Originally Posted by
velopig
I was a tool and die maker by trade and I would strongly suggest not to start fooling around its files and misc. thread files. Find a bike a bike shop with proper head tube die threader to clear up the fork. I work as a mill right as well and still it would be a last choice to start fooling around with a needle file.
Personally I'd rather take my chances with my own experience and knowledge than having some 20 something at the LBS who's never seen a threaded headset attempting to run the die over it. From the photos, he basically has to clean up the first thread and kind of make a higbee cut and he's good to go.