A zero insertionextraction force integrated circuit socket including an insulating socket one side of which is formed with a receiving dent. The end mill is equipped with a series of sinusoidal cutting edges with a single long pitch arranged regularly or irregularly along the circumferential cutting surface. As an alternative, the method includes a step of determining that the combustor is ignited, when a change amount or rate of the exhaust temperature exceeds a predetermined value in a predetermined period from the outputting time of the ignition command. That channel has an opening on the surface of the form cylinder.