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Feather key connections

Feather key connections are machine elements which combine a shaft with a hub and are used for interlocking torque transfer via a driver, the actual feather key. The DIN 6885 Parts 1-3 series of standards deals with the geometry of feather keys. Both standard geometry and freely-defined feather key connections can be considered in the FVA-Workbench.

The load capacity of feather key connections is calculated according to DIN 6892 (2012). The occurring and permissible surface pressures on the root, feather key, and hub are compared. The shaft strength can also be verified according to DIN 743 or the FKM guideline.

Geometry of feather key connections

The DIN 6885 series of standards specifies the dimensions of feather key connections, among other things:

  • DIN 6885-1:2021-11 - Drive type fastenings without taper action, parallel keys, keyways - Deep pattern - Part 1: Dimensions, tolerances, mass

  • DIN 6885-2:2021-06 - Drive type fastenings without taper action, parallel keys, keyways - Deep pattern for machine tools - Part 2: Dimensions, tolerances, mass

  • DIN 6885-3:2021-06 - Drive type fastenings without taper action, parallel keys, keyways - Low pattern - Part 3: Dimensions, tolerances, mass

In the FVA-Workbench, the user can choose to use standard geometry according to DIN 6885 or specify a freely-defined feather key geometry.

When standard geometry is selected, the following parameters are determined based on the shaft diameter:

  • Feather key height and width,

  • Depth of the shaft and hub groove.

The following can also be automatically determined:

  • The chamfer or rounding of the feather key, and

  • The rounding of the groove base.

The specified feather key length is also checked.

Feather key strength verification according to DIN 6892

"DIN 6892:2012-08 Drive type fastenings without taper action - Parallel keys - Calculation and design" describes the strength verification of feather keys in 3 levels of detail:

  • Method A: Comprehensive experimental or computational strength verification. A general procedure is not currently available for this calculation method.

  • Method B: More detailed analysis of the occurring and permissible flank pressures on the shaft, feather key, and hub. Requires additional shaft strength verification according to the nominal stress concept.

  • Method C: Approximate determination of the flank pressures and estimation of the shaft stress

In the FVA-Workbench, the strength verification is calculated according to Method B, and the results according to Method C are also output.

Required inputs

The geometry of the hub to be considered must be specified in addition to the Geometry of feather key connections. It can be defined according to DIN 6892 as a hollow cylinder or as an offset hub consisting of two hollow cylinders. The shaft diameter will be determined from the shaft contour.

Any existing frictional torque can be determined and considered by specifying the fit between the shaft and hub along with other relevant parameters (roughness depth, coefficient of adhesion).

Information on the load (e.g., application factor, number of load peaks, any load reversals) and the materials to be used for the shaft, feather key, and hub is also required.

Torsional moment to be considered

If a single component calculation is performed for the feather key connection, the nominal torque, maximum torsional moment, and any reverse torsional moment must be specified.

The nominal torque transmitted through the feather key connection is automatically determined as part of the FVA-Workbench system calculation. By specifying the impact factor as well as the factor for reverse operation, the user can then determine the torsional moment to be considered as well as the reverse torsional moment.

Effective surface pressure

All influencing factors for determining the effective surface pressure described in DIN 6892 can be considered in the FVA-Workbench (load-bearing length and depth of the shaft and hub keyway, application factor, load-bearing factor, load distribution factor, friction factor). In particular, the load distribution factor K_λ is determined using the more precise method from the FVA REMOP program for exact calculation of shaft-hub feather key connections, and not just approximated based on the diagrams from section

Permissible surface pressure

The effective surface pressures are compared with the permissible surface pressures. The yield point and tensile strength of the materials, the influence of load direction changes, the influence of load peaks, the support factor, and the hardness influence factor are all considered.