Which statement about end play is correct?

• A. The fillet radius controls end play
• B. The main bearings limit end play
• C. Both statements are correct
• D. Neither statement is correct

Answer: (D)

End play is the small axial movement of the crankshaft in the engine, caused by the clearance on the crank’s thrust surfaces. What actually sets this movement is the thrust clearance between the crankshaft thrust faces and the bearing’s thrust surfaces (and any thrust washers or thrust bearings involved). The fillet radius is a geometric feature that helps reduce stress concentrations and aids oil behavior, but it does not determine how much axial play the shaft can have. Main bearings mainly provide radial support; end play is governed by thrust clearance, not the radial fit of the main bearings. So, neither statement correctly identifies what controls end play.