Carbide Cutter Three Blade Counter Sink by Yu Xuanjie 1.00" / 25.4mm with .3185" / 8mm Hole

Will Fit a 5/16" Short Drill +/- a few Thousandths or 7.9mm +/- 

Can be used independently to face without a drill bit.

Premal's Tips:

Use shim stock wrapped around to secure drill bits smaller than 5/16".