A spindle assembly configured to be assembled in a machining device, the spindle assembly having a rear end and a front end, with the front end being proximal to a tool clamping system of the spindle assembly, and the rear end opposite to the tool clamping system, the assembly comprising: a rotating shaft; a bearing assembly (103; 105), comprising a front end bearing assembly and a rear end bearing assembly, configured to support the rotating shaft and to enable high-speed rotation of the shaft within the spindle assembly; a turbine operatively connected with the rotating shaft, the turbine configured to rotate the rotating shaft; a hollow housing to mechanically support components of the spindle assembly, the hollow housing comprising a plurality of passages to allow flow of high pressure fluid provided by the machining device; and a front cover located in front of the hollow housing, the front cover comprising: a first group of passages, fluidly connected to the plurality of passages of the hollow housing, to allow the high pressure fluid to flow from the passages of the hollow housing towards the blades of the turbine and rotate the turbine; a hollow space (310; 311) located substantially at a center of the front cover to provide free space for the blades of the turbine; openings located at the front end of the front cover to allow low pressure fluid to flow from the hollow space out of the spindle assembly; characterised in that the spindle assembly further comprises: a second group of passages extending from between the blades and the front end bearing assembly, to the front end of the front cover to allow collection of low pressure fluids that flow towards the rear end of the spindle assembly after hitting the blades of the turbine and to direct these fluids towards the front end of the front cover and out of the spindle assembly, wherein the turbine is placed between the front end bearing assembly and the front cover. a rotating shaft; a bearing assembly (103; 105), comprising a front end bearing assembly and a rear end bearing assembly, configured to support the rotating shaft and to enable high-speed rotation of the shaft within the spindle assembly; a turbine operatively connected with the rotating shaft, the turbine configured to rotate the rotating shaft; a hollow housing to mechanically support components of the spindle assembly, the hollow housing comprising a plurality of passages to allow flow of high pressure fluid provided by the machining device; and a front cover located in front of the hollow housing, the front cover comprising: a first group of passages, fluidly connected to the plurality of passages of the hollow housing, to allow the high pressure fluid to flow from the passages of the hollow housing towards the blades of the turbine and rotate the turbine; a hollow space (310; 311) located substantially at a center of the front cover to provide free space for the blades of the turbine; openings located at the front end of the front cover to allow low pressure fluid to flow from the hollow space out of the spindle assembly; a first group of passages, fluidly connected to the plurality of passages of the hollow housing, to allow the high pressure fluid to flow from the passages of the hollow housing towards the blades of the turbine and rotate the turbine; a hollow space (310; 311) located substantially at a center of the front cover to provide free space for the blades of the turbine; openings located at the front end of the front cover to allow low pressure fluid to flow from the hollow space out of the spindle assembly; characterised in that the spindle assembly further comprises: a second group of passages extending from between the blades and the front end bearing assembly, to the front end of the front cover to allow collection of low pressure fluids that flow towards the rear end of the spindle assembly after hitting the blades of the turbine and to direct these fluids towards the front end of the front cover and out of the spindle assembly, wherein the turbine is placed between the front end bearing assembly and the front cover. a second group of passages extending from between the blades and the front end bearing assembly, to the front end of the front cover to allow collection of low pressure fluids that flow towards the rear end of the spindle assembly after hitting the blades of the turbine and to direct these fluids towards the front end of the front cover and out of the spindle assembly, wherein the turbine is placed between the front end bearing assembly and the front cover.