Changing tools to achieve tolerances

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END USER: Richardson Manufacturing Co., (217) 546-2249, www.rmc-bigcnc.com. CHALLENGE: Achieve a tight tolerance without increasing cycle time. SOLUTION: A combination drill that eliminated an unreliable boring operation. SOLUTION PROVIDER: Allied Machine & Engineering Corp., (800) 321-5537, www.alliedmachine.com

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Richardson Manufacturing Co. provides machining services to heavy equipment, mining and oil field customers and operates 24/7 at its 125,000-sq.-ft. facility in Springfield, Ill. RMC, which employs more than 220 workers, has more than 40 CNC machine tools, including vertical and horizontal lathes with live tooling, vertical and horizontal machining centers, and gear shaping and hobbing machines.

One part that RMC makes is a wheel-hub adapter for a mining truck. “At about 40 pieces per month, the volume is low to medium by our standards,” said Brad Albrecht, manufacturing engineering manager. Because the hub adapter only requires drilling, machining it on a HMC using through-coolant at 40 psi is relatively simple compared to other parts RMC makes, according to Albrecht. “Most of our parts require multiple turning and milling operations in a combination of vertical or horizontal lathes and machining centers,” he said.

However, the part, which is made of modified 4140 steel, requires a considerable amount of holemaking. It has 57 1.362 “-dia., 2½ “-deep through-holes and 54 1.438 “-dia., 4½ “-deep through-holes.

RMC was applying three cutting tools to complete each of the 57 holes: a drill, a twin boring bar and a chamfer mill. The challenge was consistently achieving the tolerance while maintaining the production rate, Albrecht noted. “The ±0.002 ” tolerance was too tight for the twin boring bar setup we were using, and we were having trouble holding size,” he said. “We thought about going to single-point boring or reaming, but didn’t want to increase cycle time.”

(The 54-hole pattern in the hub adapter is drilled with an indexable-insert drill, which is able to achieve its 0.020 “/ -0.010 ” tolerance without a problem.)

Courtesy of Richardson Manufacturing