Tapping

When Tapping you must drill a hole smaller than the final hole, typically with a numbered, not a standard sized, drill bit. To find this bit this you would use a Size Chart. For metric theres a nice trick: You take your final size and subtract the pitch. Most of the time metric is standard pitched so you can use a Metric Thread Chart to look that up. Ex: M6, standard is 1.0, use an M5 to drill your hole