To tap threads into Steel is easier than Aluminium because aluminum is softer and the shavings can seize the tap causing the amateur to break the tap in the hole. Once a tap breaks in either metal it usually requires a professional to get it removed.
Tapping creates internal threads in a hole to accommodate a screw.
The proposed bolt determines the tap and the tap determines the drill size used.
Cutting fluid or lubricant helps the tap cut through the material more easily.
Choose the screw, as this determines the tap needed.
Drill the hole required by the tap, use a tap chart or most taps are marked with the required drill.
For larger holes, drill a smaller pilot hole first to guide the tap.
Select the tap based on the proper screw size and correct thread size.
Use cutting fluid or lubricant.
Cut the threads by turning the tap with the wrench.
Apply moderate pressure to turn until the tap starts to bite into the material.
Alternate between turning clockwise to cut threads and counterclockwise to clear chips.
Clear chips regularly from the hole to prevent the tap from jamming. Be careful not to force the tap; excessive force can break it.