Eye lifting nuts are used to connect components of mechanical equipment for lifting, hoisting and suspension operations. Their working principle is to use the screw holes and threads at the bottom to connect with threads of the same specification. By connecting with threaded studs, eye lifting nuts can easily lift equipment and machinery of different specifications, models and weights.

The surface treatment of eye lifting nuts usually includes processes such as electroplating and hot-dip galvanizing. After electroplating, deoxidation treatment shall be carried out. The test methods for mechanical properties and chemical composition of relevant materials must comply with the provisions of GB 699. There are no relevant industry regulations on the surface treatment of eye lifting screws, but surface treatments such as galvanizing passivation can be applied.

Threads shall be sampled and inspected before delivery. Thread gauges, smooth limit gauges and universal measuring tools are generally used for measurement, and the measurement error shall not exceed the provisions of the standard. Finished eye lifting screws must be fully forged. Normalizing treatment must be carried out during forging, and oxide scale formed after oxidation shall be removed. The grain size of finished products tested in accordance with YB27-77 shall not be lower than Grade 5. Overheating, cracks and other defects are not allowed in finished forgings.