Hand Tools
Square Hole Drill Bit Adapter, 4pcs Mortise Square Drill Bit, Wood Mortising Attachment for Drill Press, Drill Bits Set for Woodworking, Mortising Set
This adapter is compatible with benchtop drill machines that have hand drill clip diameters ranging from 38 to 55mm (1.5 to 2.2 inches) The drill bit is available in sizes of 1/4 Inch (6.4mm), 5/16 Inch (8mm), 3/8 Inch (9.5mm), and 1/2 Inch (12.7mm)...
https://www.bizrate.co.uk/handtools/square-hole-drill-bit-adapter-oid40483299064.html