Q&A for How to Use a Tap

Make sure that the hole and tap are lubricated and the hole is free of debris. Check for chips on the tap itself, and check the working conditions of your tools before and during use. The last thing you need on a job like this is to have a tap sheared off inside the hole.

You should ask for help from a plumber.

Same guidelines as outlined above: check size of screw you want, obtain appropriate tap, pre-drill, use tap with tap handle and turn counterclockwise 1/3 for every full turn so that tap does not get stuck with debris.

Do a Google search for your answer. You will find tables with drill and tap sizes for the hole size you want to thread. Also, when cutting your threads, use a cutting oil.