Dormer HSS Bright UNC UNC Hand Tap Straight Flute ANSI 1/4 inch x 20, size 1/4NO3. The most versatile taps for hand use or machine tapping in a wide variety of materials in through or blind hole applications. Available in 3 chamfer lenghts - taper, plug and bottoming. Premium substrate with bronze oxide body and shank reduces rust and corrosion. Bright finish flutes improve chip flow in soft or non-ferrous materials.