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Shoulder milling cutter meets tool steel demands: machining tool steel is very hard on cutters--often breaking teeth, adding to production time. But the machinists at ThyssenKrupp Presta found a solution with a new shoulder milling cutter.

Typically in tool manufacturing, small quantities of work pieces are processed and the work piece material is hard and tough, so high precision and process reliability are vital, as is the case at ThyssenKrupp Presta.

The company supplies extrusion components to the automotive industry, as well as manufacturing camshafts and complete steering systems. Since 1979, the company's tool manufacturing division has manufactured tools for in-house production, particularly components for impact extruding, such as dies or components for lever-type facilities.

The work piece material is tool steel with a tensile strength of 120,000 - 184,000 psi--a very hard and challenging material for both machines and inserts.

Two-Part Tool-Life

When roughing a holder of high-alloy tool steel for a lever-type device, the existing cutter experienced a tool-life of only two components. "We tested several cutting parameter combinations; but the inserts were damaged after a short time and the inserts had to be exchanged frequently. That was unacceptable," says Thomas Knechtle, tool making coach at Presta.

Knechtle decided to test the Walter Xtra-tec shoulder milling cutter for profile and slot milling operations. To rough the holder, two cutter sizes are required--1" for the profile, and 0.787" for the slot, on a Deckel Maho DMC 60T machine.


During profile milling, the Walter inserts needed to be indexed or changed after an average of seven work pieces, while running at increased cutting parameters of [v.sub.c] = 410 fpm and [v.sub.f] = 27.5 ipm; the depth of cut of 0.080" remains unchanged.

Slot milling the complete batch of 20 work pieces at [v.sub.c] = 400 fpm and [v.sub.f] = 27.5 ipm never required indexing. In contrast, the previous tool's inserts were worn and damaged after milling only five components. "We were immediately impressed by the increase in tool life achieved with the new milling cutters, which clearly exceed our expectations," Knechtle recalls.

Tool-Life Increase

"The increase in tool life depends on the type of operation. The [Walter] F4042 cutter excels in profile milling the tongs holders," advises Ernst Gantenbein, Walter field sales engineer and customer advisor to Presta. "Using Xtra-tec cutters generally increases tool life by a factor of 2 - 3."

According to Knechtle and his team, an increase in tool life and process reliability is key to any success. Considering the relatively small number of components (about 50 - 60 holders/year), a decrease in machining time is not a top priority. Nevertheless, a high amount of non-productive time can be saved: The process continually runs, since less inserts need to be indexed and/or changed. "In addition, consistently high quality can be achieved along with high tool life," points out Andreas Morak, machining engineer at Presta.


Whether the present machining parameters will be changed remains to be decided. "It's possible that the parameters can be further optimized," says Gantenbein. Currently, the machines have reached their performance limit with existing tools. However, the new Xtra-tec cutters, which feature high positive geometry, do excel in soft cutting actions, which decrease machine vibrations. "This is amazing considering that the F4042 cutter is fitted with only three teeth, as opposed to the four-tooth cutter ThyssenKrupp Presta had used prior to the F4042," he adds.

In addition to excellent running properties, the shoulder milling cutter provides still other benefits.

Because of its plunging capability, the cutter can be used for milling the slots and pockets frequently required in tool building. The inserts, which can be indexed twice, are very compact and can be used on cutters with a diameter of 3/8" and larger. The largest diameter is 6".

The F4042 cutter is recommended for all work piece materials and it can be fitted with two different CVD coated cutting materials--WKP25 and WKP35. "Due to its high tensile strength, the WKP35 grade is unparalleled for machining difficult tool steels," Gantenbein notes. Walter USA or Circle 204 for more information
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Title Annotation:CUTTING TOOLS
Publication:Modern Applications News
Date:Jul 1, 2005
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