Is a forming tap better for blind holes?

       Broken taps and ruined threads on blind holes sound familiar? Plenty of machinists still struggle with chip packing at the bottom of holes. So should you pick forming taps for blind‑hole tasks?
     Traditional spiral flute cutting taps push chips upward out of blind holes. No matter how carefully you operate, tiny chips can get stuck. One subcontractor shared his data: processing M5 blind holes in aluminum alloy, cutting taps hit 1900 holes per tap with around 8 % scrap from trapped chips.
     Forming taps do not make chips. Threads are shaped by squeezing material instead of cutting it away. In the same aluminum blind‑hole test, forming taps reached 7100 holes, nearly quadrupling tool life. Thread surface finish got much better, and tensile strength went up 20‑24 %. You no longer need extra depth reserved only for chip space.
     Keep one key fact in mind: forming taps are not for everything. You need the correct larger pre‑drill size and good forming‑purpose lubricant. They will not work well for cast iron or other brittle materials.
     For stainless steel, aluminum and brass blind‑hole jobs, forming taps are absolutely worth trying to cut scrap and tool costs.
The KZF Threaded Tools Team is here to provide you with professional consultation.