ISO 68-2:2023 PDF

Name: ISO 68-2:2023 — ISO general purpose screw threads — Basic and design profiles — Part 2: Inch screw threads
SKU: ISO 68-2:2023
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ISO general purpose screw threads — Basic and design profiles — Part 2: Inch screw threads

Название (английский):

ISO 68-2:2023

ISO general purpose screw threads — Basic and design profiles — Part 2: Inch screw threads

Статус документа:: Действующий
Формат:: Электронный (PDF)
Количество страниц:: 8
Дата публикации:: 5 октября 2023 г.
Издание:: ISO IS 68 edition 2 version 1
ICS:: 21.040.20

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Описание (английский):

This document specifies the basic and design profiles for ISO inch screw threads (UN and UNR). UN applies to both internal and external threads. UNR only applies to external threads. A flat or rounded root contour, due to the threading process, is specified for UN threads, while only a defined rounded root contour is specified for UNR external threads. This document is applicable to the inch fastening screw threads.

Abstract

Похожие стандарты

Стандарты, упомянутые в описании

Overview

ISO 68-2:2023 defines the basic and design profiles for ISO inch screw threads (UN and UNR). It is part of the ISO 68 series and applies specifically to inch fastening screw threads. The standard establishes the geometric form, key dimensional formulae and root/crest contour requirements used by designers, manufacturers and inspection personnel when working with UN (internal and external) and UNR (external only) threads.

Key topics and technical requirements

Thread types covered: UN (internal and external) and UNR (external threads only).

Basic profile: a common profile for internal and external threads; dimensions are derived from the fundamental triangle height H and pitch P. Example formulae included in the standard:

H = 3/(2n) = 0.86602540 / n (where n = threads per inch)
P = 1/n

Design profile: separate profiles for internal and external threads with defined thread heights and root radii:

External thread design height h = 17H/24 = 0.61343466 / n
Root radius R = H/6 = 0.14433757 / n

Root and crest contour rules:

UN threads: a flat root contour is specified by default but fully or partially rounded roots (unspecified size) are permitted because of the threading process.
UNR threads: require a defined rounded root contour. The root radius must be not less than 0.10825318·P (H/8) and for fully rounded roots not more than 0.14433757·P (H/6).
Internal threads: flat root contour; may be fully or partially rounded and cleared beyond the P/8 flat width.

Dimension rounding and consistency: dimensions are rounded per ASME B1.30 practice; the standard includes inch and converted metric tables (informative).

Practical applications and users

ISO 68-2:2023 is used where consistent inch thread geometry is required, including:

Fastener manufacturers and suppliers specifying UN/UNR thread form and root shapes

Mechanical designers and CAD/CAM engineers creating parts with inch screw threads

Tooling and thread cutting tool makers selecting tool profiles and root relief

Quality, inspection and metrology teams verifying thread dimensions and conformity

Standards committees and procurement professionals referencing thread geometry for product specifications

The standard helps improve interchangeability, reduce tool wear (rounded roots), and increase fatigue strength of external threads.

Related standards

ISO 68 series (other parts covering metric and other thread families)

ISO 5408 - Screw threads vocabulary (normative reference)

ASME B1.30 - Rounding and calculation practices referenced for dimensional rounding

Keywords: ISO 68-2, inch screw threads, UN threads, UNR threads, basic profile, design profile, thread root radius, fastening screw threads, thread dimensions.

ISO 68-2:2023 PDF

Abstract

Похожие стандарты

Overview

Key topics and technical requirements

Practical applications and users

Related standards

Технические детали

BS ISO 6813:1998

Road vehicles. Collision classification. Terminology

ISO 5408:1983

Cylindrical screw threads — Vocabulary

SIST ISO 6820:1997

Wheat flour and rye flour -- General guidance on the drafting of bread-making tests