Limits for Bow

When dealing with shafts and tubes, it is vital that not only are the ends square with each other, but also the centreline of the complete shaft or tube is straight. If the centre line of the shaft is not straight, then the item is bowed. When the shaft or tube is rotating, especially at a high speed in a bowed state, there is the risk of vibration, which can lead to mechanical failures, loosening of fasteners and fatigue.

All cylindrical items can be given a limit to the amount of bow permitted. For example, a drive shaft, which rotates about 1500rpm may have a limit of 0.25mm bow over the length of the shaft. This ensures that, within the limits of production, the drive shafts are effectively straight, giving the least possible vibration.