ISO 3161:1999

This International Standard specifies the general requirements and limit dimensions of inch series UNJ threads with

controlled root radius for aerospace construction.

It determines the basic triangular profile for this type of thread and gives a system for designating the diameter and

number of threads per inch combinations. For all diameters 0,060 in (1,524 mm) to 6,000 in (152,4 mm), it offers in

the form of tables the basic dimensions and tolerances for a selection of diameter and number of threads per inch

combinations. It also provides the method of calculation for the dimensions and tolerances for any diameter and

number of threads per inch combination not given in the tables, including threads with a diameter in excess of

6,000 in.

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• mandatory clauses to satisfy,
• non-essential but useful clauses to know, such as permissions and recommendations.

The identification of these types of clauses is based on the document "ISO/IEC Directives, Part 2 - Principles and rules of structure and drafting of ISO documents" as well as on a constantly enriched list of verbal forms.

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