Shaft Keys — validation & limitations

What this calculator checks and the method behind each result, the independent reference cases its engine is tested against, and what it does not check. Use it to decide how far you can rely on a result.

Open the Shaft Keys

What it calculates

Standard / method: DIN 6885

Key & keyway DIMENSIONS: DIN 6885:1968 Part 1 · Load capacity (hub surface pressure): after DIN 6892 (simplified) · Shear check: Roloff-Matek · Woodruff key table DIN 6888 · spline screening check (not ISO 4156)

Parallel key shear and hub bearing-pressure safety factors with an application factor Ka
Hub-groove surface pressure by the DIN 6892 method (shaft groove and key flanks not checked), with key sections auto-selected from the DIN 6885 Part 1 table
Minimum key length for each failure mode — the length at which the safety factor is exactly 1.00
Multi-key comparison for 1, 2 or 3 keys with the fit-tolerance factor k_s, credited up to two keys
Woodruff key screening check with automatic selection from the DIN 6888 designation table
Spline contact-pressure and root-shear screening check with a 25 % tooth-engagement derate
Key and hub material library (C45, 42CrMo4, cast iron, S235, S355) with a custom override

Standards this tool applies

DIN 6885 — Parallel key shear (Roloff-Matek practice) and hub-groove bearing safety factors after DIN 6892 (hub groove only), minimum key length, DIN 6885 auto-dimension lookup, plus Woodruff and spline screening checks (badged as estimates).

Validation evidence — independent reference cases (1)

Each case runs the tool's engine on a worked example whose values come from a published source or a hand derivation from the cited equations, and an automated regression test asserts the engine against those values within the stated tolerance. "Conservative" means the engine is known to sit on the safe side of the reference and the test asserts that side. Sources are cited; their text is not reproduced.

Key shear, hub bearing and minimum key length

Agrees

Source: Budynas & Nisbett, Shigley's Mechanical Engineering Design, 9th/10th ed., Ch. 7, Example 7-6 (key selection)

Inputs: d 1 7/16 in, 40 hp at 600 rpm, 3/8 in square key, Sy 65 kpsi, n 2.80; L 1.5 in selected

Quantity	Reference value	Tolerance
bearing safety factor at book crushing length	2.800	1e-6 relative
shear / bearing safety factor at L 1.5 in	3.6088 / 3.1272	1e-6 relative
minimum key length (bearing governs)	12.183 mm	1e-6 relative
book lengths shear / crush	1.16 in / 1.34 in	0.5 %

tests/golden/REF-keys-shear-bearing.golden.test.ts

Limitations

Not checked by this tool

Shaft-groove and key-flank surface pressure (DIN 6892) — Only the hub groove is checked; with a hub harder than the shaft check the shaft groove with the shaft material
Fatigue of the key joint under reversing or shock torque — Allowables are static; apply the application factor and check fatigue per DIN 6892
Shaft strength and fatigue at the keyway — The keyway is a notch (about 2-3); check the shaft with a keyway feature in /shaft
Hub wall strength over the keyway — Check the hub outer diameter and wall per DIN 6892 hub-geometry rules or by FEA
Axial retention of the hub — The key carries torque only; secure the hub axially (shoulder, ring, set screw)
Taper and gib-head keys — Parallel keys only (plus the spline and Woodruff panels)

Results are engineering calculations for qualified users — see the disclaimer. Other tools: all validation pages · standards reference · symbols glossary.