In wire electrical discharge machining, also known as wire-cut EDM, a thin metal wire is fed through the work piece, which is typically, but not always submerged. Brass is the most commonly used type of wire. The wire is held between diamond guides, and if the work piece is submerged, water is most commonly used. The water helps flush away the cutting debris- this is important because wire EDM is often used to cut very intricate parts, and machine calibration is very sensitive. Tiny bits of metal in the water can interfere with the process by filling the gap between the part and the wire eliminating the spark, so filtering is critical for submerged wire EDM machines.