What would be the best way to enlarge a hole in a turbo flange?

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I got this GT3071R turbo that has a T25 flange.  The exhaust manifold I have also has a T25 flange but the holes were tapped for 10mm, 1.5 pitch instead of 8mm, 1.25 pitch.  The problem is that 10mm studs won't fit through the holes in the turbo flange here.The Garrett specs for the through holes on the T3 flange is 11.2 mm (approx. 7/16"), my T25 flange has 9.00 mm holes.I have a drill press, can I just use a 7/16" drill bit to enlarge the holes or is there something better that I should use to enlarge the holes?Thanks in advance for any help.
Reply:If they need to be drilled and tapped, which is preferred, then you need to use the appropriate size drill for the tap. Std, metric and NPT are on this chart: http://www.kramerusa.com/DrillTapChart.htm If you use your drill press, grab a small level and level it both ways. Also make sure your drill press table is level. Clamp it down and drill it.John -  fabricator extraordinaire, car nut!-  bleeding Miller blue! http://www.weldfabzone.com
Reply:Originally Posted by MicroZoneIf they need to be drilled and tapped, which is preferred, then you need to use the appropriate size drill for the tap. Std, metric and NPT are on this chart: http://www.kramerusa.com/DrillTapChart.htm If you use your drill press, grab a small level and level it both ways. Also make sure your drill press table is level. Clamp it down and drill it.
Reply:That's a nice cast iron manifold, where did you get it and for what application?John -  fabricator extraordinaire, car nut!-  bleeding Miller blue! http://www.weldfabzone.com
Reply:Originally Posted by MicroZoneThat's a nice cast iron manifold, where did you get it and for what application?
Reply:Looks good. I prefer to use the cast manifolds for reliability. I have another source for cast manifolds, greater variety, and possibly less cost. How much are they from TSP?John -  fabricator extraordinaire, car nut!-  bleeding Miller blue! http://www.weldfabzone.com
Reply:$309.95 from Treadstone.  I paid $280.00 shipped, it was sold by an Audi forum member, brand new, never used.
Reply:Nice - that's a good price!John -  fabricator extraordinaire, car nut!-  bleeding Miller blue! http://www.weldfabzone.com