with elastomer spider.
How to use this chart
- Identify the family (gear, tyre, HRC, jaw) by your application and misalignment needs.
- Match required torque and shaft bore to the size step.
- For exact per-size dimensions and torque, request the spec sheet — or send your shaft size / a photo of the existing coupling.
Identifying a coupling when the markings are gone
Most enquiries that start "I need a replacement, I do not know the size" can be answered from measurements alone. Take these and we can identify the family and size without you stripping the drive twice.
| Coupling family | Measure these |
|---|---|
| Gear coupling (FGC / HGC) | Sleeve outside diameter, overall length, flange bolt circle and bolt count, both bores with keyways, hub tooth outside diameter if the sleeve is off |
| Tyre coupling (F-series) | Rubber element outside diameter and width, flange outside diameter, bolt circle, number of clamping bolts |
| HRC coupling | Hub outside diameter, overall assembled length, element outside diameter, taper bush number if visible |
| Jaw / star coupling (L-series) | Hub outside diameter, hub length, number of jaws, spider outside diameter |
Always measure the bore and keyway yourself rather than trusting an old drawing. Shafts get reworked, keyways get widened by a worn key, and a "50 mm" shaft that has been running loose may measure 49.6 mm. We machine to what is actually there.
What a size code does and does not tell you
Every series on this page is a size designation, not a specification. Two couplings marked the same size from different makers can differ in outside diameter, length, bolt circle and exact torque rating. What the code reliably tells you is the approximate torque class and bore range. What it does not tell you is whether the part will physically drop into your machine.
That is why the practical sequence is always: identify the family, narrow to the size step by torque and bore, then confirm the actual dimensions against your existing part or drawing before manufacture. On a replacement job we would rather see one photograph and four measurements than a size code alone.
Bore and keyway: the details that hold up orders
- Give the measured shaft diameter, not the nominal one, and say whether the shaft is worn.
- Give keyway width and depth, and say whether it is a single or double keyway. Parallel keys to IS 2048 are standard on most Indian equipment; if yours is a different standard or a non-standard key, say so.
- State the fit you want — interference, transition or clearance with a grub screw. Different machines want different answers and "standard" is not one.
- Tapered shafts need the taper ratio and the shaft end dimensions. Send a sketch.
- Say if the coupling will be fitted with heat. An interference fit intended to be shrunk on is machined differently from one meant to be pressed.
Getting from a size to a purchase order
The size chart narrows the field. These four items close the order:
- Service-factored torque. Calculate T = 9,550 × kW ÷ RPM at the coupling, then multiply by the duty factor for the driven machine. Size on that number, not on motor kW.
- Both bores and keyways, measured.
- Distance between shaft ends, plus any axial float the machine needs.
- Duty and environment — continuous or start-stop, reversing, ambient temperature, dust, oil exposure.
Our torque calculator does the first step, and the selection guide covers choosing between families.
Cross-family quick reference
| Family | Series | Reach for it when |
|---|---|---|
| Full gear coupling | FGC 1 – 7 | Highest torque, significant misalignment, heavy industry |
| Half gear coupling | HGC 1 – 6 | One flexible end is enough — floating shaft and similar arrangements |
| Grid coupling | By torque and bore | Shock loads, reversals, compressors and crushers |
| Tyre coupling | F40 – F140 | Large misalignment, shock, no lubrication wanted |
| HRC coupling | HRC 070 – 230 | General-purpose pumps, fans and light drives |
| Jaw / star coupling | L-050 – L-225 | Small to medium general drives, vibration damping |
| Chain coupling | By torque and bore | High torque, low speed, dirty conditions |
Detailed comparisons for the flexible families are in the coupling selection guide, and for grid couplings specifically in the grid coupling guide.
What to send us to get a spec sheet or a quote
- The size marking if it is legible, plus a photograph of the coupling in place.
- The measurements for your family from the identification table above.
- Both shaft diameters and keyway sizes, measured.
- Motor kW, RPM and the driven machine.
- Distance between shaft ends.
- Quantity and delivery location.
More questions on this
How do I identify a coupling with no visible markings?
Measure the family-specific dimensions — for a gear coupling that is sleeve outside diameter, overall length, flange bolt circle and bolt count, plus both bores and keyways. Send those with a photograph of the coupling in place and we can identify the size.
Does the same size code mean the same dimensions from every manufacturer?
No. A size code reliably indicates a torque class and bore range, but outside diameter, length, bolt circle and exact torque rating vary between makers. Always confirm actual dimensions against your existing part or drawing before manufacture.
Should I give you the nominal shaft size or the measured one?
The measured one, always. Shafts get reworked and worn, and keyways widen under a loose key. We machine to what is actually on your machine, so a measured diameter and keyway prevent a coupling that will not fit or will not grip.
Can you supply a coupling for a tapered or non-standard shaft?
Yes. Send the taper ratio and shaft end dimensions, or a sketch with measurements, along with the fit you need and whether the coupling will be heated on.
Need help sizing? See our selection guide or contact SMI's engineers for a recommendation and quote.
Super Mech Industries — Odhav, Ahmedabad, Gujarat 382415, India. Phone: +91 63510 70577. Email: smigvs@gmail.com. ISO 9001:2015 certified.