Skip to main content
DraftFit
← All calculators

Parallel Key Calculator

Calculator mode
Unit system
Need help choosing a key?
Key Selection Assistant

What do you need?

Start from shaft diameter and transmitted torque. DraftFit selects the implemented DIN 6885-1 nominal section and sizes a preliminary key length.

1. Shaft, Torque & Strength Parameters

Strength assumptionsPreliminary

The 90 / 60 MPa preset is only the DraftFit default screening assumption. For design, enter allowables established for the real materials and applicable design method.

Primary result

10 × 8 × 50 mm

Nominal section selected from Ø35 mm. Calculated minimum nominal length: 58.1 mm; next preferred DraftFit length: 63 mm.

REVIEW
Required length58.1 mmREVIEW
Shear60 %OK
Contact120 %REVIEW
Controlling modeContact pressureREVIEW
A passing key check does not automatically validate the shaft or hub. The keyway reduces section and introduces stress concentration; reversing, shock, fatigue or highly loaded drives require additional checks.
DIN 6885-1:2021-11 — Ø35 mm10 × 8 × 50 mm
NOT OK

Parallel Key Geometry & Preliminary Verification

Key section b × h
10 × 8 mm
Shaft keyway depth t₁
5 mm
Hub keyway depth t₂
3.3 mm
Radial top clearance
0.30 mm

Preliminary Mechanical Verification

Tangential force Fₜ
14.29 kN
Effective bearing length
40.0 mm
Governing criterion
Contact pressure
Contact pressureNOT OK
CALC108.2 MPa
ALLOW90.0 MPa
Utilization: 120 %
Key shearOK
CALC35.7 MPa
ALLOW60.0 MPa
Utilization: 60 %

Key Length Sizing

Minimum effective length — pressure
48.1 mm
Minimum effective length — shear
23.8 mm
Governing minimum length
58.1 mm
Recommended nominal length
63 mm
Selected key length is shorter than the calculated minimum requirement.

2D SHAFT–KEY–HUB CROSS-SECTION

Ø35Key 10×8t₁ = 5t₂ = 3.3

Engineering Basis

Nominal key and keyway geometry follows the implemented DIN 6885-1:2021-11 deep-pattern series. The load-capacity check below is a simplified static screening calculation and is not a complete DIN 6892:2025-10 calculation.

DIN 6885-1Used here for the implemented nominal key and keyway dimensional series.
DIN 6892DraftFit does NOT represent the simplified shear/contact screening here as a complete DIN 6892 calculation.

Engineering Notes

• DIN 6885-1:2021-11 dimensional selection does not by itself verify the load capacity of the key connection.

• The stress calculation shown here is a simplified static engineering check and is not a complete DIN 6892:2025-10 calculation.

• Allowable pressure and shear stress must be selected from the actual key, shaft and hub materials and from the applicable design method.

• For reversing, shock, fatigue or highly loaded drives, additional factors and shaft/hub fatigue checks are required.

Engineering report

Your browser print dialog will open. Choose “Save as PDF”.

Formulas & methodology

  • Tangential force F = 2T / d.
  • Effective length Le is the load-carrying length used by the selected key-end treatment/model.
  • Average key shear stress τ = F / (b × Le).
  • Average bearing pressure is calculated from tangential force divided by the implemented projected bearing area.
  • Utilization = calculated stress / selected allowable stress.

Engineering basis & standards

  • Key cross-sections and keyway dimensions use the implemented DIN 6885-1 geometry ranges.
  • Strength checks are preliminary average-stress checks; detailed keyed-joint design may require DIN 6892 or another project-specific method.

Assumptions

  • Torque is steady or represented by a suitable design value and is transmitted through one conventional parallel key.
  • Load distribution is approximated as uniform over the effective length.
  • Selected allowable bearing and shear stresses already include appropriate material, duty and safety considerations.

Warnings / limits

  • Check shaft and hub stresses at the keyways, fatigue and stress concentration separately for cyclic/high-load applications.
  • Confirm the actual key length, end form, fit and hub geometry against the applicable drawing/standard.
Report calculation issue →

Related engineering reading

Key shear vs bearing pressure →35 mm shaft key size →DIN 6885 reference →