AGMA 9002 Flexible Coupling Calculator — Design Torque, Service Factor & Bore Tolerances
AGMA 9002 — Bores and Keyways for Flexible Couplings (Inch Series)
AGMA 9002 is the American Gear Manufacturers Association standard for bores and keyways of flexible shaft couplings (inch series). It establishes the dimensional tolerances for coupling bores, keyway widths and depths, and shaft fits that ensure interchangeability and proper torque transmission through the hub-to-shaft interface. Used alongside the AGMA 9000 series covering balance and service factors, AGMA 9002-B04 is the North American reference for specifying and verifying flexible coupling bores in industrial drivetrain applications.
The MechanixCalc shaft couplings calculator applies the AGMA 9002 / AGMA 9000 framework to compute the design torque (nominal torque multiplied by the service factor), the resulting torque safety factor against the catalog coupling capacity, and misalignment checks for radial, angular and axial offset. The tool covers jaw (spider), disc, Oldham, gear and rigid coupling types. Several sub-panels — including misalignment reaction forces, critical speed estimation and the coupling suitability ranking — are engineering estimates with in-app disclaimers; the design-torque and service-factor core follows AGMA 9002 / AGMA 9000 practice.
Calculators that implement AGMA 9002
What AGMA 9002 covers
- Bore and keyway dimensional tolerances for flexible coupling hubs — diameter fits, keyway widths and depths to AGMA 9002-B04 (inch series)
- Service factor K_s selection for driven-machine characteristics, load type and shock severity — light uniform (fans, centrifugal pumps) through heavy-shock (crushers, reciprocating compressors) per AGMA 9000 Table 1
- Design torque calculation: T_d = T_nom × K_s, with the coupling catalog torque capacity required to exceed T_d by the specified safety margin
- Torque safety factor SF = T_rated / T_d against catalog coupling capacity; minimum SF ≥ 1.5 for standard industrial duty
- Misalignment tolerance verification — radial (parallel offset), angular (shaft-to-shaft angle) and axial (end-float) — against per-coupling-type rated limits (referenced alongside ISO 14691 for disc couplings)
- Bore suitability check: shaft diameter must fall within the coupling's rated bore range, because oversized bores in a fixed coupling envelope reduce hub wall thickness and lower torsional capacity
Governing formulas
T_d = T_nom × K_swhere T_d = design torque (N·m or lbf·in); T_nom = nominal (rated) transmitted torque at the operating speed; K_s = service factor (dimensionless, typically 1.0–3.0 from AGMA 9000 Table 1 — accounts for load uniformity, shock level, reversals and starts per hour). The coupling catalog torque capacity must satisfy T_rated ≥ T_d × SF_min.
SF = T_rated / T_dwhere SF = torque safety factor (dimensionless); T_rated = coupling catalog torque capacity (N·m) at the selected bore; T_d = design torque (N·m). Minimum recommended SF = 1.5 for standard industrial duty; higher values apply for safety-critical or shock-loaded applications. A bore larger than nominal reduces T_rated because hub wall thinning lowers torsional stiffness.
Frequently asked questions
What is AGMA 9002 used for?
AGMA 9002-B04 specifies the bore and keyway dimensions — tolerances, fits and keyway proportions — for flexible shaft couplings in the inch series. It ensures that coupling hubs from different manufacturers are dimensionally interchangeable and that the hub-to-shaft interface transmits the design torque without fretting or slipping. Engineers also use the companion AGMA 9000 service factor tables (often cited together with AGMA 9002) to size the coupling for the driven-machine shock category and duty cycle.
How is the service factor determined under AGMA 9002 / AGMA 9000?
The service factor K_s is selected from the AGMA 9000 Table 1 based on the type of prime mover (electric motor, internal-combustion engine), the driven-machine load category (uniform, moderate shock, heavy shock), and the number of starts per hour. Typical values range from 1.0–1.5 for uniform loads (fans, centrifugal pumps) up to 2.0–3.0 for heavy-shock applications (crushers, reciprocating compressors, rolling mills). The design torque T_d = T_nom × K_s must be less than the coupling's catalog capacity divided by the required safety factor.
Does AGMA 9002 cover misalignment limits?
AGMA 9002-B04 itself focuses on bore and keyway tolerances, not on operational misalignment limits. Permissible misalignment (radial offset, angular deviation and axial displacement) is set by the coupling manufacturer and, for disc couplings, by ISO 14691. The MechanixCalc coupling calculator checks all three misalignment types against per-coupling-type rated limits from the coupling database and flags any exceedance with a warning.
What is the difference between AGMA 9002 and AGMA 9000?
AGMA 9000 ('Flexible Couplings — Potential Unbalance Classification') covers balance grades and service factor selection for flexible couplings. AGMA 9002 ('Bores and Keyways for Flexible Couplings — Inch Series') covers the dimensional requirements for coupling bores and keyways. The two standards are companion documents: AGMA 9000 tells you how much torque to design for and how the coupling must be balanced; AGMA 9002 tells you how to machine the bore and keyway to fit the shaft.
Is the AGMA 9002 coupling calculator free?
You can use it during a free 30-minute preview with no sign-up required, and a free 14-day account trial (no credit card) unlocks every calculator on MechanixCalc. The branded PDF engineering report with the full calculation trail and saved calculations are part of a paid plan.
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