Finishing First in Cast-Steel Machining

When a contract manufacturer prides itself on continual improvement to provide 100% customer satisfaction, every machining problem demands its fullest attention. To Ron Rosso, president of Nebraska Machine Products (NMP; Omaha), it's as simple as "not becoming complacent once we get the opportunity to serve our customers."

Nebraska Machine was founded by Jack Rosso in 1966, and is run today by Ron and his brother Dave. NMP is a specialty screw-machine product manufacturer that produces parts ranging in size from 1/32 to 10'' (0.79-254-mm) diam for the electronics and computer industries for the smaller parts, and the hydraulic, agricultural, oil field, and automotive industries for the larger parts. When its full complement of automatic machines are operating to capacity, Nebraska Machine processes 80-100 tons (72-90 t) of material a month.

Since the early 1980s, the company has offered CNC machining capability, as well as processes including cross-drilling, centerless grinding, broaching, silver-soldering, welding, assembly, and vibratory finishing. Materials processed include plastics, brass, aluminum, stainless alloys, and steel alloys.

Faced with a problem of re-cutting chips in machining a cast-steel valve application, Nebraska Machine turned to Iscar Metals Inc. (Arlington, TX) and machine-tool distributor Productivity Inc. (Omaha) and cutting-tool distributor John Day Co. (Omaha) for help in solving the problem.


The cast-steel application involved machining some 36,000 parts annually on an A-51 HMC from Makino (Mason, OH). Due to the overall length of the part and all the work that needed to be done on the ID, the process was leaving chips that were being re-cut, resulting in catastrophic failure and tool damage.

Other machining problems that had to be addressed included deep-hole drilling to a flat bottom with a 63 pin. (1.6µm) finish and a tight flatness callout that had to be achieved. There was also difficulty in maintaining consistent part finish, in holding tolerances, and in preserving tool life.

Jason Rosso, a tooling specialist from Iscar, along with Dave Atkinson, Iscar milling product manager, evaluated and worked on the applications in collaboration with Dave Nelson from Productivity and Roger Weatherill from John Day.

The 3'' (76-mm) face mill that was being used for facing all the external surfaces was producing large, stringy-type chips that entered the ID of the part and caused its rough bore to fail. Iscar's solution was the F45LN D3.00-09-1.OR-N-15 face mill with the LNMT 150608 ANTN MM IC908 insert running at 800 fpm (244 m/min), 1018 rpm, 0.028 ipr (0.71 mm/rev), and 28.5 ipm (724 mm/min).

Coolant blast was introduced to help remove the chips. The number of parts machined per insert-edge went from 500 with existing tooling to 1200 with the Iscar tooling. The number of parts-per-insert increased from 2000 to 4800.

Iscar then turned its attention to the rough-boring application, replacing existing tooling utilizing a BHR MB25-25 × 50 bore head, STI MB 25 × 6.39 shank, ISHR/IHCR rough-boring insert holder with Iscar's CCMT-2.1 IC 907. While running at 550 fpm (168 m/min), 1573 rpm, 0.0055 ipr (0.14 mm/rev) and 8.65 ipm (219 mm/min), the number of parts-perinsert went from 120 to 280. There was an approximate 50% cost savings with the new tooling versus the existing tooling.

Chip formation and evacuation were the most important issues. The DZ drill with a WOLH 2.5-1 insert performed the next sequence in completing the parts. A 1.312 DZ drill was used to rough out the bottom for the Iscar Multi-Master to finish and hold flatness to 0.002'' (0.05 mm) with a 63 ì in. finish. Existing tooling was able to drill 180 holes while the Iscar DZ drill made 300 holes, an increase of 40% more holes with a cost savings to NMP of more than 28%.

Success of the Iscar tooling was measured in terms of chip control and the predictability of tool life. The Iscar ITS bore IHRF with CCGT inserts were used to finish the bore due to the tight tolerances. The CCGT inserts doubled metal removal rates, while producing 200 parts-per-edge compared with 45 with the existing tooling. The new tooling resulted in a 50% cost savings to Nebraska Machine on this application.

In finishing the part, Iscar recommended using the Multi-Master eight-flute end-mill head. This head has a 30° helix with a 0.030'' (0.76-mm) radius running in this application at 550 fpm, 3361 rpm, 0.007 ipr (0.18 mm/rev), and 23.5 ipm (597 mm). The number of parts per insert went from 300 to 4000, resulting in a 74% cost savings to NMP on this application.

Using Iscar's Multi-Master family of tools with interchangeable carbide heads, Nebraska Machine is able to hold tighter tolerances on product dimensions and increase tool life. Circle 224


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