Where does the spring or lock washer go?

Seems most answers miss the question - when using a lock and flat washer TOGETHER, under the bolt head, in a tapped hole, not with a nut. The latter is self explanatory. But for a tapped hole I put the flat on the surface and the lock between the flat washer and the bolt head. The lock still works almost the same as without the flat, but with the flat beneath the lock the lock does not scar the surface of what you are bolting to. It it makes not difference if you scar the surface, then the flat with a lock is not necessary, unless your are bolting through a too-large hole in whatever you are attaching to the primary surface (eg; Headers to a Cylinder Head versus a Chromed Water gooseneck to an aluminum Intake Manifold or the like. The lock washer works by pushing up and down and stretching the bolt. Adding a flat washer under the lock does not diminish this stretching action. Happy washering!

Murf
December 2012

the flat washer goes against the head; the top of the bolt and the lock washer goes against the nut; on the bottom of the bolt.

Brian Baxter
November 2010

The flat washer goes beneath the head of the bolt. The purpose of the flat washer is to distribute the pressure of the bolt head evenly over the part being secured, and to provide a smooth surface for the bolt to bear on, making it less likely to loosen as a result of an uneven fastening surface.

The lock washer is installed against the nut. It applies a constant force between the nut and the part being attached and is what prevents the nut from loosening during movement or vibration of the parts.

JC
October 2007