Patent ID: 7010917

Claim:
In a turbocharger comprising a turbine wheel mounted to one end of a shaft for rotation within a turbine housing, and a compressor wheel mounted to the other end of the shaft for rotation within a compressor housing, the compressor wheel having an axial through bore extending between a first end of the wheel and a second end of the wheel, said second end being remote from said turbine, wherein the second end of the shaft extends through the bore and a short distance beyond the second end of the compressor wheel and a nut is threaded onto said second end of the shaft to apply a clamping force to the compressor wheel either directly or indirectly through an intermediate clamping member disposed around said shaft adjacent the second end of the compressor wheel, such that the second end of the compressor wheel has a radial surface contacting a radial surface of the nut or intermediate clamping member; a method comprising: treating at least one of said radial surfaces to increase its co-efficient of friction with respect to the other.