Movatterモバイル変換

[0]ホーム
URL:

Jump to content
WikipediaThe Free Encyclopedia
Search

ISO metric screw thread

From Wikipedia, the free encyclopedia
Hardware threading standard

This articlemay be too technical for most readers to understand. Pleasehelp improve it tomake it understandable to non-experts, without removing the technical details.(December 2020) (Learn how and when to remove this message)

TheISO metric screw thread is the most commonly used type of general-purposescrew thread worldwide.[1] They were one of the firstinternational standards agreed when theInternational Organization for Standardization (ISO) was set up in 1947.[citation needed]

The "M" designation for metricscrews indicates thenominal outerdiameter of the screw thread, inmillimetres. This is also referred to as the "major" diameter in the information below. It indicates the diameter of smooth-walled hole that an externally threaded component (e.g. on abolt) will pass through easily to connect to an internally threaded component (e.g. anut) on the other side. For example, an M6 screw has a nominal outer diameter of 6 millimetres and will therefore be a well-located, co-axial fit in a hole drilled to 6 mm diameter.

Basic profile

[edit]
Basic profile of all ISO metric screw threads, where the male part has the external thread

The design principles of ISO general-purpose metric screw threads ("M" series threads) are defined in international standard ISO 68-1.[2] Each thread is characterized by itsmajor diameter,D (Dmaj in the diagram), and itspitch,P. ISO metric threads consist of a symmetric V-shaped thread. In a cross-section along the thread axis, the sides of the V have an angle of 60° to each other. The thread depth is 0.54125 × pitch. The outermost1⁄8 and the innermost1⁄4 of the heightH of the V-shape are cut off from the profile.

The relationship between the heightH and the pitchP is found using the following equation whereθ is half the included angle of the thread, in this case 30°:[3]

H=1tan⁡θ⋅P2=32⋅P≈0.8660⋅P{\displaystyle H={\frac {1}{\tan \theta }}\cdot {\frac {P}{2}}={\frac {\sqrt {3}}{2}}\cdot P\approx 0.8660\cdot P}

or

P=2tan⁡θ⋅H=23⋅H≈1.1547⋅H{\displaystyle P=2\tan \theta \cdot H={\frac {2}{\sqrt {3}}}\cdot H\approx 1.1547\cdot H}

Because only5⁄8 of this height is cut, the difference between major and minor diameters is5⁄4 × 0.8660 ×P = 1.0825 ×P, so thetap drill size can be approximated by subtracting the thread pitch from the major diameter.

In an external (male) thread (e.g. on a bolt), the major diameterDmaj and the minor diameterDmin definemaximum dimensions of the thread. This means that the external thread must end flat atDmaj, but can be rounded out below the minor diameterDmin. Conversely, in an internal (female) thread (e.g. in a nut), the major and minor diameters areminimum dimensions; therefore the thread profile must end flat atDmin but may be rounded out beyondDmaj. In practice this means that one can measure the diameter over the threads of a bolt to find the nominal diameterDmaj, and the inner diameter of a nut isDmin.

The minor diameterDmin and effective pitch diameterDp are derived from the major diameter and pitch as

Dmin=Dmaj−2⋅58⋅H=Dmaj−538⋅P≈Dmaj−1.082532⋅PDp=Dmaj−2⋅38⋅H=Dmaj−338⋅P≈Dmaj−0.649519⋅P{\displaystyle {\begin{aligned}D_{\text{min}}&=D_{\text{maj}}-2\cdot {\frac {5}{8}}\cdot H=D_{\text{maj}}-{\frac {5{\sqrt {3}}}{8}}\cdot P\approx D_{\text{maj}}-1.082532\cdot P\\[3pt]D_{\text{p}}&=D_{\text{maj}}-2\cdot {\frac {3}{8}}\cdot H=D_{\text{maj}}-{\frac {3{\sqrt {3}}}{8}}\cdot P\approx D_{\text{maj}}-0.649519\cdot P\end{aligned}}}

Tables of the derived dimensions for screw diameters and pitches defined in ISO 261 are given inISO 724.

Designation

[edit]

A metric ISO screw thread is designated by the letter M followed by the value of the nominal diameterD (the maximum thread diameter) and the pitchP, both expressed in millimetres and separated by a dash or sometimes the multiplication sign,× (e.g. M8-1.25 or M8×1.25). If the pitch is the normally used "coarse" pitch listed in ISO 261 or ISO 262, it can be omitted (e.g. M8).[4]: 17 

The length of amachine screw or bolt is indicated by an× and the length expressed in millimetres (e.g. M8-1.25×30 or M8×30).[5]

Tolerance classes defined inISO 965-1 can be appended to these designations, if required (e.g. M500– 6g in external threads). External threads are designated by lowercase letter, g or h. Internal threads are designated by upper case letters, G or H.[4]: 17 

Preferred sizes

[edit]
See also:Preferred metric sizes § ISO_261 and 262 fastener diameters

ISO 261 specifies a detailed list of preferred combinations of outer diameterD and pitchP for ISO metric screw threads.[6][7]ISO 262 specifies a shorter list of thread dimensions – a subset of ISO 261.[8]

ISO 262 selected sizes for screws, bolts and nuts
Nominal diameter (mm)SeriesPitch (mm)Nominal diameter (mm)SeriesPitch (mm)
CoarseFineCoarseFine
1R100.250.2︙
1.2R100.250.216R1021.5
1.4R200.30.218R202.52 or 1.5
1.6R100.350.220R102.52 or 1.5
1.8R200.350.222R202.52 or 1.5
2R100.40.2524R1032
2.5R100.450.3527R2032
3R100.50.3530R103.52
3.5R200.60.3533R203.52
4R100.70.536R1043
5R100.80.539R2043
6R1010.7542R104.53
7R2010.7545R204.53
8R101.251 or 0.7548R1053
10R101.51.25 or 152R2054
12R101.751.5 or 1.2556R105.54
14R2021.560R205.54
︙64R1064

The thread values are derived from roundedRenard series. They are defined in ISO 3, with "1st choice" sizes being from the Rˈˈ10 series and "2nd choice" and "3rd choice" sizes being the remaining values from the Rˈˈ20 series.[6]

Thecoarse pitch is the commonly used default pitch for a given diameter. In addition, one or two smallerfine pitches are defined, for use in applications where the height of the normalcoarse pitch would be unsuitable (e.g. threads in thin-walled pipes). The termscoarse andfine have (in this context) no relation to the manufacturing quality of the thread.[9]

In addition to coarse and fine threads, there is another division of extra fine, orsuperfine threads, with a very fine pitch thread. Superfine pitch metric threads are occasionally used in automotive components, such as suspension struts, and are commonly used in the aviation manufacturing industry. This is because extra fine threads are more resistant to coming loose from vibrations.[10] Fine and superfine threads also have a greaterminor diameter than coarse threads, which means the bolt or stud has a greater cross-sectional area (and therefore greater load-carrying capability) for the same nominal diameter.

Heritage pre ISO DIN sizes

[edit]
Obsolete DIN sizes
for historical purposes
DIN 13, Din 13-1[11][12][13]
Nominal diameter (mm)Pitch (mm)Nominal diameter (mm)Pitch (mm)
CoarseFineCoarseFine
1.10.25-︙
1.70.35-4.50.75-
2.20.4 ?-5.50.9-
2.30.4-91.25-
2.60.45-111.5-
︙152-

Japanese pre 1967 heritage heritage standard

[edit]

Japan had aJIS metric screw thread standard that largely followed the ISO, but with some differences in pitch and head sizes.In April 1967 the JIS (Japanese Industrial Standard) was changed to match the screw pitches of the ISO standard. It may help explain why some metric screws don't seem to fit on one's motorcycle or car.[14]

JIS pre April 1967 screw pitches with post April 1967 ISO screw pitches
Nominal
diameter
(mm)		Pitch
(mm)		ISO
Pitch
(mm)
30.60.5
40.750.7
50.90.8
61.01.0
81.001.25
101.251.5
121.51.75

Spanner (wrench) sizes

[edit]

Below are some common spanner (wrench) sizes for metric screw threads. Hexagonal (generally abbreviated to "hex") head widths (width across flats, spanner size) are forDIN 934 hex nuts[15] and hex head bolts. Other (usually smaller) sizes may occur to reduce weight or cost, including the small series flange bolts defined in ISO 4162[16] which typically have hexagonal head sizes corresponding to the smaller first choice thread size (for example, M6 small series flange bolts have 8 mm hexagonal heads, as would normally be found on M5 bolts).[17]


Thread		Spanner (wrench) size (mm)

Hex nut,
and bolt
Socket-head cap screw
  • Button-head cap screw
  • Counter-sunk
    flat-head cap screw

Set,
or grub,
screw
ISODIN
M1-2.5---
M1.2-3---
M1.4-31.25-0.7
M1.63.21.50.90.7
M241.51.250.9
M2.5521.51.3
M35.52.521.5
M3.56---
M4732.52
M58432.5
M610543
M711---
M813654
M101617865
M1218191086
M14212210--
M162414108
M18271412-
M2030171210
M2234321714-
M2436191412
M2741191714
M3046221714
M335024--
M365527--
M3960---
M426532--
M4570---
M487536--
M528036--
M568541--
M6090---
M649546--

[citation needed]

Standards

[edit]

International

[edit]
  • ISO 68-1: ISO general purpose screw threads — Basic profile — Metric screw threads.
  • ISO 261: ISO general purpose metric screw threads — General plan.
  • ISO 262: ISO general purpose metric screw threads — Selected sizes forscrews, bolts andnuts.
  • ISO 965: ISO general purpose metric screw threads —Tolerances[4]
    • ISO 965-1: Principles and basic data
    • ISO 965-2: Limits of sizes for general purpose external and internal screw threads.
    • ISO 965-3: Deviations for constructional screw threads
    • ISO 965-4: Limits of sizes for hot-dip galvanized external screw threads to mate with internal screw threads tapped with tolerance position H or G after galvanizing
    • ISO 965-5: Limits of sizes for internal screw threads to mate with hot-dip galvanized external screw threads with maximum size of tolerance position h before galvanizing

National

[edit]

See also

[edit]

References

[edit]
  1. ^ISO/TC/ 1 Business Plan, 2007-03-05, Version 1.3. Table 3: The market share of each screw thread, p. 7.
  2. ^ISO 68-1:1998 ISO general purpose screw threads – Basic profile – Part 1: Metric screw threads. International Organization for Standardization.
  3. ^Oberg et al. 2000, p. 1706
  4. ^abcISO 965-1:2013 ISO general purpose metric screw threads — Tolerances — Part 1: Principles and basic data. International Organization for Standardization. 15 September 2013.
  5. ^"ISO 8991:1986 - Designation system for fasteners".International Organisation for Standardization.
  6. ^abISO 261:1998 ISO general purpose metric screw threads – General plan. International Organization for Standardization. 17 December 1998.
  7. ^ISO & DIN13
  8. ^ISO 262:1998 ISO general purpose metric screw threads – Selected sizes for screws, bolts and nuts. International Organization for Standardization. 17 December 1998.
  9. ^"Technical Data Section - Coarse vs. Fine Pitch Threads".Belmey Industrial Supplies. Retrieved20 October 2025.
  10. ^"Final report"(PDF).ntrs.nasa.gov. Archived fromthe original(PDF) on 14 March 2017. Retrieved7 July 2017.
  11. ^Gewindetabellen 15, page 519
  12. ^Valvias
  13. ^Early Metric Systems
  14. ^"Machine Screws - Pan Head - Metric - JIS Zinc Pre ISO Coarse Pitch - Classic Fasteners".www.classicfasteners.com.au. Retrieved31 October 2025.
  15. ^Hex nuts
  16. ^bolts
  17. ^"ISO 4162:2012".International Organization for Standardization. Retrieved23 December 2022.

Bibliography

[edit]

External links

[edit]


1–9999
10000–19999
20000–29999
30000+
Retrieved from "https://en.wikipedia.org/w/index.php?title=ISO_metric_screw_thread&oldid=1323060759"
Categories:
Hidden categories:
[8]ページ先頭
©2009-2025 Movatter.jp