ALMA Resources

Technical Publications

Conformance of Roll Formed Internal Threads to AS8879

Use of the roll forming process for the creation of internal threads has been and remains a viable method for producing internally threaded fasteners. The roll forming method uses a tool similar to a tap, but one without cutting edges. The geometry of the tool initiates material flow to fill the tool geometry, but typically leaves an incomplete minor diameter. Thread forms exhibiting this condition are typically referred to as having “open crests.”

Historically, in the aerospace fastener industry, the method commonly employed in production of structural products referencing the AS8879 thread specification has been cutting of threads from a prepared hole at the AS8879 specified minor diameter. There are various methods available to create cut threads.

Products & Characteristics

The Aircraft Locknut Manufacturer's Association (ALMA) is comprised of the leading North American manufacturers of self-locking nuts for the aerospace industry. The Association works closely with other national and international military and industry technical organizations in developing specifications, standards, and other technical practices. Several member companies participated as task group members and technical resource personnel in the preparation of the Industrial Fastener Institute's handbook "Recommended Practices for Statistical Process Control".

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