Stripped bolt on thermostat housing

So, as I was changing out the thermostat that seemed to be sticking (Jinma 284) one of the housing bolts snapped right off, leaving the threads in the lower part where the thermostat rests.  While drilling out to retap, the drill bit floated a bit and ended up off center. So, I just drilled out a bigger hole and put a longer bolt and nut in as a replacement. Seems to work just fine.  What seemed odd was how soft the metal was to drill through!  Or I had a heck of a good bit!  Is the Chinese metal always this 'soft'?