![]() Special taps are usually designated NS, indicating a special thread size. There are other standard tap designations such as NPT or NPTF for tapered pipe threads. Available in straight and spiral flute, spiral point, and forming. The only problem with this is you must have an insert for each thread pitch which is way to expensive to use in the home shop. Standard taps are either standard coarse series threads NC (1/4-20), fine series threads NF (1/4-28) or extra fine series NEF (1/4-32). For high-performance threading, select Kennametal’s High-Speed Steel taps. ![]() At work we use thread forming inserts on the lathe that actually cut the top of the thread behind the one being cut normally which makes a very smooth thread on the top. The biggest cause of rough threads is running the work to slow while cutting the thread and no lubricant. Cobalt chrome is one of the more difficult materials to tap because it is so hard, and, typically, a solid-carbide tap is used. Also one single point tool is a lot cheaper than a bunch of dies. While form taps can be applied in some stainless, we can’t form tap in the medical industry because there is a small gap in the truncation on the minor diameter where bacteria can collect, Goodman noted. Most threads I've seen cut with dies that weren't perfectly sharp looked worse than any cut with a single point tool. With a little practice you can make a thread with a single point tool look as good or better than any done with a threading die. ![]() Tap life is much improved over conventional high speed steel. Some of the big stuff gets real expensive real fast.Practice makes perfect Dog. Carbide taps are excellent in soft abrasive materials. In my shop threads done with dies look much better and you ain't as likely to get cut on any jagged edges! I expect there are places you can go single point that you have a hard time with a die. The workpiece is hard Form taps are suitable only for soft and malleable metals such as soft steel, some stainless steels, aluminum, copper, brass, and lead. Surface Footage 127 RPM SFM X 3.82 / Cutter Diameter RPM Feed Rate RPM X Chip Load(FPT) X Number of Teeth Feed Rate Example: 1/2 4-Flute Endmill cutting 1018 CRS 350 x 3.82 /. ![]()
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