In order to extract sharp edges from file c-wheel.stl by means of surfaceFeatureExtract utility a surfaceFeatureExtractDict file needs to be created first. This file is to be located in the system subdirectory. An example of the file content reads:

/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  2.2.2                                 |
|   \\  /    A nd           | Web:      www.OpenFOAM.org                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       dictionary;
    object      surfaceFeatureExtractDict;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

c-wheel.stl
{
    extractionMethod    extractFromSurface;

    extractFromSurfaceCoeffs
    {
        includedAngle   150;
    }

    writeObj                yes;
}

// ************************************************************************* //

To perform the extraction, use following:

 surfaceFeatureExtract

It extracts edge features and saves it to file c-wheel.eMesh located in the constant/triSurface subdirectory. Parameter includedAngle specifies the angle in degrees. Edges having lower angle between its faces are written down. Option writeObj set to yes means the output will also be written to constant/extendedFeatureEdgeMesh/
c-wheel_edgeMesh.obj file. Format .obj can be viewed in paraview:

 paraview