Some fastening assemblies use a rubber grommet or washer for a specified sealing, cushioning or isolation function. Not every screw joint requires rubber, and the correct arrangement depends on the equipment.
For a sealed fastener, use the specified washer or seal, compatible materials and tightening instructions. A general cable grommet should not replace a purpose-made roofing or enclosure seal.
For vibration mounting, check load, stiffness, compression and any rigid contact path through the screw. Rubber under a screw head does not automatically isolate a machine. Verify the complete fastening assembly against its intended function.
