![]() For example, it is possible to thin the chip too much when tapping. Another way to tap more effectively is to manage chip thickness. “Very often, the design of the part forces the use of taps with short chamfer lengths.” “Taps with smaller chamfer lengths are usually used to keep the difference between hole depth and thread length to a minimum,” Haenle said. Unfortunately, there may not always be a choice. Shorter chamfer lengths, such as in bottoming taps, wear faster and should be avoided, if possible. “When comparing chamfer lengths of four threads or fewer, the tool life will double for every half thread added to the length.”Ĭlearly, increasing chamfer length in taps is desirable. “Chamfer lengths have a huge impact on tap life because they affect chip load,” Miskinis explained. Effectively, more teeth are cutting the thread, similar to a single-point threading tool taking multiple passes. To provide more options, tap manufacturers have added a few more forms, including a form consisting of a two- to three-thread length, sometimes called semibottoming.Īdding length to the chamfer distributes the chip load over a longer cutting face. There are three common lengths of tap chamfers: taper at 7-10 threads, plug at three to five threads and bottoming with one to two threads. “The load during the cutting process is distributed over a longer cutting edge with a lower chip load.” ![]() Peter Haenle, president of Guhring Inc., Brookfield, Wis. “Basically, a longer chamfer length means longer tool life,” said Dr. With smaller space comes the risk of packing chips, which can lead to broken taps.” “More flutes on the same circumference means smaller flutes, both in width and depth. “More flutes means there is less space for chips as they are cut,” said David Miskinis, senior application specialist, holemaking for Kennametal Inc., Latrobe, Pa. However, for tapping this advice would probably be wrong. This jives with standard metalcutting advice, which is to always use a maximum number of flutes. For example, a 4-flute tap would have half the chip load per tooth of a 2-flute tap. With more cutting faces, the load on each tooth is reduced. With every flute added to the tap, a cutting face is added. One approach might be to use taps with more flutes. As mentioned earlier, this is not possible when tapping but the chip load can be altered through tap selection. Defined as the load induced on any one cutting edge, chip load is typically controlled by altering the feed rate. L owering the chip load can eliminate premature wear on a tap. Tapping problems can be simplified and reduced by understanding tool geometry and what taps are best suited for a given application. ![]() However, while tapping can be tricky, it is not beyond understanding. ![]()
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