Parallel key · nominal static screening
Parallel-key Nominal Stress Worksheet
Calculate nominal force, key shear and hub-side bearing pressure from documented geometry. DIN 6885-1:2021-11 defines dimensions and tolerances—not a universal allowable stress or automatic design approval.
Derived engineering equations—not DIN formulas
| Antal | Equation | Units / assumption |
|---|---|---|
| Tangential force | F = T/(d/2) = 2T/d | T in N·mm and d in mm gives F in N. |
| Nominal key shear | τ = F/(bℓeff) | Uniform shear over width × effective loaded length; N/mm² = MPa. |
| Nominal hub-side pressure | p = F/(cℓeff) | Uniform bearing over actual loaded contact height × effective length. |
| Utnyttjande | u = 100 × demand / entered allowable | Arithmetic comparison only; validity follows the entered design basis. |
| Length from allowable | ℓτ=F/(bτtillåta), ℓp=F/(cptillåta) | Does not select a standardized total length or key form. |
Dimensional check: N·mm/mm = N; N/(mm·mm) = N/mm² = MPa. Inch-pound inputs are converted internally using NIST factors: 1 ft·lbf = 1.355818 J, 1 in = 25.4 mm and 1 psi = 0.006894757 MPa.
Current DIN family and historical ISO reference
DIN 6885-1:2021-11 is the current corrected 17-page edition for deep-pattern parallel keys, dimensions, tolerances and mass; it replaces DIN 6885-1:2021-06. The family also has DIN 6885-2:2021-06 for deep-pattern machine-tool applications and DIN 6885-3:2021-06 for low pattern. A bare “DIN 6885” label is therefore incomplete. ISO/R 773:1969 was withdrawn on 1998-11-03 and is not a current ISO design authority.
SKF-published DIN 6885/1 reference geometry
The optional helper uses the public SKF Couplings catalog, Table 1. Its intervals are ovan the lower diameter and up to and including the upper diameter. It publishes width b, total key height h and hub keyseat dimension d+t₂. This worksheet uses the listed t₂ as the nominal screening contact height c; the actual drawing and fit must be checked. The catalog is a manufacturer reference, not a substitute for the licensed corrected DIN edition.
| Shaft d, mm (lower exclusive; upper inclusive) | b×h, mm | SKF hub t₂, mm | Shaft d, mm | b×h, mm | t₂, mm |
|---|---|---|---|---|---|
| >6–8 | 2×2 | 1.0 | >95–110 | 28×16 | 6.4 |
| >8–10 | 3×3 | 1.4 | >110–130 | 32×18 | 7.4 |
| >10–12 | 4×4 | 1.8 | >130–150 | 36×20 | 8.4 |
| >12–17 | 5×5 | 2.3 | >150–170 | 40×22 | 9.4 |
| >17–22 | 6×6 | 2.8 | >170–200 | 45×25 | 10.4 |
| >22–30 | 8×7 | 3.3 | >200–230 | 50×28 | 11.4 |
| >30–38 | 10×8 | 3.3 | >230–260 | 56×32 | 12.4 |
| >38–44 | 12×8 | 3.3 | >260–290 | 63×32 | 12.4 |
| >44–50 | 14×9 | 3.8 | >290–330 | 70×36 | 14.4 |
| >50–58 | 16×10 | 4.3 | >330–380 | 80×40 | 15.4 |
| >58–65 | 18×11 | 4.4 | >380–440 | 90×45 | 17.4 |
| >65–75 | 20×12 | 4.9 | >440–550 | 100×50 | 19.5 |
| >75–85 | 22×14 | 5.4 | Outside >6–550 mm: use manual verified geometry. | ||
| >85–95 | 25×14 | 5.4 | Exact forms, lengths, tolerances and acceptance: NEEDS_LICENSED_SOURCE. | ||
Why former rules were removed
The previous calculator used overall length as loaded length, assumed c=h/2, silently clamped every shaft above 200 mm to a 45×25 key, and showed green/red acceptance from arbitrary default allowables. Its inch-pound screen still labelled allowable inputs MPa, so entering psi produced a 145.038× utilization error. Unsupported universal claims for 1–1.5d length, Kt=1.5–2.5 and two keys each carrying 75% were also removed. Effective length, concentration, load sharing and allowable values are design-specific.
