Rc tapped hole drill size incorrect?

Hi all,


I'm trying to figure out what I have done incorrectly. I am trying to specify a 1/8 Rc (BSPT).

From the standard, the tappign drill size is 8.5mm
When I use the  hole wizard, the deafult setting is for a tappign drill at 7.9mm.
Does anyone know what I am doing wrong??

cheers,

Joe

SolidworksDrawings And Detailing