Drilling at a Slower Rate In general, it's best to drill through metal at the slowest feasible speed with a metal drill bit. Hard metals, such as steel, and bigger drill bits need even slower rates. Most metals may be drilled through at 3,000 rpm with a tiny twist bit (1/16 in. to 3/16 in.). For best results, use a torque wrench to keep the torque on your drill below 15 ft-lbs (20 Nm). Metal can break if overdrilled, so take care not to go too deep. The advantage of drilling slowly is that you don't heat up the metal being drilled. This can cause it to soften or melt, which can lead to failure of the connection. Drilling faster also uses less energy than drilling slower, so this is an environmental benefit too. Of course, if you want a really strong connection, you should drill deeper rather than slower. Drilling Metals - Best Practices When connecting metal objects together, it's important to avoid heating them up too much during drilling. This can lead to failure of the connection. If possible, drill into a cold piece of metal to get the most strength from the connection. It's also important to use a torque tool to make sure you aren't overdriving your drill. You don't want to destroy your drill because you thought it was a good idea to drive it hard when making a connection.