This photo shows the pad having been drilled in the radial drill which is then used to hold the tap steady and central. This is achieved by fitting a pointed centre tool in the drill chuck and locating this in a small conical hole on the top face of the tap. As the tap is turned to form the thread in the hole the centre tool is gently lowered by hand feeding the drill chuck. The drilling machine is only used to centre and stabilise the tap - not to drive it in any way.
Credit: Dick Bellchambers, 9 August 2005