BS ISO 3353-1:2020 pdf download – Aerospace — Lead and runout threads Part 1: Rolled external threads
This document specifies the lead and runout requirements for rolled external threads for aerospace construction, and the inspection method to be used in case of dispute.
It is applicable whenever it is referenced in a definition document.
2 Normative references
There are no normative references in this document.
3? Terms? and? definitions
For the purposes of this document, the following terms and definitions apply.
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lead thread
portion of the incomplete thread that is fully formed at the root but not at the crest which occurs at the beginning end of either external or internal threads
runout thread
part of the screw thread in which is located the thread incompletely formed during rolling, between the completely formed threads and the part which has not been rolled
completely formed thread
thread, the profile of which (ABC) is located, over an axial distance of 1P, within the limits specified in the definition document for the thread
Note 1 to entry: See Figure 1.
4 Symbols for threads
d the major diameter of the thread
d 2 the pitch diameter of the thread
d 3 the minor diameter of the thread
P the thread pitch
5 Requirements
5.1 General requirements
The flanks at the root of the incompletely formed threads shall be joined by a radius or by two radii and a flat, that are smooth and devoid of abrupt tool marks. This radius, or these radii and the radius r (see Figure 3 to Figure 9) shall be greater than or equal to the minimum root radius specified for the complete threads in the definition document for the thread.
5.2 Lead threads
See Figure 2.BS ISO 3353-1 pdf download.