![]() Join 100,000+ CNC'ers! Get our latest blog posts delivered straight to your email inbox once a week for free. The moral of the story is to always check on critical parts like aerospace if there is any doubt. Some machinists had dealt with companies that never allowed form tapping of their aerospace parts while others insisted on it, or didn’t care. That thread concluded that there was no guideline suggesting never to form tap, but rather it was a function of the particular specifications for the part. Because no metal is cut away, the possibility of producing oversized threads is greatly reduced. ![]() Better thread gaging: Forming taps rearranges the metal in the hole to create the thread. After extensive Googling, I eventually found an interesting thread on Practical Machinist. Thread forming pipe taps are used to form internal threads by displacing the metal without producing chips in pipes and pipe fittings. Stronger threads: The grain flow of formed threads as a result of form tapping follows the contour of the thread resulting in greater thread strength. At best, Guhring suggested not using form taps in aluminum alloys with more than 10% Silicon. Prowling various tooling catalogs, I could find no mention of such a recommendation. I found this interesting because it was the first I had heard of it. ![]() Postscript: In a discussion about form taps, one individual suggested the not be used for aerospace applications because the threads are more brittle in certain alloys of aluminum. Read our article on rigid tapping pros and cons for more on that. You’re much less likely to break a thread mill, and if you do, it won’t be stuck in the hole the way a tap would be.Įncore Tidbit: Consider a tension compression holder even when rigid tapping. Last tapping tidbit: For the hardest materials, and especially when the cost of a broken tap is very very high, consider thread milling. Everbody I read suggests Moly-Dee is the one to choose. Check out our Drill Tap Size Chart and Calculator for the details–seriously good stuff there!įourth tapping tidbit: Use tapping fluid–your taps will thank you all most as much as they did when you pulled that thread percentage trick above. That all comes from selecting the right drill size. Third tapping tidbit: Would you like to know the ultimate secret to maximizing the life of your taps? It boils down to selecting a thread percentage that gives you enough thread strength while minimizing the torque that must be applied to the tap. Peck tapping is also an excellent way of clearing the long stringy chips often found when machining plastics and some other materials . Peck tapping is only called for with a cutting tap–no benefit to pecking with a form tap. For the most part, you will need rigid tapping to be able to peck tap because the tap has to get itself synchronized back to the same set of threads as it goes in and out of the hole. ![]() Peck drilling is familiar to most machinists, but peck tapping may be new. Second tapping tidbit: you can “peck” tap difficult holes. That information comes from tapmaker Titext via the link I’ve provided. That actually covers a surprisingly wide range of materials including a lot of steels. This list is longer than you might think, and includes wrought and cast aluminum and aluminum alloys, copper, brass, stainless steels, carbon steels, and zinc diecasting alloys.While many machinists may think form taps are only for aluminum, the answer to the quick question is you can form tap materials up until they have a hardness greater than 36 HRC, which is about 340 BHN. Generally, materials that produce a continuous chip when drilling are good candidates for thread forming. This includes light metals and light metal alloys as well as steels and other materials with tensile strength to 1200 N/mm 2 and hardness below about R C 35 – 40. Since the metal’s structure is cold worked along the thread profile, the threads produced are generally stronger and have a smooth, burnished surface finish.įorming taps must be applied in materials that cold form well. Rather, the process displaces the material to generate the thread form. Unlike thread cutting, no material is removed during thread forming. For ductile work materials, thread forming can provide better size control and stronger threads while improving tool life and productivity. The vast majority of threaded holes–more than 90%, according to one supplier of taps and other cutting tools–are produced using cutting taps.īut many of those threads could be produced using forming taps, which can provide multiple advantages. In the right application, thread forming can boost quality and throughput
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