Helicoil
Over a long period of time the internal thread on a piece of metal can deteriorate, smoothing itself out until it reaches a point where the screw or plug is no longer able to stay in place. In some cases this causes a panel to vibrate its way lose, in others it can affect key components like spark plugs that rely on the internal thread to hold the plug in the correct place inside the cylinder. In order to restore the internal threading HeliCoil kits have been made that allow you to create a new internal thread and to restore the fitting. Specific HeliCoil Plus spark plug thread repair kits are a top investment from the perspective of any experienced mechanic, allowing you to create a new internal thread using a HeliCoil insert that will then accept the spark plug or screw.