Abstract: In a heat drilling process for tunnels, deep well and exploration boreholes, only a gap defining the outer profile of the tunnel or borehole is melted down. The drill core surrounded by this gap initially remains and is then extracted at intervals via the melted zone. It is expedient for the drill core to be sheared off and extracted continuously after it has passed a cooling zones. The height of the drill core which first remains in the borehole is determined such that the molten rock can be pressed into the drill core, whereby for this pressing in the necessary pressure is maintained essentially constant independently of the depth of the borehole concerned.