This gas compression spring is approx. 53 cm long and protrudes beyond the core bit; after drilling, if the segments have clearly penetrated the substrate, the centring is removed. Field of Application: The gas pressure spring with a specially designed machine chuck fits perfectly into a machine spindle with a 1/2 inch female thread. These 1/2 inch threads are mainly found in the form of a combination spindle (i.e. inside 1/2 inch, outside 1 1/4 inch) in core drill motors.