Turning and hobbing combined

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END USER: Mercury Marine, (920) 929-5000, www.mercurymarine.com. CHALLENGE: To increase productivity when machining driveshafts and propeller shafts. SOLUTION: A lathe with a hob assembly. SOLUTION PROVIDERS: Okuma America Corp., (704) 588-7000, www.okuma.com

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With more than 70 years in the industry, Mercury Marine has maintained its leading market position with constant innovation, foresight and the latest technology. These characteristics are shown throughout 220,000-sq.-ft. Plant 4 in Fond du Lac, Wis., where Mercury Machine produces high volumes of driveshafts and propeller shafts for outboard and stern-drive marine propulsion systems. The plant has about 220 employees and contains 15 to 20 Okuma lathes of various types and vintages.

Mercury turns the driveshaft blanks on a twin-spindle LT10 Okuma lathe, without live tooling. The machined shafts are then manually transferred to a Gleason P60 hobbing machine to cut the splines.

Mercury Marine’s Okuma LB3000 EX BB MYW800 is equipped with a Wes-Tech overhead gantry for loading and unloading shafts. Image courtesy Okuma America.

Recently, Mercury added a LB3000 EX BB MYW800 from Okuma America Corp., Charlotte, N.C., which has live tools, a Y-axis with 5″ of travel, a W-axis subspindle and a hob assembly from WTO Inc., Charlotte. The new machine produces a complete driveshaft in 3 to 4 minutes. It is equipped with a Wes-Tech overhead gantry for loading and unloading shafts.

A close-up view of the hobbed pinion spline. It is a ¾” spline that rises to a taper, at which point the pinion gear is mounted. Image courtesy Okuma America.

“In the main spindle, we start with a blank that has been carburized,” said Kurt Lefeber, a Mercury process engineer. “We turn some of that carburizing off, giving greater definition to the part shape. We rough and finish one end and then transfer the shaft to the subspindle, where it’s roughed, finished, center-drilled and hobbed.”

Okuma has a unique method of transferring a shaft from the main spindle to the subspindle. There’s a pneumatic pusher system inside the main spindle, so when the gantry places a raw piece into the spindle, the piece goes to a backstop. The backstop has an air cylinder with a piston. When the first operation is finished, an M code in the control fires the air cylinder, which pushes the shaft out of the main spindle and transfers it to the subspindle.