BTW,
Make sure that the hole you drilled was large enough. it's easy to bust a tap if your tapping a hole that's too small.
use 2.5mm or .0984" for 3mm tap
use 3.3mm or .1229" for 4mm tap
use 4.2mm or .1654" for 5mm tap
Consult this for more info...............
http://www.engineersedge.com/tap_drill_chart.htm