I regularly drill 11mm sq blanks on my lathe using a centre-point bit with no problems. Well... in all honesty that's not quite true. But I do have a better than 90% success rate.

Having said that, I should point out that I ruined a LOT of blanks until I refined my technique. What can I say, except offer the same old advice as usual? A properly sharpened bit, slow speed, frequent scavenging and good support of the blank. (Oh... and actually applying that advice, not just nodding in agreement then trying to break the world speed record for bludgeoning a hole through your next blank. )