Smittiferous
Well-Known Member
[MENTION=42187]Murph_BTK[/MENTION] For boring the round vents: 28mm spade bit. Start one side, go 1/2 to 2/3 the way through, then finish it from the other side else it explodes through and probably make a mess of the other side. Spade bits have a pilot tip that'll penetrate the whole way through so you'll easily see where you're drilling.