![]() A cut tap disrupts that grain structure, creating a weaker thread.”Īccording to Walter’s Nehls, another benefit of form tapping is “better economy in the manufacturing environment. That compression produces a much denser grain structure, so the threads are stronger. “A form tap actually compresses that grain structure to create the thread profile. “It has to do with the material’s grain structure,” Gennuso said. In other words, the forming process produces the high static and dynamic tensile strength of the thread because of the workhardening. According to Machinery’s Handbook, that’s because the grains in the metal are unbroken in a formed thread and the displaced metal workhardens. “If all the variables are in place, a form tap can outlast a cut tap 30, 40 or even 50 to 1,” YG-1’s Zaitoon said.įormed threads are also stronger than cut threads. ![]() Form taps are more stable when threading than cut taps, which must have large flutes to evacuate chips. This means form taps are more rigid and less prone to breaking. ![]() The tap can be applied in steels up to 40 HRC.Ī form tap has a larger tool cross-section than a comparable cutting tap. OSG’s OIL-S-XPF form tap creates threads in 4120 alloy steel bar stock used for testing. The form tap can run unattended until it reaches the end of its tool life there’s no need to pause the machining operation.”įorm tapping is particularly effective for deep-hole tapping, 3 diameters deep or more, where it can be a challenge to remove chips. “Cut tapping can cause ‘birdnesting,’ which means the operator has to stop the machine, clean out the chips and start again-repeatedly-throughout the day. “In a lot of cases, depending on the material, form tapping is better for high-volume production,” OSG’s Gennuso said. The biggest benefit of roll tapping is that no chips are created, eliminating chip handling and all the cleaning, maintenance and equipment it encompasses. As long as the thread profile is 10 tpi or greater, you should be able to form it.” The limit is about 10 tpi, or 2.5 pitch in metric. “A fine pitch thread is easier to form because there is less material to displace. ![]() “There is also a limit on the pitch,” said Pat Nehls, product manager for Walter USA LLC, Waukesha, Wis., which offers the Protodyn CAP and Protodyn S Synchrospeed thread formers. Larger tools produce more friction and require more machine horsepower. When form tapping titanium, a lot of that heat penetrates the tool and causes premature failure.įorm taps are typically less than 3⁄4 ", or an M20, in diameter. Because forming doesn’t create chips, the heat must go into the tap or the material. During a tapping operation, heat enters the workpiece, tap and chips, he explained. “In addition to its high tensile strength and low ductility, titanium has very low thermal conductivity, meaning that it doesn’t absorb heat very well,” Gennuso said. Brittle materials, such as cast iron, do not flow well and cannot be form tapped. Material with a tensile strength of 160,000 psi and a maximum hardness of 36 HRC is about the limit for form tapping, although form taps for some materials up to 40 HRC are available.Ī range of metals can be form threaded, including aluminum, stainless steel, carbon steel, titanium and nickel. ![]() He estimates the ratio of cut taps to form taps used is about 100:1.įorm tapping requires a workpiece material that can actually flow to create the thread profile. But whether they call it form tapping, cold form tapping, thread forming, cold roll forming, roll forming, thread rolling, roll tapping or cold roll tapping, many metalworking professionals are unfamiliar with, according to Peter Gennuso, applications engineering supervisor for OSG Tap & Die Inc., Glendale Heights, Ill.Īl Zaitoon, marketing manager for YG-1 Tool Co., Vernon Hills, Ill., agreed that cut taps are more accepted and better understood. The process of displacing metal instead of cutting it is called many things. When the application is right, form tapping provides real production benefits. ![]()
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