Be sure to use tapping oil before tapping. Drill a hole to the correct size, and place the tap in the hole, ensuring the tap is sitting at a 90-degree angle. Slowly turn the tap a few threads and back out to remove any loose material. Then, slowly tap further. Repeat this process until your hole is fully tapped to the proper ⅛-27 NPT thread pitch.
Please check out the installed video for drilling and tapping below:
How to Properly Tap https://www.youtube.com/watch?v=QUyNYxGYgGA