High-density workholding gears up: General Industry Coverage

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END USER: Straitline Components, (250) 655-6603, www.straitlinecomponents.com. CHALLENGE: Avoid wasting workpiece material to keep costs down while increasing productivity. SOLUTION: Low gripping-profile clamps that provide high-density workholding on a tombstone. SOLUTION PROVIDER: Mitee-Bite Products LLC, (800) 543-3580, www.miteebite.com

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Cross-country and downhill cyclists appreciate having durable, lightweight parts while manufacturers of those parts, such as Straitline Components, like to reduce waste and boost productivity. To reduce manufacturing costs, the Sidney, British Columbia, company tries to minimize the amount of material required for effective workholding, but found throughput suffered because of its previous workholding method.

The parts include pedals, stems, sprockets, rotary hydraulic couplings, bash rings and chain-guide devices—practically any machinable aftermarket bike part, noted D.J. Paulson, general manager for Straitline.

In addition to producing its own brand of bike parts, Straitline is a job shop that serves an array of industries, from aerospace to oceanographic instrumentation. The company began producing its own bike parts to help ride out the business cycles of its customers. “We needed something to fill in the gaps without finding new machining customers, and we figured we could just create our own products,” Paulson said, noting that its bike part business represents 60 percent of Straitline’s work.

When previously making aluminum bike parts, the shop was holding workpieces in double-lock vises mounted on tombstones, but found it couldn’t hold them tightly enough to optimize roughing parameters without causing workpiece slippage and out-of-tolerance parts. “We could hold onto more material, but that just meant manufacturing costs went up,” Paulson said.

Figuring there must be a better way, the company sought alternatives and found Pitbull fixture clamps from Mitee-Bite Products LLC, Center Ossipee, N.H. The clamps provide a low gripping profile and high vertical and horizontal clamping forces, according to Mitee-Bite. For its aggressive stock-removal requirements, Straitline selected 0.750 “-wide clamps with a tool steel knife edge and maximum holding force of 3,600 lbs. It built a test fixture for the clamps and compared the clamp setup against the vise setup.

“The clamps can apply a tremendous amount of down force because of the way they cam down onto the part,” Paulson said, noting that the clamps only hold 0.090 ” of stock using a standard ¼-20 cap screw. “We found we could push the Mitee-Bite setup as hard as we wanted without the parts shifting in the fixture.”

Running a 1 “-dia. cutter at 14,000 rpm, Straitline can feed at about 250 ipm with a 3⁄8 ” DOC using the clamps vs. 100 ipm and 0.100 ” DOC using the vises, Paulson noted. “With the Mitee-Bites, we’re just flying through the material,” he said.