Rubber Grommets and Gaskets
A grommet is any kind of ring, eyelet, plug, washer, or packing that seals or insulates a hole or joint in machinery. Grommets can be rubber, plastic, metal, graphite, fibres or ceramic composites. Examples of use are: to ground electrical wires where they pass through a metal wall; sealing pipe sections; preventing gases or liquids escaping; and many other industrial applications. A gasket is a ring for packing connections or sealing joints in machinery. Gaskets can be rubber, metal, rope, and other materials such as those used for grommets. You can see that there is a considerable overlap in the meanings and functions of grommets and gaskets. Indeed, many sellers and consumers use the words interchangeably. They may also call them rings, plugs, sealers, etc. For this reason, be sure of exactly what you are after so that the names do not mislead you into making a wrong purchase. For example, if it's for an exhaust system, go for heat-resistant gaskets, not rubber grommets. The variety of shapes and sizes of rubber grommets, gaskets and other types of hole sealers covers every imaginable vehicle. Look up your vehicle's specifications or ask a qualified mechanic to be sure.
Electrical Seals, O-Rings and Gaskets
A special use for grommets, gaskets and their cousins, the O-rings, is in industrial power transmission. The purpose is to seal holes where electrical wires and cables pass through metal walls and plates, such as the firewall in a car, firstly to ensure the safety of people. It also prevents current leaking, which damages the machine, and also ensures that the electrical system works correctly.
Exhaust System Grommets and Gaskets
Whatever vehicle you are servicing, all have an exhaust system that needs various points sealed. The reasons are: to tightly seal connections and help improve performance; to prevent deadly toxic exhaust gases, eg. carbon monoxide, from entering the cabin or reaching people; and to prevent exhaust bypassing the catalytic converter and being lost and wasted. This applies to cars and trucks, boats, motorcycles and all other combustion engines. Exhaust is very hot; therefore, the gaskets must be made of durable, heat-resistant materials. These include embossed steel, graphites, special fibres, ceramics and others.