Threading Technology – Clamping Technology 520

205 Roll Form Taps UNC UNF M MF G STI SELF-LOCK Tech. Info v c Product Finder 2.13 Cold forming and torque Technical data of the workpiece material Not all materials are suitable for cold forming. For that, they must show a minimum value of ductility and must not exceed a certain maximum strength. Suitable materials usually have a tensile strength of less than 1400 N/mm 2 and a minimum fracture strain of 5%. In addition, different materials and their alloys lead to very specific flow properties and strengthening characteristics. Obviously, wrought aluminum, high-strength steel or stainless materials will react in very different ways. Torque Torque, in the cold forming of threads, depends mostly on the workpiece material, the thread size, lubrication and thread hole preparatory diameter, as well as on the geometry and the coating of the tool. The influence of the preparatory diameter on torque is shown in the following diagram. 9,15 10 15 20 9,20 9,25 9,30 9,35 9,40 InnoForm, M10-6HX Material 1045 n = 350 rpm Preparatory diameter [mm] Preparatory diameter for EMUGE roll form taps M t [Nm] The following diagram demonstrates the difference in torque between thread cutting and cold forming. Parameter 10% 100% 100% Torque Cold forming Thread cutting M3 Thread size M16 soft Material high-strength good Lubrication bad 2.14 Cold forming as a production process The cold forming of threads, according to DIN 8583-5, belongs to the pressure-forming processes. The internal thread is produced by the impression of a helical sequence of thread teeth into the formerly prepared thread hole, the desired profile is formed by pressure. A roll form tap is provided with a lead taper and a cylindrical guiding part. The thread helix runs on through both parts. If you look at a cross-section of the tool, there is a polygon shape to be recognized at a right angle to the tool axis. This polygon shape provides forming lobes which carry the effective thread profile. The lead portion of a roll form tap is made as a lead taper, in which the helical thread line is continuously increasing in diameter. In the cold-forming process, the lead taper produces the thread, the forming lobes penetrating the workpiece successively in a radial direction by forming the thread. During this process, the workpiece material “flows” from the thread crests along the thread flanks into the area of the minor thread diameter. This creates smooth flank surfaces and, in the minor diameter area, the typical space pocket. The cylindrical guiding part of the roll form tap makes the surface of the produced thread even smoother, and serves to firmly guide the tool axially. Depending on the workpiece material, the essential advantages of cold forming include excellent surface quality but also increased static and dynamic strength of the thread. The length of the thread to be produced is not limited by chips which need to be removed, so process safety is extremely good. The excellent self-guiding characteristics of a roll form tap prevent axial “miscutting”. The extraordinary stability of the tools is very helpful, especially with small diameters. Demonstration workpiece Roll form tap