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"With the Turbowhirling concept, Horn sets up the tool using roughing and finishing inserts. e roughing inserts do the majority of the cutting, taking the thread down just short of the finish diameter. e finishing inserts then clean up and cut the threads to their specified depth and profile. Because the finishing inserts are removing signifi- cantly less material volume, tool life is increased signifi- cantly. e tool body for Turbowhirling is the same as for conventional whirling, as is the cutting data." Using this specialized system, the inserts can be designed to better perform each assigned task. e roughing inserts, because they are not generating a functional surface, can be formulated to tolerate quite a bit of wear. is allows the finishing inserts to generate the functional surface with a minimum amount of stock removal, improving their tool life. In effect, the combina- tion of roughing and finishing cutters allows the whirling tool to perform rough and finish operations in a single pass, thus improving throughput. e arrangement of the roughing and finishing inserts depends on the number of inserts that the cutter can accommodate. On a nine-insert cutter, three inserts might be used for roughing, with six inserts to cut the thread to the final size and finish profile. e seats in the cutter body are standard, so the inserts can be arranged in various ratios to accommodate the application. For some applications, if the whirling toolholder has sufficient pockets, the cut can be further divided with the use of semi-roughing inserts, effectively combining what would take three passes into one. Increasing tool life is an important goal for this whirling system. Generally, because the finish inserts are removing relatively small amounts of material, the roughing inserts can be indexed three to four times before the finish inserts need to be exchanged. "Shops that have experience in thread whirling will find that using the Turbowhirling concept is no different," Mr. Foschaar says. "e difference between the two cutting methods is the geometry and arrangement of the index- able inserts. e roughing inserts are ground for roughing and the finish inserts are ground for finishing. To prevent confusion with building the tool, the roughing inserts receive a flash coat of TiN to visually distinguish them from the finish inserts. It's a simple, yet effective way to make sure the inserts are positioned in the correct pockets." e whirling attachments for Turbowhirling, likewise, are standard. If an attachment can be used for conven- tional whirling, it will work for Turbowhirling. Moreover, if the attachment can accept a quick-change cutter, they too will work for Turbowhirling tools. "Basically, the only difference between conventional whirling and Turbowhirling is the performance from lowered cycle times and longer tool life," Mr. Foschaar says. :: The tool path for conventional thread whirling (left) is relatively simple compared with the significantly more complex tool path that is generated for rotary whirling (right). CUT TING TOOLS 32 PRODUCTION MACHINING :: DECEMBER 2017