Longer Drill Life Carbide drills are made by combining tungsten particles with carbon and cobalt under high pressure and heat. This could be likened to a concrete post made up of sand and using cement as a binder. A carbide drill does not get dull because of wear like a steel drill does. It gets dull because the cobalt gets warm and it cannot hold the tungsten particles on the very fine cutting edges. Tungsten is a very hard metal and does not in itself experience much wear. During the actual drill stroke when the drill is removing material, some of the generated heat is taken away by the chips. After the hole is completed, it is absolutely necessary to remove the drill from the hole as soon as possible. Sitting in the hole at thousands of revolutions per minute generates heat that can only go into the drill bit. This is damaging to the binding strength of the cobalt, and as a result, some of the tungsten particles are released from the cutting edges of the drill. As this blunting proceeds, each succeeding drill stroke adds more heat to the drill. When the cobalt reaches a certain level of warmth, it deteriorates very quickly and can result in a broken drill if not changed immediately. The IDCT spindle is one in which only THE DRILL ITSELF is rotating at high speeds and is the only member which is stroking up and down. Because of the extremely small weight of the drill, it can be retracted from the drilled hole in 5 to 10 milliseconds. This allows only a small amount of heat to be generated and conducted into the drill. Another advantage the IDCT spindle has over conventional spindles is that the drill stands alone. It is NOT coupled to a motor armature, which can be a heat generator. Motor armatures, when hot, cause a flow of heat to go into the drill. This is probably the major cause of carbide drill breakdown in conventional spindles. Beyond the drill retraction rate and the drill isolation, there are other variables that affect the drill life. These are present in all spindles. They are: Drill design geometry. Depth of the hole being drilled. Type of circuit board material being drilled. The cobalt to carbide ratio in the make-up of the drill. The time in moving from a drilled hole to the next position. A longer time allows cooling of the drill but slows down the drilling. Sharpness of the drill at the start of drilling. A dull carbide drill will deteriorate very quickly because its dullness generates heat. Drill feed and speed parameters. Carbide drills are quickly destroyed by rotating them faster than the recommended peripheral velocity. The high impact of the cutting edges against the material being drilled knocks the tungsten particles off, making the drill dull. On high production circuit board drilling machines capable of 300 or more hits per minute, it has been estimated that the cost of the drill bits is 40-70% of the entire cost of drilling. Using the IDCT spindle, this cost is dramatically reduced by at least 4 times.