Abstract: An electrode is secured and sealed in an insulator having a bore. The electrode has a shaft and an end plate, with the shaft having a cross section smaller than a cross section of the bore and the end plate having a cross section larger than the cross section of the bore. The shaft of the electrode is inserted into the bore and secured in the bore. A compressive force is applied between the end plate and an opposite end of the electrode, and an electrical current is applied between the end plate and the opposite end of the electrode to heat the electrode while the compressive force is applied. The electrical current and the compressive force are removed after being applied for a time sufficient to heat and expand the electrode so that, upon removing the electrical current, the electrode contracts to establish a seal between the electrode and the insulator.