The buzz on a new nut
Choosing between heavy-duty threaded fasteners and swaged lockbolts has never been easy. Conventional nuts and bolts have the familiarity factor going for them, and they mostly require only an ordinary wrench for both assembly and disassembly. Lockbolts don't come apart easily, which is exactly their appeal. So why choose at all? Huck Fasteners recently developed a patent-pending threaded fastener that combines the best of both approaches.
Called the BuzzNut, this patent-pending fastener employs a new two-piece nut consisting of a round locking collar atop an essentially standard hex nut body. Prior to tightening, interlocking wedge features hold the two pieces together loosely, leaving a 0.040-inch gap between them. Tightening, however, drives the nut body into the locking collar, whose internal threads then deform into the bolt threads. "We call it a self-swaging process," explains Jim Hutchison, Huck's business development manager.
The two-piece nut is what gives the new fastener its dual nature. Like a conventional threaded fastener, the BuzzNut installs and disassembles with ordinary shop tools. And like a swaged lockbolt, the BuzzNut provides plenty of holding power. Hutchison places the BuzzNut's strength values at 33,900 lbs tensile, 24,000 lbs clamp, and 27,500 lb shear.
Because the gap between the BuzzNut's body and locking collar disappears only at the pre-determined clamp threshold (24,000 lbs), the new fastener shows that the bolt has reached its proper preload. "It acts much like a direct tension indicating washer," Hutchison notes. Users don't need gauges to verify the gap's disappearance thanks to a visual indicator-a dark coloration that burnishes away once the gap fully closes. "As soon as you can see the bright spot on the base, the fastener is perfectly tightened," Hutchison says.
The BuzzNut works with a custom bolt whose threads have been optimized for the swaging process.
Jim Hutchison, Huck Fasteners, 8001 Imperial Dr., Waco, TX 76714-8117; Tel: (254) 751-5235; Fax: (254) 751-5259; www.huck.com