The weight indicator is generally considered to be the most important instrument on a drilling rig. An integral part of the hoisting mechanism, it helps the driller to drill a straighter hole, enables him to achieve the maximum amount of footage from each bit, and is absolutely essential for delicate operations like milling, coring, cutting and fishing.
Drill bits are expensive. And so is the trip time to change out a bit. But drill bits will last longer and drill faster when the correct weight is used. Maintaining the correct weight will also help the bit rotate in its true vertical axis.
With the proper number of drill collars stabilizing the bit, and the correct weight to keep the drill pipe tension, the bit will drill a rifle-bore extension of the well in spite of forces that tend to deviate the hole. However, when too much weight is applied to the bit with insufficient drill collars, the string will be in compression and perhaps cause the drill string to bend, this practically ensures a deviated hole, plus it accelerates bit wear and slows the rate of penetration.