Most broken taps come from three causes: an undersized hole, a tap entered crooked, and swarf packing the flutes. The tapping drill size is published for every thread and is not a place to improvise.
Back the tap off regularly to break the chip, use cutting fluid generously, and start with a taper tap. In a blind hole, withdraw and clear before the flutes fill.
The questions welders ask
Are spiral taps better?
For machine tapping and blind holes, yes — a spiral-flute tap lifts chips out of the hole instead of packing them in, which removes the commonest cause of breakage. They cost more and are less tolerant of being pushed by hand at an angle.
Last reviewed 2026-08-14