Century Metric Plug Tap 97309 Precision Cut Threads are accurately formed for consistent, exact threading. Heat-treated and tempered for file-hard threads, resulting in a longer, more useful life. Designed for hand-cutting applications. For use with tap wrenches to cut internal threads. 75% Thread Engagement. Plug style is the most commonly used style of tap, with 3 to 5 Threads and a Chamfered End. Use No. 20 drill.