Answer: Galling occurs when metals slide against each other under high pressure. As friction causes the temperature of the metals to increase, molecular bonding increases, eventually resulting in gross damage or seizing. Higher speeds and surface pressures, high surface finishes, poor lubrication, and similar material hardness all increase the likelihood for galling to occur. Galling can be avoided by good lubrication, and proper specification of thread finish and nut materials. Steel nuts are appropriate for low rotational speeds where good lubrication is available; otherwise, they should be avoided. For higher rotational speeds or limited lubrication, either plastic or bronze nuts should be specified according to their load capacity.
