Abstract: Coolant is supplied through a main delivery line and a conduit bored in the toolholder by coolant pumps. The coolant then enters into a ring having two opposite ball jets from which it is simultaneously conveyed in two concentrated streams on to both the grooves of the twist drill. Each of the streams of the coolant is directed at the respective beginning portions of the grooves. The ring is rotatably set up on the toolholder and is adjustable in the required position. The ball jets are swingable and securable in the required position in the ring by retaining screws.