actuation of the pressure jaws 20 as shown in fig1 by removing the bracket 16 away from the tool to the right in the direction of the arrow a corresponding piece of fiber bundle can protrude beyond the frontmost clamping jaw 17 as shown in fig1 the two pressure jaws 18 and the fixed pressure jaw 20 is released as shown in fig1 by then moving the bracket 16 towards the tool 1 as shown in fig1 the fiber bundle 4 will at the end touch the tool 1 in that the mandrel 3 will be situated among the fibers the tool is now heated and the fibers begin to melt at the same time the bracket 16 is moved a further distance towards the tool as shown in fig1 whereby further fiber material is fed on a continuous basis during the melting for the formation of the bottom normally a surplus of material is carried forward in order that an additional bottom part 6a is formed as shown in fig1 this serves the purpose of ensuring that the final bottom 6 is always complete which is a safeguard against the fibers working loose in that they are incorporated in the bottom after heating the fiber material is cooled while at the same time the pressure jaws 18 are released and the fixed pressure jaw 20 is actuated in this position the bracket 16 can be moved to the right as shown in fig1 in that the fiber bundle 4 remains in contact with the tool once the cooling is completed the knife 21 is moved downwards for cutting the fiber bundle as shown in fig1 and the finished brush head 5 6 can.