Vermont Tap & Die - 1/4-20 UNC, 3 Flute, Oxide Finish, Powdered Metal Spiral Point Tap - Plug Chamfer, Right Hand Thread, 2-1/2" OAL, 5/8" Thread Length, 6.48mm Shank Diam, 2B Class of Fit, Series 3712SM

Plug chamfers are the most commonly used chamfer and are designed for efficiently threading through and blind holes. They have 3 to 5 threads.

Oxide, also known as black oxide or steam oxide, is a surface treatment that prevents chip building, galling and welding on the workpiece. It is commonly used on low carbons, stainless steel and ferrous metals.

Powdered Metal (PM) is tougher and more cost effective than solid carbide. It is commonly used on highly abrasive materials including high silicon aluminums.