Grommet
This is the flexible pass-through element that prevents the edge from cutting the insulation where a cable passes through a hole in sheet metal. With vibration the sheet edge works like a blade and cuts the insulation over time, creating a short to chassis. A grommet removes this contact point completely.
When a hole is drilled, the edge stays sharp and burred. The cable moves continuously over this edge with vibration; friction that at first only scratches the surface reaches the conductor within months. The result is usually a blown fuse or an unexplained interruption.
- Order of work: first the hole is deburred and painted against corrosion if necessary, then the grommet is fitted, and the cable is passed through last.
- Size: the grommet must suit the sheet thickness and the hole diameter; a loosely seated grommet comes out with vibration.
- Alternatives: edge protection profile is used on long edges and a rubber bellows on dense bundles.
- Sealing: if the pass-through is in a cabin or box wall, the grommet is also expected to act as a moisture barrier; a sealed gland is preferred if necessary.
It is a detail that is easy to skip during installation and hard to find afterwards. Put checking for a grommet at every metal pass-through on your checklist.
Context in which this term is used: Installation, redundancy and field continuity