Wedge:Place two inclined planes side by side .They will make a sharp edge and this simple machine is called wedge.A wedge is used to move things apart.Therefore,we can cut different things using an axe,knife,saw etc. Screw:We use screw to move things up and down,e.g we cna lift a car with one hand by just screwing a car-jack.A screw is also used to hold things strongly together e.g a bottle lid,wood screw,nut and bolt etc.The screw in the lid helps it to close a jar tightly.A screw in wood holds the pieces of wood together.
As nouns the difference between screw and wedge is that screw is a device that has a helical function while wedge is one of the simple machines; a piece of material, such as metal or wood, thick at one edge and tapered to a thin edge at the other for insertion in a narrow crevice, used for splitting, tightening, securing, or levering () or wedge can be (uk|cambridge university|slang) the person whose name stands lowest on the list of the classical tripos.
As verbs the difference between screw and wedge is that screw is to connect or assemble pieces using a screw while wedge is to support or secure using a wedge.