Threaded – headed fastener – or washer making: process and apparat – Process – Making externally threaded fastener – e.g. – screw or bolt
Patent
1991-04-05
1992-12-15
Larson, Lowell A.
Threaded, headed fastener, or washer making: process and apparat
Process
Making externally threaded fastener, e.g., screw or bolt
411387, B12H 302
Patent
active
051711869
ABSTRACT:
A method for forming a self-drilling screw. The self-drilling screw formed by this method stabilizes the screw during the hole drilling step of driving the screw and produces a precisely dimensioned hole for receiving the threaded portion of the screw. The method of forming the self-drilling screw starts with providing a screw blank having a head end and a tip. A driving head is formed on the head end and a drilling portion is formed on the shank distal the head end. Two longitudinally extending flutes are formed on the drilling portion of shank from the tip towards the head end. Each flute includes a working edge and a formed trailing edge. The working edges and the formed trailing edges of the two flutes are respectively diametrically opposed on the shank. A formed trailing diameter measured across the diametrically opposed formed trailing edges is greater than a working diameter measured across the diametrically opposed working edges. Next, the drilling portion is rolled between two oppositely moving complementary rolling dies for rolling the formed trailing edges inwardly. Rolling the formed trailing edges on the drilling portion forms rolled trailing edges. After rolling the drilling portion, a rolled trailing diameter measured across the rolled trailing edges substantially equals the working diameter. Finally, thread are formed on the shank generally between the head end and drilling portion.
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Larson Lowell A.
McKeon Michael J.
Textron Inc.
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