The Horkos RM70H "near-dry" machine drills deep holes at penetration rates up to 10 higher than gundrilling.
U.S. automakers are turning to minimum-quantity-lubrication (MQL) technology to drill troublesome oil holes in forged-steel crankshafts. These holes typically measure 0.24 in. in diameter and nearly 4-in. deep — a 16:1 aspect ratio. Horkos Corp., which supplies such systems, reports that its RM70H "neardry" machines complete these deep holes at penetration rates up to 10 higher than gundrilling, while requiring just 1.7 oz/hr of fluid flow as compared to 16 gallon/min.
"Though the technology may be relatively new to the U.S., it's well proven elsewhere," explains Mark Ostraff, U.S. sales manager for Marubeni America Corp., Canton, Mich., the trading company for Horkos machines. He says that companies replacing gundrilling with near-dry machining report higher throughput, better process economics, and cleaner, safer operations.
The Horkos near-dry-drilling method uses a coated-carbide drill, mixes cutting fluid with air inside the machine spindle, and employs a special production fixture that efficiently sheds chips with no need for fluid to flush them away. The fixture also orients the crankshafts for processing of all holes in a single setup.
The process creates tiny curled chips that are easily evacuated, leaving a clean, straight hole and protecting the twist drill from chip binding and packing. The 99-to-1 reduction in cutting fluid also eliminates the need for bulky reservoirs and plumbing to store and recycle fluids.