Simple Trepanning Tool

There are a number of ways in which large diameter holes can be cut in sheet or plate. One method is to chain-drill a ring of holes around the inside of the required circumference, break out the middle and file the hole to shape. Another is to use a piloted or centreless hole saw, available in standard diameters. Alternatively, tools known as 'tank cutters' can be used with either a brace & bit or a "Black & Decker". A central twist drill runs into the metal and acts as a pivot. These are not suitable for precision work however as the twist drill is inclined to wander.

This gives one time consuming method, one expensive method and another of dubious accuracy...

This little Trepanning Tool will cut holes of between Ø1" - Ø3" with great accuracy. In the process of 'trepanning' an ordinary cutting tool is powered along the circumference of the required hole and slowly cuts through, leaving the kind of chips/swarf that you we find when parting off.