![]() Coatings include titanium nitride, titanium carbonitride and diamond-like amorphous carbon. That’s why the Innoform tap line has specific combinations of geometry and coatings to thread standard steels soft steels hardened steels stainless steels cast aluminum wrought aluminum alloys and non-ferrous metals and materials with limited ductility. However, suitable materials react to cold forming in different ways. As a rule of thumb, if a continuous chip is created when drilling, then the material is likely a good candidate for cold forming the threads. Tapping via cold forming is appropriate for materials with tensile strength less than 1,200 N/mm2 and fracture strain of 5 percent. Lessons on the Journey Toward Shop Automation ![]() (See animation demonstrating this thread-forming action in the Learn More box above.) Because the material is compressed and its grain is redirected, rather than cut or interrupted, strength at the thread flanks and root is increased. This material displacement creates the signature claw-shaped seam on the thread crest. Their lead taper produces the thread profile, gradually flowing material from the thread crests, along the thread flanks and into the minor diameter area. The taps have a polygonal cross section with forming wedges that mirror the thread profile. Instead, they displace material to form the shape of the thread. Unlike thread-cutting operations that use fluted taps, cold-forming taps do not make chips. Alan Shepherd, Emuge’s technical director who provided the background for this article, explains how cold-forming taps create internal thread profiles and suggests applications for which thread forming is particularly well-suited. ![]() This cold-forming tap program is said to be the first to target such an array of individual material groups. For example, Emuge (West Boylston, Massachusetts) has developed its Innoform line of cold-forming taps, which is available in 30 geometry and coating combinations for use with seven material groups. However, recent tap geometry refinement and advances in coating technologies have made this chipless operation suitable for a wider range of workpiece materials. Shops have been cold forming internal threads for quite some time. A cut thread, shown at the right, interrupts the grain. The left image shows how cold forming compresses and redirects material grain, increasing thread strength.
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