Straight-flute taps have straight flutes parallel to the axis—the most traditional, general-purpose type: simple, rigid, and economical, for hand tapping and general shallow holes in short-chipping materials (cast iron, brass). Without active chip direction, they pack chips in deep holes or long-chipping materials, so they suit shallow holes or peck-tapping. Mainly HSS, some carbide. Choose by chip type: good for short chips, shallow holes, or hard materials; for deep blind holes or gummy materials, use spiral-flute taps.