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Did I miss something Zee. Did Jo announce her retirement and I missed it??
The taper tap will remove the metal is several shallow depth cuts eg it takes about 6 turns until cutting fill depth, a plug will try to take it all of in one go so meeds more effort which with a small tap can break it.
Where to Use Thread Forming TapsMaterials particularly well suited for thread forming include aluminum, brass, copper, lead, stainless steel, carbon steel, cast steel, leaded steel and zinc. In general, any material which produces a stringy chip is a good candidate for cold forming threads. If the chips are powdery, the material may be too brittle. Forming taps generate threads without producing chips. The threads produced are much stronger than those created by cut taps because of the displacements of the grain of the metal in the workpiece. Cutting taps produce chips which may interfere with the tapping process.Thread forming taps are also known as: Fluteless Taps, Roll Taps & Cold Forming Taps.Major Advantages to Thread Forming1. Chipless Tapping – no chip removal problems in blind holes2. Stronger Threads – the grain flow of formed threads follows the contour of the thread in steel and stainless steel, resulting in greater thread strength3. Better Thread Gaging – forming taps create their own lead therefore the possibility of producing oversized threads is greatly reduced4. Stronger Taps – the absence for the need for flutes results in a stronger more solid tap5. Longer Tap Life – forming taps last 3 to 20 times longer because they have no cutting edge to dull6. More Efficient Production – longer tap life, less tap breakage and faster tapping speeds (up to 2x faster than cutting taps)7. Ideal for Non-Lead Screw Tappers – The ability to form their own lead makes forming taps well suited for NC machines or other machines without lead screwsGuidelines For Using Thread Forming TapsPre-Tap Hole Size - Thread forming taps require a larger pre-tap hole size than a cutting tap. Tapping with too small of a pre-tap hole size results in excessivetap wear, torque and possible tap breakageLubrication - Forming Taps require good lubrication. Cutting oils are generallypreferred because of their lubricity compared to water soluble coolantsStyles - Standard, pipe and STI